Using the OSPF Protocol

This document describes the Open Shortest Path First (OSPF) protocol.

Routers that use a common routing protocol form an autonomous system (AS). This common routing protocol is called an Interior Gateway Protocol (IGP). Your OpenROUTE Networks router supports two IGPs, OSPF and RIP (Routing Information Protocol). IGPs dynamically detect your router's ability to reach a network and routing information within an AS and use this information to build the IP routing table. IGPs can also import external routing information into the AS.

OpenROUTE Networks routers can run OSPF and RIP simultaneously. When you configure your router to do this, OSPF routes are preferred. OSPF provides services not available with RIP. In general, OpenROUTE Networks recommends using the OSPF protocol due to its robustness, responsiveness, and decreased bandwidth requirements.

OSPF is based on link-state technology or the shortest-path first (SPF) algorithm. RIP is based on the Bellman-Ford or the distance-vector algorithm.

This document contains the following sections:

Introducing OSPF

Configuring OSPF

OSPF Commands

Introducing OSPF

OpenROUTE supports a complete implementation of the OSPF routing protocol as specified in RFC 1583 (Version 2) and also certain new capabilities specified in RFC 2178. Version 2 is incompatible with routers running OSPF version 1. OSPF information is not exchanged between routers running version 1 and version 2.

OSPF is a link state dynamic routing protocol that detects and learns the best routes to (reachable) destinations. It can quickly perceive changes in the topology of an AS and, after a short convergence period, calculate new routes. The OSPF protocol does not encapsulate IP packets but forwards them based on destination address only.

OSPF Features

OSPF features include the following:

Least Cost Routing. Allows you to configure path costs based on any combination of network parameters. For example, bandwidth, delay, and dollar cost.
No limitations to the routing metric. While RIP restricts the routing metric to 16 hops, OSPF has no restriction.
Multipath Routing. Allows you to use multiple paths of equal cost that connect the same points. You can then use these paths for load balancing, resulting in more efficient use of network bandwidth.
Area Routing. Decreases the resources (memory and network bandwidth) consumed by the protocol and provides an additional level of routing protection.
Variable Length Subnet Masks. Allow you to break an IP address into variable size subnets, conserving IP address space.
Routing Authentication. Supports MD5 authentication.
Point-to-Multipoint. Override the default OSPF interface type and then select point-to multipoint as the OSPF interface type override.

OSPF Interface Types

OSPF supports the following interface types:

Point-to-Point. Networks that use a communication line to join a single pair of routers. For example, a 56 Kb serial line that connects two routers.
Point-to-Multipoint. Networks that support a communication line to join a single router with multiple routers. For example, a Frame Relay network.
Broadcast. Networks that support more than two attached routers and are capable of addressing a single physical message to all attached routers. For example, an Ethernet network.
Non-Broadcast. Networks that support more than two attached routers but have no broadcast capabilities, such as a Frame Relay network. For OSPF to function properly, this network requires extra configuration information about other OSPF routers attached to the non-broadcast network.

OSPF Routers

There are two special kinds of OSPF routers, area border routers and AS boundary routers.

Area Border Routers. A router attached to multiple areas that runs multiple copies of the basic algorithm, one copy for each attached area and an additional copy for the backbone. Area border routers condense the topology information of attached areas for distribution to the backbone. The backbone then distributes this information to other areas.
AS Boundary Routers. A router that exchanges information with routers that belong to other ASs. These routers import this information to the OSPF routing domain in AS external link advertisements.

OSPF Routing Summary

When a router is initialized, it uses the Hello Protocol to send hello packets to its neighbors, and they in turn send their packets to the router. On broadcast and point-to-point networks, the router dynamically detects its neighboring routers by sending the Hello packets to the multicast address ALLSPFRouters; on non-broadcast networks you must configure information to help the router discover its neighbors. On all multi-access networks (broadcast and non-broadcast), the Hello Protocol also elects a designated router for the network.

The router then attempts to form adjacencies with its neighbors to synchronize their topological databases. Adjacencies control the sending and receiving of the routing protocol packets, as well as the distribution of the topological database updates. On a multi-access network, the designated router determines which routers become adjacent.

A router periodically advertises its status or link state to its adjacencies. Link state advertisements flood throughout an area ensuring that all routers have exactly the same topological database. This database is a collection of the link state advertisements received from each router belonging to an area. From the information in this database, each router can calculate a shortest path tree with itself designated router as the root. Then the shortest path tree generates the routing table.

Designated Router

Every multi-access network has a designated router that performs two main functions for the routing protocol, it originates network link advertisements and it becomes adjacent to all other routers on the network.

When a designated router originates network link advertisements, it lists all the routers, including itself, currently attached to the network. The link ID for this advertisement is the IP interface address of the designated router. By using the subnet/network mask, the designated router obtains the IP network number.

The designated router becomes adjacent to all other routers and is charged with synchronizing the link state databases on the broadcast network.

The Hello Protocol elects the designated router after determining the router's priority from the Rtr Pri field of the hello packet. When a router's interface first becomes functional, it checks to see if the network currently has designated router. If it does, it accepts that designated router regardless of that router's priority, otherwise, it declares itself the designated router. If the router declares itself the designated router at the same time another router does, the router with highest router priority (Rtr Pri) becomes the designated router. In the case that both Rtr Pris are equal, the one with the higher router ID is elected.

Once the designated router is elected, it becomes the endpoint for many adjacencies. On a broadcast network this optimizes the flooding procedure by allowing the designated route to multicast its Link State Update packets to the address ALLSPFRouters rather than sending separate packets over each adjacency.

Configuring OSPF

The following steps present the tasks required to get the OSPF protocol up and running:

: 1. Enable OSPF. In doing so, you must estimate the final size of the OSPF routing domain. See Enabling OSPF.
: 2. Define OSPF areas attached to the router. If you do not define OSPF areas, the router assumes there is a single backbone area. See Defining Backbone and Attached OSPF Areas.
: 3. Define the router's OSPF network interfaces. Set a collection of OSPF operating parameters. See Setting OSPF Interfaces.

The following steps present tasks that you may want to do:

If you want to forward IP multicasts (IP Class D addresses), enable IP multicast routing capability. See Enabling Multicast Forwarding.
If you want the router to import routes learned from other routing protocols (RIP, EGP, or statically configured routes), enable AS boundary routing and define whether routes are imported as Type 2 or Type 1 externals. See Enabling AS Boundary Routing.
If the router connects to non-broadcast networks, set the non-broadcast network parameters. This consists of a list of the other OSPF routers that are connected to the non-broadcast network.
If you want to boot a neighboring router over an attached point-to-point interface, configure the neighbor's IP address. This is done by defining non-broadcast parameters for the point-to-point interface.

The sections that follow explain each step in detail and include examples.

Enabling OSPF

Before you can enable OSPF, you must supply the total number of external routes and the total number of OSPF routers. These values estimate the final size of the OSPF routing domain and should be identical in all of your OSPF routers. Each router running OSPF has a database describing a map of the routing domain. This database is identical in all participating routers. From this database, the router builds the IP routing table through the construction of a shortest-path tree, with the router itself as root. The routing domain refers to an AS running the OSPF protocol.

To enable OSPF enter enable ospf and respond to the prompts:

OSPF Config>enable ospf
Estimated # external routes[0]? 200
Estimated # OSPF routers [0]? 60

Estimated # external routes—Total number of AS external routes that will be imported into the OSPF routing domain. A single destination may lead to multiple external routes when it is imported by separate AS boundary routers.

For example, if the OSPF routing domain has two AS boundary routers, both importing routes to the same 100 destinations, set the number of AS external routes to 200.
Estimated # OSPF routers—Total number of OSPF routers in the routing domain.

Defining Backbone and Attached OSPF Areas

Define the OSPF areas that are directly attached to the router. If you do not define any areas, the software assumes that all of the router's directly attached networks belong to the backbone area (area ID 0.0.0.0).

OSPF allows you to split the AS into regions called areas. OSPF areas are a collection of contiguous networks. The topology of any one area is hidden from that of the other areas. Hiding information significantly reduces routing traffic and protects routing within an area from outside influence.

A router has a separate database that contains the topology for each area to which it is connected. Two routers belonging to the same area have identical topologies for that area.

OSPF areas are defined as address ranges. External to the area, a single route is advertised for each address range. For example, if an OSPF area consists of all subnets of the class B network 128.185.0.0, the area consists of a single address range. The address range is specified as an address of 128.185.0.0 together with a mask of 255.255.0.0. Outside the area, the entire subnetted network is advertised as a single route to network 128.185.0.0.

Every OSPF routing domain must have a backbone. The backbone is a special OSPF area having an area ID equal to 0.0.0.0. The OSPF backbone must be contiguous; however, it is possible to define areas where the backbone is not physically contiguous. When this situation exists, you must configure a virtual link to maintain the backbone's connectivity. You can configure virtual links between any two backbone routers that have an interface to a common non-backbone area.

Figure 1 OSPF Areas

The backbone is responsible for distributing inter-area routing information. The backbone area consists of any of the following:

Networks belonging to Area 0.0.0.0
Routers attached to those networks
Routers belonging to multiple areas
Configured virtual links

To set the parameters for an OSPF area, use the set area command:

OSPF Config>set area
Area number [0.0.0.0]? 0.0.0.1

Authentication Type (0:NONE, 1:SIMPLE, 2:CRYPTOGRAPHIC) [0]? 1
Is this a stub area? [No]:

Area number is the OSPF area address. An OSPF area is a contiguous group of networks that is defined by a list of address ranges, each indicated by a combination of the IP address and an address mask. A network belongs to an area if its address is in the list.
Authentication type (security scheme) to be used in the area:

Type Meaning

0
No authentication necessary

1
A simple password

2
Cryptographic (MD5 authentication)
Stub area designation. If you enter Yes,
Note: You cannot configure the backbone as a stub area. External routing in stub areas is based on a default route. Each border area router attaching to a stub area originates a default route for this purpose. You can configure the cost of this default route using the OSPF set area command.

