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Using WAN Reroute

Note: Previous version of OpenROUTE software supported a WAN Restoral feature. Starting in OpenROUTE version 3.0, you can set up WAN Restoral functionality using Multilink PPP. See Multilink PPP and WAN Restoral.

WAN Reroute Overview

WAN Reroute lets you set up an alternate route so that if a primary link fails, the router automatically initiates a new connection to the destination through the alternate route.

The WAN Reroute process involves:

: 1. Detecting the primary link failure
: 2. Switching to the alternate link
: 3. Detecting the primary link recovery
: 4. Switching back to the primary link

You can use any type of link as the alternate link and any type of link as the primary link. The alternate link does not need to be connected to the same end point as the primary link.

Figure 1 shows how WAN Reroute provides an alternate connection between LAN 1 and LAN 2. Normally, there is a connection between routers A and B and routers A and C. If the primary link between routers A and B fails, WAN Reroute establishes an alternate link between routers B and C. Routers A and B can then communicate through router C.

Figure 1 WAN Reroute

Configuring WAN Reroute

The steps to configure WAN Reroute follow, as well as an example of how to perform these tasks.

To configure WAN Reroute:

: 1. Configure the primary link.
: 2. Configure the alternate link.
: 3. Add the alternate link to the primary link. You can also specify a stabilization period for the primary link.

Sample WAN Reroute Configuration

In Figure 2, the router requires a dedicated link to the Internet. The primary connection is over an ISDN link to ISP 1. If the connection to ISP 1 goes down, WAN Reroute establishes an alternate connection to ISP 2.

Figure 2 Sample WAN Reroute Configuration

To set up WAN Reroute on the router in Figure 2, you need to

: 1. Configure the ISDN interface 1 to call ISP 1.
: 2. Add a second ISDN interface 2 and configure it to call ISP 2.
: 3. Add an alternate interface 2 for primary interface 1 and, optionally, assign a stabilization period for the primary link.

The next sections describe these tasks in detail.

Configuring the ISDN Interfaces

Follow these steps to set up the ISDN interfaces in Figure 2 for WAN Reroute.

1. Configure the ISDN interfaces as described in Using the ISDN Interface.

2. Configure interface 1.

Config>network
What is the network number [0]? 1
Circuit Configuration

Circuit Config <NET-1> set destination
Assign destination address name []? isp1
Circuit Config <NET-1> set idle
Idle timer (seconds, 0 means always active) [60]? 30

3. Configure ISDN interface 2.

Config>network
What is the network number [0]? 2
Circuit Configuration
Circuit Config <NET-2> set destination
Assign destination address name []? isp2
Circuit Config <NET-2> set idle
Idle timer (seconds, 0 means always active) [60]? 30

You must configure routing protocols on the interface that WAN Reroute uses as the alternate link. If you cannot prevent those routing protocols from sending maintenance packets, the alternate link establishes a connection, even if rerouting is not necessary. In this case, if you want to use the alternate link only for rerouting, disable the interface.

To disable the interface, enter disable interface at the Config> prompt. Otherwise, configure the interface to dial on demand by setting the idle timer to nonzero. Enter set idle at the Circuit Config <NET-#> prompt.

Assigning and Configuring the Alternate Link

Enter the WAN Reroute configuration process to assign interface 2 as the alternate link for the interface 1 and, if desired, to specify the stabilization periods. There are two types of stabilization periods:

First stabilization period is the amount of time the router waits for the primary interface to become active when the router first attempts to bring it up. If the primary interface does not come up before the first stabilization period expires, WAN Reroute brings up the alternate link.
Stabilization period is the amount of time the router waits to be sure the primary link is reliable before it switches from the alternate link back to the primary link.

Follow these steps to assign and configure the alternate link (interface 2 in Figure 2):

1. Display the WAN Reroute configuration prompt.

Config>feature wrr 
WAN Reroute user configuration

WRR Config>

2. Assign the ISDN interface 2 as the alternate link for the ISDN interface 1.

WRR Config>add alternate-circuit
Alternate interface number  [0]? 2
Primary interface number  [0]? 1

3. Enable the alternate circuit.

WRR Config>enable alternate-circuit
Alternate interface number  [0]? 2

4. Enable WAN Reroute.

WRR Config>enable wrr

5. Optionally, set a first stabilization period.

To set the first stabilization period for a specific primary interface, enter set first-stabilization.

To set a default first stabilization period for all interfaces that do not have specific periods set, enter set default first-stabilization.