Type	Meaning
0	No authentication necessary
1	A simple password
2	Cryptographic (MD5 authentication)

OSPF Config>set area
Area number [0.0.0.0]? 0.0.0.2

Authentication Type (0:NONE, 1:SIMPLE, 2:CRYPTOGRAPHIC) [0]? 1
Is this a stub area? [No]: yes
Stub default cost [0]?
Import summaries? [Yes]:

Setting OSPF Interfaces

To set the OSPF parameters for the router's network interfaces, use the set interface command and then respond to the prompts.

You can dynamically change the cost of an OSPF interface from the router's monitoring environment. This new cost is flooded quickly throughout the OSPF routing domain and modifies the routing immediately. When you restart/reload the router, the cost of the interface reverts to the value in the saved configuration.

When responding to the prompts, supply the interface's IP address for each interface in the router and answer the questions that follow. For the parameters listed below you must enter the same value for all routers attached to a common network segment.

Hello interval
Dead router interval
Authentication key

The first prompt asks for the OSPF area to which the interface attaches. In the following example, suppose that the interface address mask is 255.255.255.0, indicating that the interface attaches to a subnet (128.185.138.0) of network 128.185.0.0. All other OSPF routers attached to subnet 128.185.138.0 must also have these parameters set to the same values.

OSPF Config>set interface
Interface IP address [0.0.0.0]? 128.185.123.75
Attaches to area [0.0.0.0]? 0.0.0.1
Retransmission Interval (in seconds) [5]?
Transmission Delay (in seconds) [1]?
Router Priority [1]?
Hello Interval (in seconds) [10]?
Dead Router Interval (in seconds) [40]?
Type Of Service 0 cost [1]? 5
Authentication Key?
Retype Auth. Key?
Message Digest Key ID [0]?
MD5 Key?
Retype MD5 Key?
Override the default OSPF interface-type? [No]: y
OSPF interface-type override
(1=broadcast, 3=NBMA, 5=point-to-multipoint) [0]? 3
Poll Interval [120]?
Forward multicast datagrams? [Yes]:
Forward as data-link unicasts? [No]:

Enabling Multicast Forwarding

To enable the routing of IP multicast (class D) datagrams, use the enable multicast command. The software prompts you on whether you want the router to forward multicasts between OSPF areas, as well as whether you want the router to forward multicasts between autonomous systems.

Multicasting is a LAN technique that allows copies of a single packet to pass to a selected subset of all possible destinations. Some hardware, for example Ethernet, supports multicast by allowing a network interface to belong to one or more multicast groups.

The IP protocol supports IP multicast routing through IP multicast extensions to OSPF (MOSPF). IP multicast is an extension of LAN multicasting to a TCP/IP Internet. This process lets an IP host send a single datagram (called an IP multicast datagram) that is delivered to multiple destinations. IP multicast datagrams are packets whose destinations are Class D IP addresses. Each Class D address defines a multicast group.

The Internet Group Management Protocol (IGMP) is the OSPF extension that lets an IP host participate in IP multicasting. IGMP lets routers keep track of IP group membership on its local LANs by sending IGMP Host Membership Queries and receiving IGMP Host Membership Reports.

An MOSPF router then distributes group location information throughout the routing domain by flooding a new type (type 6) of link state advertisement, the group-membership-LSA. This enables the MOSPF routers to efficiently forward a multicast datagram to its multiple destinations. This is done by each router calculating the path of the multicast datagram as a tree whose root is the datagram source and whose terminal branches are LANs containing group members.

While running MOSPF, multicast datagram forwarding works in the following ways:

While forwarding IP multicasts is not reliable, IP multicast datagrams are delivered with the same best effort as with the delivery of IP unicasts.
Multicast datagrams travel the shortest path between the datagram source and any particular destination (OSPF link state cost). This occurs because a separate tree is built for each datagram source and destination group pair.
A multicast datagram is forwarded as a data-link multicast at each hop. The Address Resolution Protocol (ARP) is not used. For some network technologies, mapping between Class D addresses and data-link multicast occurs while for others, Class D addresses are mapped to the data-link broadcast address.
When paths from the datagram source to two separate group members share an initial common segment, only a single datagram is forwarded until the paths go in separate directions. The path can split at either a router or at a network. If the path splits at a router, the router copies the packet before sending it. If the path splits at a network, the packet replicates through a data-link multicast.
You can use MOSPF routers with OSPF routers that do not support multicast extensions. In this configuration, all routers interoperate in the routing of unicasts. This lets you slowly introduce multicast capability into an internetwork.

Some configurations of MOSPF and non-MOSPF routers may produce unexpected failures in multicast routing.
You construct separate multicast paths in MOSPF for each TOS. However, routers do not support TOS-based routers. You can mix non-TOS routers with TOS-based routers, but this causes TOS to be ignored in the forwarding of multicasts.
You configure the router to send Simple Network Management Protocol (SNMP) traps to a multicast group address by adding a group address to a particular SNMP community name.

Entering enable multicast, enables multicast with default parameters on all OSPF interfaces. You can change the parameters using the OSPF set interface command.

OSPF Config>enable multicast
Inter-area multicasting enabled(Yes or No): yes
Inter-AS multicasting enabled(Yes or No): yes

By default the router does not forward IP multicast (class D) datagrams. To display the multicast parameters, use the list interfaces command. If multicast is disabled, the multicast parameters are not displayed.

Enabling AS Boundary Routing

To import routes learned from other protocols (RIP, EGP, and statically configured information) into the OSPF domain, enable AS boundary routing. You must do this even if the only route you want to import is the default route (destination 0.0.0.0).

When enabling AS boundary routing, you are asked which external routes you want to import. You can choose to import, or not to import, routes belonging to several categories. The categories are as follows:

RIP routes
EGP routes
Static routes
Direct routes

For example, you can choose to import EGP and direct routes, but not RIP or static routes. When you choose to import EGP routes, only the routes that appear in the EGP input exchange tables are actually imported. All routes are imported with cost equal to their routing table cost. They are all imported as either type 1 or type 2 external routes, depending on the routing protocol comparison (See next section).

Independently of the above external categories, you can also configure whether or not to import subnet routes into the OSPF domain. This configuration item defaults to OFF (subnets not imported).

The metric type used in importing routes determines how the imported cost is viewed by the OSPF domain. When comparing two type 2 metrics, only the external cost is considered in picking the best route. When comparing two type 1 metrics, the external and internal costs of the route are combined before making the comparison.

You are asked whether or not you want to originate an OSPF default route. You can answer always, never, or only if you have EGP routes. If originating a default route when EGP routes are available, you can also choose to originate the default only if EGP routes are received from a particular Autonomous System or if a particular route is received through the EGP.

Combinations of these options are possible. For example, you can set the router so that its default is originated only if a route to 10.0.0.0 is received from AS number 12. Setting the AS number to 0 means "from any AS." Setting the network number to 0.0.0.0 means "any routes received."

Use the enable as command as follows:

OSPF Config>enable as
Import EGP routes? [Yes]:
Import BGP routes? [Yes]:
		Automatically generate tags? [Yes]:
Import RIP routes? [Yes]:
Import static routes? [No]:
Import direct routes? [Yes]:
Import subnet routes? [No]:
Always originate default route? [Yes]: no
Originate default if EGP/BGP routes available? [No]: yes
	From AS number [0]? 12
	To network number [0.0.0.0]? 10.0.0.0
Originate as type 1 or 2 [2]?
Default route cost [1]?
Default forwarding address [0.0.0.0]?

Setting Non-Broadcast Network Parameters

If the router is connected to a non-broadcast, multi-access network, such as an X.25 PDN (Public Data Network), you have to configure the parameters below to help the router discover its OSPF neighbors. This configuration is only necessary if the router is eligible to become designated router of the non-broadcast network.

First configure the OSPF poll interval with the following command:

OSPF Config> set interface
Interface IP address [0.0.0.0]? 128.185.138.19
Attaches to area [0.0.0.0]?
.
.
.
Override the default OSPF interface-type? [No]: yes
OSPF interface-type override
Poll Interval [120]?

Then configure the IP addresses of all other OSPF routers that will be attached to the non-broadcast network. For each router configured, you must also specify its eligibility to become the designated router.

OSPF Config> add neighbor 
Interface IP address [0.0.0.0]? 128.185.138.19
IP Address of Neighbor [0.0.0.0]? 128.185.138.21
Can that router become Designated Router [Yes]?

Other Configuration Tasks

In addition to the required and optional tasks already described, you can carry out the tasks described in the following sections:

Setting OSPF Router IDs

Every router in an OSPF routing domain must have a 32-bit router ID. By default, the OSPF router ID is the address of the first OSPF interface appearing in the router's configuration.

You can also explicitly set the OSPF router ID using the IP config>set router id command. The router ID must still be one of the router's IP interface addresses.

Setting Virtual Links

To maintain backbone connectivity, you must have all of your backbone routers interconnected either by permanent or virtual links. You can configure virtual links between any two area border routers that share a common non-backbone and non-stub area. Virtual links are considered separate router interfaces connecting to the backbone area. Therefore, you are asked to also specify many of the interface parameters when configuring a virtual link.

You must configure virtual links in each of the link's two endpoints. Note that OSPF router IDs are entered in the same form as IP addresses.

OSPF Config>set virtual-link
Virtual endpoint (Router ID) [0.0.0.0]? 128.185.138.21
Link's transit area [0.0.0.1]?
Retransmission Interval (in seconds) [10]?
Transmission Delay (in seconds) [5]?
Hello Interval (in seconds) [30]?
Dead Router Interval (in seconds) [180]?
Authentication Key?
Message Digest Key ID [0]?
Message Digest Key?
Retype Message Digest Key?

Configuring for Routing Protocol Comparisons

If you use a routing protocol in addition to OSPF, or when you change your routing protocol to OSPF, you must set the Routing Protocol Comparison.

OSPF routing in an AS occurs on the following three levels: intra-area, inter-area, and exterior.

Intra-area routing occurs when a packet's source and destination address reside in the same area. For example, N1 and N2 in Area 1 (Figure 1). Information that is about other areas does not affect this type of routing.
Inter-area routing occurs when the packet's source and destination addresses reside in different areas of an AS, for example, N1 of Area 1 and N7 of Area 2 (Figure 1). OSPF does inter-area routing by dividing the path into three contiguous pieces: an intra-area path from source to an area border router; a backbone path between the source and destination areas; and then another intra-area path to the destination. You can visualize this high-level of routing as a star topology with the backbone as hub and each of the areas as a spoke.
Exterior routes are paths to networks that lie outside the AS. These routes originate either from routing protocols, such as Exterior Gateway Protocol (EGP) or from static routes. The exterior routing information that EGP provides does not interfere with the internal routing information that OSPF provides.

AS boundary routers may import exterior routes into the OSPF routing domain. OSPF represents these routes as AS external link advertisements.

OSPF imports external routes in separate levels. The first level, called type 1 routes, is used when the external metric is comparable to the OSPF metric (e.g., they might both use delay in milliseconds). The second level, called external type 2 routes, assumes that the external cost is greater than the cost of any internal OSPF (link-state) path.

Imported external routes are tagged with 32-bits of information. In a router, this 32-bit field indicates the AS number from where the route was received. This enables more intelligent EGP behavior when determining whether to re-advertise the external information to other ASs.

OSPF has a 4-level routing hierarchy as shown below. The set comparison command tells the router where the RIP/EGP/static routes fit in the OSPF hierarchy.

OSPF Config>set comparison
Compare to type 1 or 2 externals [2]?

The two lower levels consist of the OSPF internal routes. OSPF intra-area and inter-area routes take precedence over information obtained from any other sources, all of which are located on a single level.

Figure 2 OSPF Routing Hierarchy

To put the EGP/RIP/static routes on the same level as OSPF external type 1 routes, set the comparison to 1. To put the EGP/RIP/static routes on the same level as OSPF external type 2 routes, set the comparison to 2. The default is 2.

For example, if the comparison is set to 2, when RIP routes are imported into the OSPF domain, they are imported as type 2 externals. All OSPF external type 1 routes override received RIP routes, regardless of metric. However, if the RIP routes have a smaller cost, the RIP routes override OSPF external type 2 routes. The comparison values for all of your OSPF routers must match. If the comparison values set for the routers are inconsistent, your routing will not function properly.

OSPF Commands

Table 1 lists the OSPF commands.

Press Space twice after you type a command to display the available options for each command. Enter help for information about using the command line interface.

[C] means the command is available at the OSPF config> prompt.

[M] means the command is available at the OSPF> prompt.

Table 1 OSPF Commands

Command Function

Add [C] Adds to already existent OSPF information. You can add ranges to areas, and neighbors to non-broadcast networks.

Advertisement [M] Advertisement expansion. Displays a link state advertisement (LSA) belonging to the OSPF database.

Area [M] Area summary. Displays OSPF area statistics and parameters.

AS-external [M] AS-external advertisements. Lists the AS external advertisements belonging to the OSPF link state database.

Database [M] Database summary. Displays the advertisements belonging to an OSPF area's link state database.

Delete [C] Deletes OSPF information from the current OSPF configuration.

Disable [C] Disables the entire OSPF protocol, AS boundary routing capability, or IP multicast routing.

Dump [M] Dump routing tables. Displays the OSPF routes contained in the routing table.

Enable [C] Enables the entire OSPF protocol, AS boundary routing capability, IP multicast routing, or the subnet advertisement option.

Exit [C] [M] Returns to the previous prompt.

IGMP [C] [M] Displays the Internet Group Management Protocol (IGMP) configuration or monitoring prompt. IGMP detects the presence of multicast host receivers.

Interface [M] Interface summary. Displays OSPF interface statistics and parameters.

List [C] Displays OSPF configuration.

Mcache [M] Displays a list of currently active multicast forwarding cache entries.

Mstats [M] Displays various multicast routing statistics.

Neighbor [M] Neighbor summary. Displays OSPF neighbor statistics and parameters.

Ping [M] Ping address. Used to test for network reachability and fault isolation.

Routers [M] Displays the reachable OSPF area-border routers and AS-boundary routers.

Set [C] Establishes or changes the configuration of OSPF areas, interfaces, or virtual links. Also allows you to set the way in which OSPF routes are compared to information gained from other routing protocols.

Size [M] Displays the number of LSAs currently in the link state database, categorized by type.

Statistics [M] Displays OSPF statistics detailing memory and network usage.

Traceroute [M] Traceroute address. Displays the route taken to a host or network gateway

Weight [M] Dynamically changes the cost of an OSPF interface.

Table 1 OSPF Commands
Command	Function
Add [C]	Adds to already existent OSPF information. You can add ranges to areas, and neighbors to non-broadcast networks.
Advertisement [M]	Advertisement expansion. Displays a link state advertisement (LSA) belonging to the OSPF database.
Area [M]	Area summary. Displays OSPF area statistics and parameters.
AS-external [M]	AS-external advertisements. Lists the AS external advertisements belonging to the OSPF link state database.
Database [M]	Database summary. Displays the advertisements belonging to an OSPF area's link state database.
Delete [C]	Deletes OSPF information from the current OSPF configuration.
Disable [C]	Disables the entire OSPF protocol, AS boundary routing capability, or IP multicast routing.
Dump [M]	Dump routing tables. Displays the OSPF routes contained in the routing table.
Enable [C]	Enables the entire OSPF protocol, AS boundary routing capability, IP multicast routing, or the subnet advertisement option.
Exit [C] [M]	Returns to the previous prompt.
IGMP [C] [M]	Displays the Internet Group Management Protocol (IGMP) configuration or monitoring prompt. IGMP detects the presence of multicast host receivers.
Interface [M]	Interface summary. Displays OSPF interface statistics and parameters.
List [C]	Displays OSPF configuration.
Mcache [M]	Displays a list of currently active multicast forwarding cache entries.
Mstats [M]	Displays various multicast routing statistics.
Neighbor [M]	Neighbor summary. Displays OSPF neighbor statistics and parameters.
Ping [M]	Ping address. Used to test for network reachability and fault isolation.
Routers [M]	Displays the reachable OSPF area-border routers and AS-boundary routers.
Set [C]	Establishes or changes the configuration of OSPF areas, interfaces, or virtual links. Also allows you to set the way in which OSPF routes are compared to information gained from other routing protocols.
Size [M]	Displays the number of LSAs currently in the link state database, categorized by type.
Statistics [M]	Displays OSPF statistics detailing memory and network usage.
Traceroute [M]	Traceroute address. Displays the route taken to a host or network gateway
Weight [M]	Dynamically changes the cost of an OSPF interface.

Add [C]

Adds ranges to OSPF areas as well as neighbors to non-broadcast networks.

Syntax: add

range
neighbor

range area# IP-address IP-address-mask

Adds ranges to OSPF areas. OSPF areas are defined in terms of address ranges. External to the area, a single route is advertised for each address range. For example, if an OSPF area consists of all subnets of the class B network 128.185.0.0, you define it as consisting of a single address range. You would specify the address range as an address of 128.185.0.0 together with a mask of 255.255.0.0. Outside of the area, the entire subnetted network is advertised as a single route to network 128.185.0.0.

Example: add range

Area number [0.0.0.0]? 0.0.0.2
IP Address [0.0.0.0]? 128.185.0.0
IP Address Mask [0.0.0.0]? 255.255.0.0
Inhibit advertisement? [No]:

neighbor

Adds neighbors to non-broadcast networks. If the router is connected to a non-broadcast, multi-access network, such as Frame Relay, you have to use this command to help the router discover its OSPF neighbors. This configuration is only necessary if the router is eligible to become designated router of the non-broadcast network. Configure the IP addresses of all other OSPF routers that will be attached to the non-broadcast network. For each router configured, you must also specify its eligibility to become designated router.

Example: add neighbor

Interface IP address [0.0.0.0]? 128.185.138.19
IP Address of Neighbor [0.0.0.0]? 128.185.138.21
Can that router become Designated Router [Yes]?

Advertisement [M]

Displays the contents of a link state advertisement (LSA) contained in the OSPF database. For a summary of the router's advertisements use the database command.

A link state advertisement is defined by its link state type, link state ID and its advertising router. There is a separate link state database for each OSPF area. Providing an area-id on the command line tells the software which database you want to search.

Note: Link State IDs, advertising routers (specified by their router IDs), and area IDs take the same format as IP addresses. For example, you can enter the backbone area as 0.0.0.0.

The different kinds of advertisements, which depend on the value given for link-state-type, are

Router links—Contain descriptions of a single router's interface.
Network links—Contain the list of routers attached to a particular interface.
Summary nets—Contain descriptions of a single inter-area route.
Summary AS boundary routers—Contain descriptions of the route to an AS boundary router in another area.
AS external nets—Contain descriptions of a single route.
Multicast group memberships—Contain descriptions of a particular group's membership in the neighborhood of the advertising router.

The example below shows an expansion of a router links advertisement. The router's ID is 128.185.184.11. It is an AS boundary router and has three interfaces to the backbone area (all of cost 1). Multicast routing is enabled. Detailed field descriptions are provided with the example shown below.

When displaying router-LSAs and network-LSAs, the reverse cost of each router-to-router link and router-to-transit-network link is displayed, as well as the previously displayed forward cost. This is done because routing of multicast datagrams whose source lies in different areas/ASs is based on reverse cost instead of forward cost. In cases where there is no reverse link (which means that the Dijkstra will never use the link), the reverse cost is shown as "1-way."

The "LS destination" of each group-membership-LSA is a group address. A router originates a group-membership-LSA for each group with members on one or more of the router's attached networks. The group-membership-LSA for the group lists the attached transit networks having type "2" vertices and when there are members belonging to one or more attached stub networks, or if the router itself is a member of the multicast group, a type "1" vertex.