WRR Config>set first-stabilization
Primary interface number  [0]? 1
First primary stabilization time (0 - 3600 seconds -1 = default)  [-1]?
WRR Config>set default first-stabilization
Default first primary stabilization time (0 - 3600 seconds)  [0]?

Sample WAN Reroute Configuration Using ISDN and Frame Relay

In Figure 3 branch offices use Frame Relay to connect to headquarters. If a primary link from a branch to headquarters fails, WAN reroute establishes an alternate route to headquarters through another branch. For example, if the Frame Relay DLCI between router A and router C fails, WAN reroute uses the ISDN interface to establish an alternate connection through router D.

Figure 3 Sample WAN Reroute Configuration

To set up WAN reroute on Router A in Figure 3, you need to

: 1. Set up the Frame Relay interface (1) as an FRLANE interface with a required PVC. Or, set up the Frame Relay interface as either FRVC or FRLANE and enable the no-pvc flag on the Frame Relay interface. See Using Frame Relay.
: 2. Configure the ISDN interface (3). See Using the ISDN Interface.
: 3. In the Wan Reroute configuration, assign the ISDN interface as the alternate link for the Frame Relay interface and, optionally, assign a stabilization period for the primary link.

Configuring the Router to Detect Failures Faster

You can adjust the amount of time the router waits before it declares that an interface is down. The default is four seconds. To change this setting, enter set down-notify at the Config> prompt.

Config>set down-notify
Interface number [0]? 1
Down notification time (1 to 300, 0 to restore default)[0]? 2

WAN Reroute Commands

Table 1 lists the WAN Reroute commands.

Not all parameters apply to all router platforms. Press Space twice after you type a command to display the available parameters for each command. Enter help for information about using the command line interface.

[C] means the command is available at the WRR Config> prompt.

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

Table 1 WAN Reroute Commands

Command Function

Add [C] Assigns an alternate interface to a primary interface.

Disable [C] [M] Clears the monitoring statistics displayed using the list command.

Disable [C] [M] Disables WAN Reroute or disables the use of an alternate circuit for WAN Reroute.

Enable [C] [M] Enables WAN Reroute or enables an alternate circuit.

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

List [C] [M] Displays the current WAN Reroute configuration.

Remove [C] Removes the assignment of an alternate interface to a primary interface.

Set [C] Sets a stabilization period for the primary interface.

Table 1 WAN Reroute Commands
Command	Function
Add [C]	Assigns an alternate interface to a primary interface.
Disable [C] [M]	Clears the monitoring statistics displayed using the list command.
Disable [C] [M]	Disables WAN Reroute or disables the use of an alternate circuit for WAN Reroute.
Enable [C] [M]	Enables WAN Reroute or enables an alternate circuit.
Exit [C] [M]	Returns to the previous prompt.
List [C] [M]	Displays the current WAN Reroute configuration.
Remove [C]	Removes the assignment of an alternate interface to a primary interface.
Set [C]	Sets a stabilization period for the primary interface.

Add [C]

Assigns an interface as the alternate to a primary interface for WAN Reroute. You must have previously configured both interfaces. You can assign only one alternate interface to a primary interface.

Syntax: add

alternate-circuit

Example: add alternate-circuit

Alternate interface number  [0]? 4
Primary interface number  [0]? 1

Clear [M]

Clears WAN Reroute statistics that you display using the list command. This command clears Longest restoral period, but does not clear the Most recent restoral period.

Syntax: clear

Example: clear

Disable [C] [M]

Disables WAN Reroute on the router or disables an alternate circuit.

Syntax: disable

alternate-circuit
wrr

alternate-circuit interface#

Disables the alternate interface that you assigned for WAN Reroute. The circuit remains disabled until you enable it again using the enable alternate-circuit command. You must have previously configured both interfaces and bound them together using the add alternate-circuit command.

Note: At the WRR> prompt, this command disconnects any active call on the alternate interface. The interface remains disabled until you restart or reload the router or until you enter enable alternate-circuit.

Example: disable alternate-circuit

Alternate interface number  [0]? 4
Alternate circuit 4 unassigned

wrr

Disables WAN Reroute on the router.

Example: disable wrr

Enable [C] [M]

Enables WAN Reroute on the router or enables an alternate circuit.

Syntax: enable

alternate-circuit
wrr

alternate-circuit interface#

Enables an alternate interface for WAN Reroute. You must have previously assigned the alternate circuit to a primary interface using the add alternate-circuit command.