Syntax: advertisement

ls-type link-state-id advertising router area id

Example: advertisement

Link state type [1]?
Link state ID (destination) [0.0.0.0]? 10.1.2.7
For which area [0.0.0.0]? 2.2.2.2
        LS age:     437
        LS options: E,MC
        LS type:     1
        LS destination (ID): 10.1.2.7
        LS originator:   10.1.2.7
        LS sequence no: 0x80000025
        LS checksum:     0xB13C
        LS length:       72
        Router type: 
        # router ifcs:   4
                Link ID:          10.1.50.16
                Link Data:        10.1.2.7
                Interface type:   1
                        No. of metrics: 0
                        TOS 0 metric:   1 (1)
                Link ID:          10.1.22.0
                Link Data:        255.255.255.0
                Interface type:   3
                        No. of metrics: 0
                        TOS 0 metric:   1 
                Link ID:          10.1.2.16
                Link Data:        255.255.255.255
                Interface type:   3
                        No. of metrics: 0
                        TOS 0 metric:   1 
                Link ID:          10.1.50.7
                Link Data:        255.255.255.255
                Interface type:   3
                        No. of metrics: 0
                        TOS 0 metric:   0


LS age	Age of the advertisement in seconds.
LS options	Optional OSPF capabilities supported by the piece of the routing domain described by the advertisement. These capabilities are denoted by E (processes type 5 externals; when this is not set to the area to which the advertisement belongs has been configured as a stub), T (can route based on TOS) and MC (can forward IP multicast datagrams).
LS type	Classifies the advertisement and dictates its contents: 1 (router links advertisement), 2 (network link advertisement), 3 (summary link advertisement), 4 (summary ASBR advertisement), 5 (AS external link) and 6 (group-membership advertisement).
LS destination	Identifies what is being described by the advertisement. Depends on the advertisement type. For router links and ASBR summaries, it is the OSPF router ID. For network links, it is the IP address of the network's designated router. For summary links and AS external links, it is a network/subnet number. For group-membership advertisements, it is a particular multicast group.
LS originator	OSPF router ID of the originating router.
LS sequence number	Used to distinguish separate instances of the same advertisement. Should be looked at as a signed 32-bit integer. Starts at 0x80000001, and increments by one each time the advertisement is updated.
LS checksum	A checksum of advertisement contents, used to detect data corruption.
LS length	The size of the advertisement in bytes.
Router type	Level of functionality of the router. ASBR means that the router is an AS boundary router, ABR that the router is an area border router, and W that the router is a wildcard multicast receiver.
# Router ifcs	The router interface that the advertisement describes.
Link ID	Indicates what the interface connects to. Depends on Interface type. For interfaces to routers (point-to-point links), the Link ID is the neighbor's router ID. For interfaces to transit networks, it is the IP address of the network. Designated router. For interfaces to stub networks, it is the network's network/subnet number.
Link Data	4 bytes of extra information concerning the link, it is either the IP address of the interface (for interfaces to point-to-point networks and transit networks), or the subnet mask (for interfaces to stub networks).
Interface type	One of the following: 1 (point-to-point connection to another router, 2 (connection to transit network, 3 (connection to stub network) or 4 (virtual link).
No. of metrics	The number of non-zero TOS values for which metrics are provided for this interface.
TOS 0 metric	The cost of the interface. In parenthesis the reverse cost of the link is given (derived from another advertisement). If there is no reverse link, "1-way" is displayed.

The LS age, LS options, LS type, LS destination, LS originator, LS sequence no, LS checksum and LS length fields are common to all advertisements. The Router type and # router ifcs are seen only in router links advertisements. Each link in the router advertisement is described by the Link ID, Link Data, and Interface type fields. Each link can also be assigned a separate cost for each IP Type of Service (TOS); this is described by the No. of metrics and TOS 0 metric fields (the router currently does not router based on TOS, and looks at the TOS 0 cost only).

The next example shows an expansion of a group-membership advertisement. A group-membership advertisement for a given group/advertising router combination lists those networks directly attached to the advertising router which have group members. It also lists whether the router itself is a member of the specified group. The example below shows that network 128.185.184.0 has members of group 224.0.1.1.

Example: adv 6 224.0.1.1 128.185.184.114

For which area [0.0.0.0]?

              LS age:     168
              LS options: E
              LS type:     6
              LS destination (ID): 224.0.1.1
              LS originator:   128.185.184.114
              LS sequence no: 0x80000001
              LS checksum:     0x7A3
              LS length:       28
              Vertex type: 2
              Vertex ID:   128.185.184.114


Vertex type	Describes the object having group members, one of: 1 (the router itself, or stub networks attached to the router) or 2 (a transit network).
Vertex ID	When the vertex type is 1, always the advertising router's ID. When the vertex type is 2, the IP address of the transit network's designated router.

Area [M]

Displays the statistics and parameters for all OSPF areas attached to the router.

In the example below, the router attaches to a single area (the backbone area) and uses a simple password scheme for the area's authentication. The router has three interfaces attaching to the area, and has found 4 transit networks, 7 routers and no area border routers when calculating the SPF tree for the backbone.

Syntax: area summary

Example: area summary

Area ID          Authentication   #ifcs #nets #rtrs #brdrs
2.2.2.2           None              1      2      5      3
0.0.0.0           None              1      0      2      2
5.5.5.5           None              1      1      3      1


# ifcs	Router interfaces attached to the particular area. These interfaces are not necessarily functional.
# nets	Transit networks found while doing the SPF tree calculation for this area.
# rtrs	Routers found when doing the SPF tree calculation for this area.
# brdrs	Area border routers found when doing the SPF tree calculation for this area.

AS-external [M]

Lists the AS external advertisements that belong to the OSPF link state database. Each advertisement is defined by the following parameters: its link state type (always 5 for AS external advertisements), its link state ID (called the LS destination), and the advertising router (called the LS originator).

Syntax: as-external

Example: as-external

Type LS destination LS originator Seqno      Age   Xsum
 5 0.0.0.0       128.185.123.22 0x80000084 430   0x41C7
 5 128.185.131.0 128.185.123.22 0x80000080 450 0x71DC
 5 128.185.132.0 128.185.123.22 0x80000080 450 0x66E6
 5 128.185.144.0 128.185.123.22 0x80000002 329 0xF2CA
 5 128.185.178.0 128.185.123.22 0x80000081 450 0x72AA
 5 128.185.178.0 128.185.129.40 0x80000080 382 0xDD28
 5 129.9.0.0     128.185.123.22 0x80000082 451 0x4F30
 5 129.9.0.0     128.185.126.24 0x80000080 676 0x324A
 5 134.216.0.0   128.185.123.22 0x80000082 451 0x505A
 5 134.216.0.0   128.185.126.24 0x80000080 676 0x3374
 5 192.9.3.0     128.185.123.22 0x80000082 451 0xF745
 5 192.9.3.0     128.185.126.24 0x80000080 677 0xDA5F
 5 192.9.12.0    128.185.123.22 0x80000082 452 0x949F
 5 192.9.12.0    128.185.128.41 0x80000080 679 0x31B2
 5 192.26.100.0 128.185.123.22 0x80000081 452 0xFDCD
 5 192.26.100.0 128.185.126.24 0x80000080 21 0xDEE8
                             etc.
                      # advertisements: 133
                      Checksum total: 0x43CC41


Type	Always 5 for AS external advertisements.
LS destination	IP network/subnet number. These network numbers belong to other Autonomous Systems.
LS originator	Advertising router.
Seqno, Age, Xsum	Several instances of an advertisement can be present in the OSPF routing domain. However, only the most recent instance is kept in the OSPF link state database (and shown by this command). The LS sequence number (Seqno), LS age (Age) and LS checksum (Xsum) are compared to see which instance is most recent. The LS age is expressed in seconds. Its maximum value is 3600.

The end of the display shows the total number of AS external advertisements, along with a checksum total over all of their contents. The checksum total is simply the 32-bit sum (carries discarded) of the individual advertisement's LS checksum fields. You can use this information to quickly determine whether two OSPF routers have synchronized databases.

Database [M]

Displays the contents of a particular OSPF area's link state database. AS external advertisements are omitted from the display. Each advertisement is defined by the following parameters: link state type (called Type), link state ID (called the LS destination) and the advertising router (called the LS originator).

Syntax: database summary area-id

Example: database

For which area [0.0.0.0]? 0.0.0.0 
Type LS destination     LS originator     Seqno     Age   Xsum
1*   10.1.2.7           10.1.2.7        0x80000025 390 0xB13C    
1*   10.1.26.9          10.1.26.9       0x80000016 393 0x987D    
1*   10.1.26.41         10.1.26.41      0x80000018 122 0x533D    
1*   10.1.40.40         10.1.40.40      0x80000015 192 0x317C    
1*   10.1.50.16         10.1.50.16      0x80000031 394 0x7A74    
2*   10.1.25.40         10.1.40.40      0x80000006 193 0xCB35    
2*   10.1.26.16         10.1.50.16      0x80000007 401 0x9669    
3*   10.2.50.9          10.1.26.9       0x80000010 397 0xA430    
3*   10.5.0.0           10.1.26.41      0x8000000F 133 0x4E9E    
3*   10.5.50.41         10.1.26.9       0x80000006 394 0x5D5D    
3*   128.185.214.0      10.1.40.40      0x8000000E 740 0x3CA2    
6    224.185.0.0        10.1.50.16      0x8000000F 469 0x9B7A    
6    225.0.1.36         10.1.2.7        0x80000006 405 0x5CC8    
6    225.0.1.36         10.1.26.9       0x8000000F 404 0x8265    
6    225.0.1.36         10.1.26.41      0x8000000F 133 0x3A4    
6    225.0.1.36         10.1.40.40      0x8000000E 755 0x1D71    
6    225.0.1.100        10.1.50.16      0x80000006 476 0x5E14    
                # advertisements:       17
                Checksum total:         0x73121


Type	Displays LS types: type 1 (router links advertisements), type 2 (network links advertisements), type 3 (network summaries), type 4 (AS boundary router summaries), and type 6 (group-membership-LSAs).
LS destination	Indicates what is being described by the advertisement.
LS originator	Advertising router.
Seqno, Age, Xsum	It is possible for several instances of an advertisement to be present the OSPF routing domain. However, only the most recent instance is kept in the OSPF link state database (and shown by this command). The LS sequence number (Seqno), LS age (Age) and LS checksum (Xsum) are compared to see which instance is most recent. The LS age field is expressed in seconds. Its maximum value is 3600.

The end of the display shows the total number of advertisements in the area databas, along with a checksum total over all of their contents. The checksum total is simply the 32-bit sum (carries discarded) of the individual advertisement's LS checksum fields. You can use this information to quickly determine whether two OSPF routers have synchronized databases.

Note: When comparing multicast-capable to non-multicast routers, the above database checksum (and also # advertisements) does not necessarily match because non-multicast routers do not handle or store group-membership-LSAs.

Delete [C]

Deletes OSPF information from the router's current OSPF configuration.

Syntax: delete

range
area
interface
neighbor
virtual-link

range area# IP-address

Deletes ranges from OSPF areas.

Example: delete range

Area number [0.0.0.0]? 1.1.1.1
IP Address [0.0.0.0]? 128.185.0.0
IP Address Mask [0.0.0.0]? 255.255.0.0

Interface IP address [0.0.0.0]? 128.185.138.19
IP Address of Neighbor [0.0.0.0]? 128.185.138.21

virtual-link

Deletes a virtual link. You can configure virtual links between any two backbone routers that have an interface to a common non-backbone area. Virtual links maintain backbone connectivity and must be configured at both endpoints.

Example: delete virtual-link

Virtual endpoint (Router ID) [0.0.0.0]? 
Link's transit area [0.0.0.1]?

Disable [C]

Disables either the entire OSPF protocol or just the AS boundary routing capability, IP multicast routing, or the subnet advertisement option.

Syntax: disable

as
multicast
ospf
subnet

as

Disables the AS boundary routing capability. When disabled, the router does not import external information into the OSPF domain.

Example: disable as boundary routing

multicast

Disables IP multicast routing on all interfaces. When disabled, the router does not forward IP multicast (Class D) datagrams.

Example: disable multicast forwarding

ospf

Disables the entire OSPF protocol.

Example: disable OSPF routing protocol

subnet

Disables the subnet advertisement option on a selected interface.

Example: disable subnet

Interface IP address [0.0.0.0]?

Dump [M]

Displays the routes that have been calculated by OSPF and are now present in the routing table. Its output is similar to the IP monitoring dump routing tables command.

Syntax: dump

Example: dump

Type   Dest net         Mask     Cost Age Next hop(s)    

Sbnt   10.0.0.0         FF000000  1    0    None            
Rnge   10.1.0.0         FFFF0000  1    0    None            
 SPF   10.1.2.7         FFFFFFFF  2    2    10.1.26.16      
 SPF   10.1.2.16        FFFFFFFF  3    3    10.1.26.16      
 SPF   10.1.7.16        FFFFFFFF  3    3    10.1.26.16      
 SPF   10.1.7.40        FFFFFFFF  2    2    10.1.26.16      
 SPF   10.1.22.0        FFFFFF00  3    3    10.1.26.16      
 SPF   10.1.25.0        FFFFFF00  2    2    10.1.26.16      
 SPF*  10.1.26.0        FFFFFF00  1    1    FDDI/0          
 SPF   10.1.40.40       FFFFFFFF  2    2    10.1.26.16      
 SPF   10.1.50.7        FFFFFFFF  2    2    10.1.26.16      
 SPF   10.1.50.16       FFFFFFFF  1    1    10.1.26.16      
 SPF   10.2.50.9        FFFFFFFF  1    1    10.1.26.9       
Rnge   10.5.0.0         FFFF0000  1    0    None            
 Dir*  10.5.9.0         FFFFFF00  1    0    SL/0            
 SPF   10.5.9.14        FFFFFFFF  1    1    10.5.9.14       
 SPF   10.5.9.41        FFFFFFFF  2    2    SL/0            
 SPF   10.5.22.0        FFFFFF00  8    8    10.5.9.14       
 SPF   10.5.33.0        FFFFFF00  2    2    10.5.9.14       
 SPF   10.5.50.14       FFFFFFFF  1    1    10.5.9.14       
 SPF   10.5.50.41       FFFFFFFF  0    0    SINK/0          
 Stat* 128.185.0.0      FFFF0000  1    0    10.1.26.16      

Routing table size: 768 nets (49152 bytes), 22 nets known


Type	Route type and how the route was derived: SPF—indicates an OSPF internal route. This is a real, pure OSPF route derived from OSPF routers talking to each other. Each OSPF router talks about the IP networks that are immediately adjacent to itself that it knows about and relays this information to all the other OSPF routers within the same area. The total sum of this information is the real OSPF database. SPF—The `' means that there is or has been in the past a STATIC route defined for this same route (network/mask combination), but this static route is not being used now since the current route is of higher priority. Rnge—indicates an active area address range which is not used in forwarding packets. SPE1 and SPE2—indicate OSPF external routes type 1 and 2, respectively. Not pure OSPF-derived routes. OSPF has learned about this routing information from a source other than OSPF itself. As one example, a STATIC route is defined on an AS boundary router and told to import the STATIC route into the OSPF database. When this ASBR route advertises this route it is marked as an SPE1 or SPE2 route to say that the routing information did not come from OSPF. Sbnt—subnetted network. Only display if RIP is running on the router. You can ignore these (unless you are running RIP). These are artificially created entries on the natural Class boundary whose only purpose is to assist RIPv1 in generating its routing packets. (RIPv1 is the oldest of IP protocols and is limited to advertising routes only on IP class boundaries). RIP—a route learned from the Routing Information Protocol (RIP) rather than from OSPF. Dir— Stat—
Destination	Destination host or network.
Mask	Entry's subnet mask.
Cost	Route cost.
Age	This field is applicable when running RIP. For OSPF routes, this field equals the cost of the route.
Next hop	Address of the next router on the path toward the destination host. A number in parentheses at the end of the column indicates the number of equal-cost routes to the destination. You can display the first hops belonging to these routes with the IP monitoring route command.

Enable [C]

Enables either the entire OSPF protocol or just the AS boundary routing capability, IP multicast routing, or the subnet advertisement option.

Syntax: enable

as
multicast
ospf
subnet

as

Enables the AS boundary routing capability that allows you to import routes learned from other protocols (EGP, RIP, and statically configured information) into the OSPF domain.

Example: enable as

Import EGP routes(Yes or No): yes
Import RIP routes(Yes or No): no
Import static routes(Yes or No): no
Import direct routes(Yes or No): yes
Import subnet routes(Yes or No): no
Originate default if EGP routes available []? yes
   From AS number [0]? 12
   To network number [0.0.0.0]? 10.0.0.0
Originate as type 1 or 2 [2]? 
Default route cost [1]?

multicast

Enables the forwarding of IP multicast (Class D) datagrams. This command also lets you enable IP multicast forwarding between OSPF areas and between Autonomous Systems. To run MOSPF (OSPF with multicast extensions), a router currently running OSPF needs to use only this command. You do not need to re-enter its configuration information.

Example: enable multicast

Inter-area multicasting enabled (Yes or No): yes
Inter-AS multicasting enabled (Yes or No): yes

If you enabled multicast routing, the MOSPF parameters for each OSPF interface are set to their default values. This means the following:

Multicast forwarding is enabled.
Multicast datagrams are forwarded as data-link multicasts.

To change the MOSPF parameters, use the set interface command. You will be queried for multicast parameters (the last two parameters shown in the output display above) only if you have first enabled multicast forwarding.

On networks that lie on the edge of an Autonomous System, where multiple multicast routing protocols (or multiple instances of a single multicast routing protocol) may exist, you may need to configure forwarding as data-link unicasts to avoid unwanted datagram replication. In any case, for all routers attached to a common network, the interface parameters forward multicast datagrams and forward as data-link unicasts should be configured identically.

ospf

Enables the OSPF protocol. When enabling OSPF, you must supply the following values that are used to estimate the size of the OSPF link state database:

Total number of AS external routes that will be imported into the OSPF routing domain.

A single destination may lead to multiple external routes when separate AS boundary routers import the destination. For example, if the OSPF routing domain has two AS boundary routers, both importing routes to the same 100 destinations, set the number of AS external routes to 200.
Total number of OSPF routers in the routing domain.

Example: enable ospf

Estimated # external routes[0]? 200
Estimated # OSPF routers [0]? 60

subnet

Enables subnet advertisement option. This option allows the router to advertise the addresses of the hosts on the subnet.

Example: enable subnet

Interface IP address [0.0.0.0]?

Exit [C] [M]

Returns to the previous prompt.

Syntax: exit

IGMP [C] [M]

Displays the Internet Group Management Protocol (IGMP) configuration or monitoring prompt. See IGMP Commands for information on the commands available at these prompts.

Syntax: igmp

Example: igmp

Internet Group Management Protocol Configuration

IGMP Config>

Interface [M]

Displays statistics and parameters related to OSPF interfaces. If you do not specify a particular interface, a single line summarizing each interface is displayed for each interface on the router. If you enter an interface's IP address, detailed statistics for that interface are displayed.

Syntax: interface interface-ip-address

Example: interface

Ifc Address      Phys    assoc. Area      Type   State   #nbrs  #adjs
10.1.26.41       FDDI/0  2.2.2.2         Brdcst   32        2        2
10.5.9.41        SL/0    5.5.5.5         P-P       8        2        1
- Unnumbered -   VL/0    0.0.0.0         VLink     8        1        1


Ifc Address	Interface IP address.
Phys	Medium for the physical interface.
Assoc Area	Attached area ID.
Type	Brdcst (broadcast, such as an Ethernet interface) P-P (point-to-point, such as a serial line) Multi (non-broadcast, multi-access, such as Frame Relay) VLink (an OSPF virtual link)
State	Can be one of the following: 1 (down), 2 (looped back), 4 (waiting), 8 (point-to-point), 16 (DR other), 32 (backup DR) or 64 (designated router).
#nbrs	Number of neighbors. This is the number of routers whose hellos have been received, plus those that have been configured.
#adjs	Number of adjacencies. This is the number of neighbors in state Exchange or greater. These are the neighbors with whom the router has synchronized or is in the process of synchronization.

Example: interface 128.185.125.22

Interface address:      10.1.26.41
          Attached area:          2.2.2.2
          Physical interface:     FDDI/0
          Interface mask:         255.255.255.0
          Interface type:         Brdcst
          State:                  32
          Designated Router:      10.1.26.16
          Backup DR:              10.1.26.41

 DR Priority:       1 Hello interval:   10 Rxmt interval:     5
 Dead interval:    40 TX delay:          1 Poll interval:     0
 Max pkt size:   4352 TOS 0 cost:        1
 # Neighbors:       2 # Adjacencies:     2 # Full adjs.:      2
 # Mcast floods:   31 # Mcast acks:     98

 MC forwarding:    on DL unicast:      off IGMP monitor:     on
 # MC data in:      0 # MC data acc:     0 # MC data out:     0


Attached Area	Attached area ID.
Physical interface	Displays physical interface type and number.
Interface Mask	Interface subnet mask.
Interface type	Brdcst (broadcast, such as an Ethernet interface) P-P (point-to-point, such as a serial line) Multi (non-broadcast, multi-access, such as Frame Relay) VLink (an OSPF virtual link)
State	Can be one of the following: 1 (Down), 2 (Attempt), 4 (Init), 8 (2-Way), 16 (ExStart), 32 (Exchange), 64 (Loading) or 128 (Full).
Designated Router	IP address of the designated router.
Backup DR	IP address of the backup designated router.
DR Priority	Priority assigned to designated router.
Hello interval	Current hello interval value.
Rxmt interval	Current retransmission interval value.
Dead interval	Current dead interval value.
TX delay	Current transmission delay value.
Poll interval	Current poll interval value.
Max pkt size	Maximum size for an OSPF packet sent out this interface.
TOS 0 cost	Interface's TOS 0 cost.
# Neighbors	Routers whose hellos have been received, plus those that have been configured.
# Adjacencies	Neighbors in state Exchange or greater.
# Full adj	Full adjacencies is the number of neighbors whose state is Full (and therefore, with which the router has synchronized databases).
# Mcast Floods	Link state updates flooded out the interface (not counting retransmissions).
# Mcast acks	Link state acknowledgements flooded out the interface (not counting retransmissions).
MC forwarding	Displays whether multicast is enabled for the interface.
DL unicast	Displays whether to forward multicast datagrams as data-link multicasts or as data-link unicasts.
IGMP monitor	Displays whether IGMP is enabled on the interface.
# MC data in	Multicast datagrams received on this interface and then successfully forwarded.
# MC data acc	Multicast datagrams successfully forwarded.
# MC data out	Datagrams sent out the interface (either as data-link multicasts or data-link unicasts).

List [C]

Displays OSPF configuration information.

Syntax: list

all
areas
interfaces
neighbors
virtual-link

all

Lists all OSPF related configuration information.

Example: list all

            --Global configuration--
                OSPF Protocol:          Enabled
                # AS ext. routes:       5000
                Estimated # routers:    50
                External comparison:    Type 2
                AS boundary capability: Disabled
                Multicast forwarding:   Enabled
                Inter-area multicast:   Enabled
                Inter-AS multicast:     Disabled

                        --Area configuration--
Area ID          AuType          Stub? Default-cost Import-summaries?
2.2.2.2          0=None           No         N/A           N/A
0.0.0.0          0=None           No         N/A           N/A
5.5.5.5          0=None           Yes        0             Yes

                        --Area ranges--
Area ID          Address          Mask             Advertise?
2.2.2.2          10.1.0.0         255.255.0.0      Yes
5.5.5.5          10.5.0.0         255.255.0.0      Yes

                        --Interface configuration--
IP address       Area            Cost  Rtrns  TrnsDly  Pri  Hello  Dead
10.1.26.41       2.2.2.2           1      5       1     1     10    40
10.5.9.41        5.5.5.5           1      5       1     1     10    40

                            Multicast parameters
IP address        MCForward       DLUnicast 
10.1.26.41        On              Off        
10.5.9.41         On              Off       

                        --Virtual link configuration--
Virtual endpoint     Transit area      Rtrns  TrnsDly Hello  Dead
10.1.26.9            2.2.2.2              10      5     30   180

                        --NBMA configuration--
                Interface Addr      Poll Interval 
                10.5.9.41           120

                        --Neighbor configuration--
                Neighbor Addr     Interface Address   DR eligible?
                10.5.9.14         10.5.9.41           yes


OSPF protocol	Displays whether OSPF is enabled or disabled.
# AS ext. routes	Estimated number of Autonomous System external routes. The router cannot accept more than this number of AS external routes.
Estimated # routers	Estimated number of routers found in the OSPF configuration.
External comparison	External route type OSPF uses when importing external information into the OSPF domain and when comparing OSPF external routes to RIP/EGP routes.
AS boundary capability	Displays whether the router imports external routes into the OSPF domain.
Import external	Displays which routes the router will import.
Orig default route	Displays whether the router imports a default route into the OSPF domain. When Yes, a non-zero network number is displayed in parentheses. This indicates that the default route will originate if and only if a route to that network is available.
Default route cost	Cost and type used in the imported default route.
Default forward addr	Forwarding address used in the imported default route.
Multicast forwarding	Displays whether the router forwards IP multicast datagrams.
Inter-area multicast	Displays whether the router forwards IP multicast datagrams between areas.
Inter-AS multicast	Displays whether the router forwards IP multicast between Autonomous Systems.
Area-ID	Attached area ID (area summary information)
Authentication	Method used for area authentication. Simple-pass means a simple password scheme is being used for the area's authentication.
Stub area	Displays whether or not the area being summarized is a stub area. Stub areas do not carry external routes, resulting in a smaller routing database. However, stub areas cannot contain AS boundary routers, nor can they support configured virtual links.
OSPF interfaces	For each interface, displays its IP address, together with configured parameters. Area— OSPF area to which the interface attaches. Cost— TOS 0 cost (or metric) associated with the interface. Rtrns— Retransmission interval, which is the number of seconds between retransmissions of unacknowledged routing information. TrnsDly— Transmission delay, which is an estimate of the number of seconds it takes to send routing information over the interface (it must be greater than 0). Pri— Interface's Router Priority, which is used when selecting the designated router. Hello— Seconds between Hello Packets sent out the interface. Dead— Seconds after Hellos cease to be heard that the router is declared down.
Virtual-link	Lists all virtual links that are configured with this router as endpoint. Virtual endpoint— the OSPF Router ID of the other endpoint. Transit area— the non-backbone area through which the virtual link is configured. OSPF treats virtual links similarly to point-to-point networks.

areas

Lists all information concerning configured OSPF areas.

Example: list areas

               --Area configuration--
Area ID        Stub?  Default-cost  Import-summaries?
1.1.1.1        Yes    0             Yes


Area-ID	Attached area ID (area summary information).
Stub area	Displays whether or not the area being summarized is a stub area.

interfaces

For each interface its IP address is printed, together with configured parameters.

Example: list interfaces

                  --Interface configuration--
IP address        Area         Cost  Rtrns  TrnsDly  Pri  Hello  Dead
162.6.0.34        1.1.1.1      1     5      1        1    10     40
128.185.5.2       0.0.0.0      1     5      1        1    10     40
128.185.5.9       0.0.0.0      1     5      1        1    10     40

IP address        AuType    MDId  SbntOpt  IfcType  NBMAPoll
162.6.0.34        0=None    0     Off      Deflt    120
128.185.5.2       2=Crypto  4     Off      Deflt    120
128.185.5.9       2=Crypto  4     Off      P-2-MP   120

                     Multicast parameters
IP address        MCForward         DLUnicast
162.6.0.34        On                Off
128.185.5.2       On                Off
128.185.5.9       On                Off

Note: If multicast is disabled, software does not display multicast parameters.


Area	OSPF area to which the interface attaches.
Cost	TOS 0 cost (or metric) associated with the interface.
Rtrns	Retransmission interval, which is the number of seconds between retransmissions of unacknowledged routing information.
TrnsDly	Transmission delay, which is an estimate of the number of seconds it takes to transmit routing information over the interface (it must be greater than 0).
Pri	Interface's router priority, which is used when selecting the designated router.
Hello	Number of seconds between Hello Packets sent out the interface.
Dead	Number of seconds after Hellos cease to be heard that the router is declared down.
AuType	Method used for area authentication:
MDId
SbntOpt
IfcType
NBMAPoll
MCForward
DLUnicast

neighbors

Lists all information related to interfaces connected to non-broadcast networks. For each non-broadcast interface, as long as the router is eligible to become designated router on the attached network, the polling interval is displayed together with a list of the router's neighbors on the non-broadcast network.

Example: list neighbors

Interface Addr      Poll Interval 
128.185.235.34       120

virtual-link

Lists all virtual links that have been configured with this router as endpoint. "Virtual endpoint" indicates the OSPF router ID of the other endpoint. "Transit area" indicates the non-backbone area through which the virtual link is configured. OSPF treats virtual links similarly to point-to-point networks. The other parameters listed (Rtrns, TrnsDly, Hello, and Dead) are maintained for all interfaces. See the OSPF list interfaces command for more information.

Example: list virtual-link

                        --Virtual link configuration--
Virtual endpoint     Transit area      Rtrns TrnsDly Hello Dead
10.1.26.9             2.2.2.2            10      5     30     180

Mcache [M]

Displays a list of currently active multicast cache entries. Multicast cache entries are built on demand, whenever the first matching multicast datagram is received. There is a separate cache entry (and therefore a separate route) for each datagram source network and destination group combination.

Cache entries are cleared on topology changes (e.g., a point-to-point line in the MOSPF system going up or down), and on group membership changes.

Syntax: mcache

Example: mcache

 0: FDDI/0          1: SL/0            2: SL/1            
 3: SL/2            4: SL/3            5: Eth/0           
 6: Eth/1           7: Eth/2           8: Eth/3           
 9: Eth/4           10: Eth/5          11: Eth/6           
 12: Eth/7          13: Internal        

 Source          Destination     Count   Upst    Downstream
 10.5.50.41      225.0.1.100     3       Local   0
 10.5.50.14      225.0.1.100     3       1       0
 10.2.50.9       225.0.1.100     3       0       None
 10.1.50.7       225.0.1.100     3       0       None
 10.1.50.16      225.0.1.36      3       0       1,13


Source	Source network/subnet of matching datagrams.
Destination	Destination group of matching datagrams.
Upstream	Neighboring network/router from which the datagram must be received in order to be forwarded. None means the datagram is never forwarded.
Down	Downstream interfaces/neighbors to which the datagram will be forwarded. Zero (0) means the datagram is not forwarded.
Usage	Received datagrams that matched the cache entry.

There is more information in a multicast forwarding cache entry. You can display a cache entry in detail by providing the source and destination of a matching datagram on the command line. If a matching cache entry is not found, one is built. A sample of this command follows:

Example: mcache 128.185.182.9 224.0.1.2

source Net:     128.185.182.0
Destination:    224.0.1.2
Use Count:      472
Upstream Type: Transit Net
Upstream ID:    128.185.184.114
Downstream:     128.185.177.11 (TTL = 2)

In addition to the information shown in the short form of the mcache command, the following fields are displayed:


Upstream Type	Type of node from which the datagram must be received in order to be forwarded. Possible values for this field are none (the datagram will not be forwarded), router (the datagram must be received over a point-to-point connection), transit network, stub network, and external (the datagram is expected to be received from another Autonomous System).
Down- stream	Prints a separate line for each interface or neighbor to which the datagram will be sent. A TTL value is also given, indicating that datagrams forwarded out of or to this interface must have at least the specified TTL value in their IP header. When the router is itself a member of the multicast group, a line specifying "internal Application" appears as one of the downstream interfaces/neighbors.

Mstats [M]

Displays various multicast routing statistics. The command indicates whether multicast routing is enabled and whether the router is an inter-area and/or inter-AS multicast forwarder.

Syntax: mstats

Example: mstats

             MOSPF forwarding:       Enabled
             Inter-area forwarding: Enabled
             DVMRP forwarding:       Disabled

Datagrams received:            4301 Datagrams (ext source):          0
Datagrams fwd (multicast):     4122 Datagrams fwd (unicast):         0
Locally delivered:             2009 No matching rcv interface:       0
Unreachable source:               0  Unallocated cache entries:       0
Off multicast tree:               0  Unexpected DL multicast:         0
Buffer alloc failure:             0  TTL scoping:                     0

# DVMRP routing entries:          0  # DVMRP entries freed:           0
# fwd cache alloc:               57  # fwd cache freed:               52
# fwd cache GC:                   0  # local group DB alloc:          1
# local group DB free:            0


Multicast forwarding	Displays whether the router forwards IP multicast datagrams.
Inter-area multicast	Displays whether the router forwards IP multicast datagrams between areas.
DVMRP forwarding	Displays whether the router forwards IP multicast datagrams between Autonomous Systems.
Datagrams received	Multicast datagrams the router received. Does not include datagrams whose destination group is in the range 224.0.0.1 to 224.0.0.255.
Datagrams (ext source)	Datagrams received whose source is outside the AS.
Datagrams fwd (multicast)	Datagrams forwarded as data-link multicasts (this includes packet replications, when necessary, so this count could be greater than the number received).
Datagrams fwd (unicast)	Datagrams forwarded as data-link unicasts.
Locally delivered	Datagrams forwarded to internal applications.
No matching rcv interface	Datagrams received by a non-inter-AS multicast forwarder on a non-MOSPF interface.
Unreachable source	Datagrams whose source address was unreachable.
Unallocated cache entries	Datagrams whose cache entries could not be created due to resource shortages.
Off multicast tree	Datagrams not forwarded either because there was no upstream neighbor or no downstream interfaces/neighbors in the matching cache entry.
Unexpected DL multicast	Datagrams received as data-link multicasts on those interfaces that have been configured for data-link unicast.
Buffer alloc failure	Datagrams that could not be replicated because of buffer shortages.
TTL scoping	Datagrams that were not forwarded because their TTL indicated that they could never reach a group member.
# fwd cache alloc	Cache entries allocated. The current forwarding cache size is the number of entries allocated (# fwd cache alloc) minus the number of cache entries freed (# fwd cache freed).
# fwd cache freed	Cache entries freed. The current forwarding cache size is the number of entries allocated (# fwd cache alloc) minus the number of cache entries freed (# fwd cache freed).
# fwd cache GC	Cache entries were cleared because they were not recently used and the cache overflowed.
# local group DB alloc	Local group database entires allocated. The number allocated (# local group DB alloc) minus the number freed (# local group DB free) equals the current size of the local group database.
# local group DB free	Local group database entires freed. The number allocated (# local group DB alloc) minus the number freed (# local group DB free) equals the current size of the local group database.

The number of cache hits can be calculated as the number of datagrams received (Datagrams received) minus the total of datagrams discarded due to No matching rcv interface, Unreachable source and Unallocated cache entries, and minus # local group DB alloc." The number of cache misses is simply # local group DB alloc.

Neighbor [M]

Displays statistics and parameters related to OSPF neighbors. If you include a neighbor's IP address, this command displays detailed statistics for that neighbor.

Syntax: neighbor summary neighbor-ip-address

Example: neighbor

Neighbor addr   Neighbor ID     State LSrxl  DBsum  LSreq  Ifc
128.185.125.39  128.185.136.39  128      0     0       0    Pro/1 
128.185.125.41  128.185.128.41    8      0     0       0    Pro/1
128.185.125.38  128.185.125.38    8      0     0       0    Pro/1
128.185.125.25  128.185.129.25    8      0     0       0    Pro/1
128.185.125.40  128.185.129.40  128      0     0       0    Pro/1
128.185.125.24  128.185.126.24    8      0     0       0    Pro/1


Neighbor addr	Displays the neighbor address.
Neighbor ID	Displays the neighbor's OSPF router ID.
Neighbor State	Can be one of the following: 1 (Down), 2 (Attempt), 4 (Init), 8 (2-Way), 16 (ExStart), 32 (Exchange), 64 (Loading) or 128 (Full).
LSrxl	Size of the current link state retransmission list for this neighbor.
DBsum	Size of the database summary list waiting to be sent to the neighbor.
LSreq	Number of more recent advertisements that are being requested from the neighbor.
Ifc	Interface shared by the router and the neighbor.

Example: neighbor 128.185.138.39

The meaning of most of the displayed fields is given in section 10 of the OSPF specification (RFC 1131).

Neighbor IP address:    128.185.184.34
OSPF Router ID:         128.185.207.34
Neighbor State:         128
Physical interface:     Eth/1
DR choice:              128.185.184.34
Backup choice:          128.185.184.11
DR Priority:            1
Nbr options:            E,MC

DB summ qlen:      0  LS rxmt qlen:      0  LS req qlen:       0
Last hello:        7

# LS rxmits:     108  # Direct acks:    13  # Dup LS rcvd:   572
# Old LS rcvd:     2  # Dup acks rcv:  111  # Nbr losses:     29
# Adj. resets:     30


Neighbor IP addr	Neighbor IP address.
OSPF router ID	Neighbor's OSPF router ID.
Neighbor State	Can be one of the following: 1 (Down), 2 (Attempt), 4 (Init), 8 (2-Way), 16 (ExStart), 32 (Exchange), 64 (Loading) or 128 (Full).
Physical interface	Physical interface type and number of the router and neighbor's common network.
DR choice, backup choice, DR priority	Values in the last hello received from the neighbor.
Nbr options	Optional OSPF capabilities the neighbor supports. These capabilities are E (processes type 5 externals; when this is not set, the area to which the common network belongs is configured as a stub), T (can route based on TOS) and MC (can forward IP multicast datagrams). This field is valid only for those neighbors in state Exchng or greater.
DBsumm qlen	Advertisements waiting to be summarized in Database Description packets. It should be zero except when the neighbor is in state Exchange.
LS rxmt qlen	Advertisements that have been flooded to the neighbor, but not yet acknowledged.
LS req qlen	Advertisements that are being requested from the neighbor in state Loading.
Last hello	Seconds since a hello was received from the neighbor.
# LS rxmits	Retransmissions that occurred during flooding.
# direct acks	Responses to duplicate link state advertisements.
# Dup LS rcvd	Duplicate retransmissions that occurred during flooding.
# Old LS rcvd	Old advertisements received during flooding.
# Dup acks rcvd	Duplicate acknowledgements received.
# Nbr losses	Number of times the neighbor has transitioned to Down state.
# Adj. resets	Counts entries to state ExStart.

Ping [M]

Ping uses the ICMP protocol's ECHO_REQUEST datagram to elicit an ICMP ECHO_RESPONSE from the specified host or network gateway. Ping is generally used to test for reachability between network nodes.

Syntax: ping address

Example: ping 10.1.155.29

-----------10.1.151.29 PING Statistics-------------
7 packets transmitted, 7 packets received, 0% packet loss

Routers [M]

Displays routes that OSPF has calculated and are now present in the routing table.

Note: The routers command shows only border routers, used to calculate inter-area routes, and boundary routers, used to calculate external routes.

Syntax: routers

Example: routers

DType RType Destination       Mask          Cost   Next hop(s)
ASBR  SPF   128.185.142.9    FFFFFFFF        1   128.185.142.9   
Fadd  SPF   128.185.142.98   FFFFFFFF        1    0.0.0.0         
Fadd  SPF   128.185.142.7    FFFFFFFF        1    0.0.0.0         
Fadd  SPF   128.185.142.48   FFFFFFFF        1    0.0.0.0         
Fadd  SPF   128.185.142.111  FFFFFFFF        1    0.0.0.0         
Fadd  SPF   128.185.142.38   FFFFFFFF        1    0.0.0.0         
Fadd  SPF   128.185.142.11   FFFFFFFF        1    0.0.0.0         
  BR  SPF   128.185.142.9    FFFFFFFF        1   128.185.142.9   
  BR  SPF   128.185.142.9    FFFFFFFF        2   128.185.184.114 
Fadd  SPF   128.185.142.47   FFFFFFFF        1    0.0.0.0


DType	Destination type. Net— The destination is a network. ASBR— The destination is an AS boundary router. ABR— The destination is an area border router, and Fadd— A forwarding address (for external routes).
RType	Route type and how the route was derived. SPF— The route is an intra-area route (comes from the Dijkstra calculation), SPIA— The route is an inter-area route (comes from considering summary link advertisements).
Destination	Destination router's OSPF ID. For Type D entries, one of the router's IP addresses is displayed (which corresponds to a router in another AS).
Mask	Always displayed as FFFFFFFF.
Cost	Displays the route cost.
Next hop	Address of the next router on the path toward the destination host. A number in parentheses at the end of the column indicates the number of equal-cost routes to the destination.

Set [C]

Establishes or changes the configuration information of OSPF areas, interfaces, or virtual links. This command also lets you set the way in which OSPF routes are compared to information obtained from other routing protocols.

Syntax: set

area
comparison
interface
virtual-link

area

Sets the parameters for an OSPF area. If no areas are defined, the router software assumes that all the router's directly attached networks belong to the backbone area (area ID 0.0.0.0).

Example: set area

Area number [0.0.0.0]? 0.0.0.1
Is this a stub area? [No]: yes
Stub default cost [0]?
Import summaries? [Yes]:  



Area number

OSPF area address. An OSPF area is a contiguous group of networks defined by a list of address ranges, each indicated by a combination of the IP address and an address mask. A network belongs to an area if its address is in the list. 

Stub area?

If you designate yes,

The area does not receive any AS external link advertisements, reducing the size of your database and decreasing memory usage for routers in the stub area. 

You cannot configure virtual links through a stub area. 


You cannot configure a router within the stub area as an AS boundary router. 



External Routing in Stub Areas

You cannot configure the backbone as a stub area. External routing in stub areas is based on a default route. Each border area router attaching to a stub area originates a default route for this purpose. The cost of this default route is also configurable with the set area command.

Import summaries

???

Area number	OSPF area address. An OSPF area is a contiguous group of networks defined by a list of address ranges, each indicated by a combination of the IP address and an address mask. A network belongs to an area if its address is in the list.
Stub area?	If you designate yes, The area does not receive any AS external link advertisements, reducing the size of your database and decreasing memory usage for routers in the stub area. You cannot configure virtual links through a stub area. You cannot configure a router within the stub area as an AS boundary router.
External Routing in Stub Areas	You cannot configure the backbone as a stub area. External routing in stub areas is based on a default route. Each border area router attaching to a stub area originates a default route for this purpose. The cost of this default route is also configurable with the set area command.
Import summaries	???

comparison

Tells the router where the EGP/RIP/static routes fit in the OSPF hierarchy. The two lower levels consist of the OSPF internal routes. OSPF internal routes take precedence over information gained from any other sources, all of which are located on a single level.

Example: set comparison

Compare to type 1 or 2 externals [2]?

interface

Sets the OSPF parameters for the router's network interfaces.

Example: set interface

Interface IP address [0.0.0.0]? 128.185.123.99
Attaches to area [0.0.0.0]?
Retransmission Interval (in seconds) [5]?
Transmission Delay (in seconds) [1]?
Router Priority [1]?
Hello Interval (in seconds) [10]?
Dead Router Interval (in seconds) [40]?
Type Of Service 0 cost [1]?
Authentication Type (0:NONE, 1:SIMPLE, 2:CRYPTOGRAPHIC) [0]? 2
Message Digest Key ID [0]? 4
MD5 Key?
Retype MD5 Key?
Override the default OSPF interface-type? [No]: yes
OSPF interface-type override
(1=broadcast, 3=NBMA, 5=point-to-multipoint) [0]? 5
Forward multicast datagrams? [Yes]:
Forward as data-link unicasts? [No]:

If you select interface type 3 (NBMA):
(1=broadcast, 3=NBMA, 5=point-to-multipoint) [0]? 3
Poll Interval [120]?

For the parameters listed below you must enter the same value for all routers attached to a common network.

Hello interval
Dead router interval
Authentication key (if an authentication type of 1 is used)

The first prompt asks for the OSPF area to which the interface attaches. For example, suppose that the interface address mask is 255.255.255.0, indicating that the interface attaches to a subnet (128.185.138.0) of network 128.185.0.0. All other OSPF routers attached to subnet 128.185.138.0 must also have their hello interval set to 10, dead router interval set to 40, and their interface authentication key set to xyz_q.

The default OSPF interface type depends on the physical medium the interface is running over. See the following table.

Authentication Type

Security scheme used for the interface. The choices are:

0 (None)—indicates that no authentication is necessary to pass packets.

1 (Simple)—indicates a simple password; or

2 (Cryptographic)—selects MD5 authentication.

Message Digest Key ID

Default OSPF interface type

For LAN (Ehernet)—Broadcast

For X.25, Frame Relay—Point-to-Multipoint

For PPP—Point-to-Point

Authentication Type	Security scheme used for the interface. The choices are: 0 (None)—indicates that no authentication is necessary to pass packets. 1 (Simple)—indicates a simple password; or 2 (Cryptographic)—selects MD5 authentication.
Message Digest Key ID
Default OSPF interface type	For LAN (Ehernet)—Broadcast For X.25, Frame Relay—Point-to-Multipoint For PPP—Point-to-Point

virtual-link

Configures virtual links between any two area border routers. To maintain backbone connectivity you must have all of your backbone routers interconnected either by permanent or virtual links. Virtual links are considered to be separate router interfaces connecting to the backbone area. Therefore, you are asked to also specify many of the interface parameters when configuring a virtual link.

Example: set virtual-link

Virtual endpt. (Router ID) [0.0.0.0]? 128.185.138.21
Link's transit area [0.0.0.1]? 0.0.0.1
Retransmission Interval (in seconds) [10]? 
Transmission Delay (in seconds) [5]? 
Hello Interval (in seconds) [30]? 
Dead Router Interval (in seconds) [180]? 
Authentication Key []? 3-14159

Size [M]

Displays the number of link state advertisements (LSAs) currently in the link state database, categorized by type.

Syntax: size

Example: size

# Router-LSAs:           7
# Network-LSAs:          6
# Summary-LSAs:          14
# Summary Router-LSAs:   2
# AS External-LSAs:      44
# Group-membership-LSAs: 21

Statistics [M]

Displays statistics generated by OSPF. The statistics indicate how well the implementation is performing, including its memory and network utilization. Many of the fields displayed are confirmation of the OSPF configuration.

Syntax: statistics

Example: statistics

                S/W version:            2.1
                OSPF Router ID:         10.1.26.41
                External comparison:    Type 2
                AS boundary capability: No
                Import external routes: None
                Orig. default route:    No (0,0.0.0.0)
                Default route cost:     (1, Type 2)
                Default forward. addr: 0.0.0.0

Attached areas:                  3 Estimated # external routes:   5000
Estimated # OSPF routers:       50 Estimated heap usage:        464800
OSPF packets rcvd:            3682 OSPF packets rcvd w/ errs:        0
Transit nodes allocated:       192 Transit nodes freed:            177
LS adv. allocated:             460 LS adv. freed:                  431
Queue headers alloc:            32 Queue headers avail:             32

# Dijkstra runs:                86 Incremental summ. updates:        1
Incremental VL updates:         21  Buffer alloc failures:            0
Multicast pkts sent:          2465  Unicast pkts sent:               33
LS adv. aged out:                0  LS adv. flushed:                 86
Incremental ext. updates:       84
External LSA database:
Current state:               Normal 
Number of LSAs:                   0 
Number of overflows:              0


S/W version	OSPF software revision level.
OSPF Router ID	The router's OSPF ID.
External comparison	External route type the router uses when importing external routes.
AS boundary capability	Displays whether external routes are imported.
Import external routes	Displays which external routes are imported.
Orig default route	Displays whether the router advertises an OSPF default route. If the value is Yes and a non-zero number is displayed in parentheses, then a default route is advertised only when a route to the network exists.
Default route cost	Cost and type of the default route (if advertised).
Default forward addr	Forwarding address specified in the default route (if advertised).
Attached areas	Number of areas that the router has active interfaces to.
Estimated heap usage	Link state database size estimate in bytes.
Transit nodes freed	Allocated to store router links and network links advertisements.
LS adv. allocated	Allocated to store summary link and AS external link advertisements.
Queue headers alloc	Form lists of link state advertisements used in the flooding and database exchange processes. If the number of queue headers allocated is not equal to the number freed, database synchronization with some neighbor is in progress.
# Dijkstra runs	How many times the OSPF routing table has been calculated from scratch.
Incremental summ updates; Incremental VL updates	New summary link advertisements have caused the routing table to be partially rebuilt.
Buffer alloc failures	Buffer allocation failures. OSPF recovers from temporary lack of packet buffers.
Multicast pkts sent	Covers OSPF hello packets and packets sent during the flooding procedure.
Unicast pkts sent	Covers OSPF packet retransmissions and the Database Exchange procedure.
LS adv. aged out	The number of advertisements that have hit 60 minutes. Link state advertisements age out after 60 minutes. Usually they are refreshed before this time.
LS adv. flushed	The number of advertisements removed (and not replaced) from the link state database.
Incremental ext. updates	Displays number of changes to external destinations that are incrementally installed in the routing table.
External LSA database

Using the OSPF Protocol

Configuring OSPF

OSPF Commands

Introducing OSPF

OSPF Interface Types

OSPF Routers

OSPF Routing Summary

Defining Backbone and Attached OSPF Areas

Setting OSPF Interfaces

Enabling Multicast Forwarding

Setting Non-Broadcast Network Parameters

Other Configuration Tasks

Configuring for Routing Protocol Comparisons

Table 1 OSPF Commands

range area# IP-address IP-address-mask

neighbor

Advertisement [M]

Delete [C]

range area# IP-address

area area#

virtual-link

Disable [C]

as

Dump [M]

as

multicast

subnet

Exit [C] [M]

IGMP [C] [M]

Interface [M]

all

virtual-link

Mcache [M]

Routers [M]

area

comparison

interface

Size [M]

Statistics [M]