Example: enable alternate-circuit

Alternate interface number  [0]? 4

wrr

Enables the WAN Reroute feature on the router.

Example: enable wrr

Exit [C] [M]

Returns to the previous prompt.

Syntax: exit

Example: exit

List [C] [M]

Displays configuration information or monitoring statistics as described in the next sections.

List [C]

Displays the current WAN Reroute configuration.

Syntax: list

Example: list

WAN Reroute is enabled.
Default Stabilization Time:       0 seconds
Default First Stabilization Time: 0 seconds
                                                 Alternate    1st  Subseq
   Primary Interface      Alternate Interface    Enabled      Stab  Stab
---------------------  ----------------------   --------     ----  ----
 1 - Basic Rate ISDN      2 - PPP Dial Circuit    Yes         30  dflt

List [M]

Displays statistics on one or all secondary circuits.

Syntax: list

all
alternate-circuit
summary

all

Provides statistics for all secondary circuits and their associated primary interfaces.

Example: list all

WAN Re-route is enabled with 1 circuit configured
    Total reroute attempts =         1  completions   =          1
    Longest completed restoral period in hrs:min:sec     0:30:15  

 Primary       Alternate      Re-route   Re-route    Current/Longest
Net Interface  Net Interface  Enabled    Active       Duration
-------------  -------------  --------  --------   ---------------
 3   PPP/2       4  PPP/3        Yes          No         ---:--:--


Total Re-route attempts	Number of times the primary failed, causing the router to try to bring up an alternate link.
Completions	Number of times WAN Reroute successfully brought up the primary interface as an alternate link.
Longest completed restoral period	Longest amount of time an alternate link was in operation, not counting any current usage.
Primary Interface	Interface that is being backed up by WAN Reroute.
Alternate Interface	Interface that is configured as the alternate to the associated primary for WAN Reroute.
Re-route Enabled	Whether or not WAN Reroute is enabled for these interfaces.
Re-route Active	Whether or not the alternate interface is currently in use.
Current/Longest Duration	If the alternate interface is currently active, shows how long the circuit has been active. not currently active, shows the longest amount of time the circuit has been active.

alternate-circuit interface#

Displays statistics and configuration for individual alternate interfaces and their associated primary interfaces.

Example: list alternate-circuit

Alternate interface number  [0]? 4
Primary    3:PPP/2 Point to Point ISDN Basic Rate 
Alternate  4:PPP/3 Point to Point ISDN Basic Rate 
Enabled, re-route currently inactive
Primary first stabilization time: default (3 seconds) 
Primary stabilization time: default (3 seconds) 
Restored 0 times (0 attempts)

summary

Provides WAN Reroute statistics for all alternate circuits.

Example: list summary

WAN Reroute is enabled with 1 circuit(s) configured
        Total reroute attempts  =          1 completions   =          0
        Longest completed reroute period in hrs:min:sec     0:00:00


Total reroute attempts	Number of times the primary failed, causing the router to try to bring up an alternate link.
Completions	Number of times WAN Reroute successfully backed up the primary interface.
Longest Completed Reroute period	Longest amount of time an alternate linke was in operation, not counting any current usage.

Remove [C]

Deletes the assignment of an alternate interface to the primary interface.

Syntax: remove

alternate-circuit

Example: remove alternate-circuit

Primary interface number  [0]?

Set [C]

Specifies stabilization periods. There are two types of stabilization periods:

First stabilization period is the amount of time the router waits for the primary interface to become active when the router first attempts to bring it up. If the primary interface does not come up before the first stabilization period expires, WAN Reroute brings up the alternate link.
Stabilization period is the amount of time the router waits to be sure the primary link is reliable before it switches from the alternate link back to the primary link.

For both types of stabilization periods, you can set a default, which applies to all interfaces that do not have a stabilization period configured.

Syntax: set

default first-stabilization
default stabilization
first-stabilization
stabilization

default first-stabilization #-of-seconds

Sets a first stabilization period for all interfaces that do not have a first stabilization period configured. The range is 0 to 3600 seconds. The default is 0, which causes the router to bring up the alternate link only if an interface fails the self test.

Example: set default first-stabilization

Default first primary stabilization time (0 - 3600 seconds)  [0]?

default stabilization #-of-seconds

Sets a stabilization period for all interfaces that do not have a stabilization period configured. The range is 0 to 3600 seconds. The default is 0, which causes the router to switch from the alternate link back to the primary link as soon as the primary link becomes active.

Example: set default stabilization

Default primary stabilization time (0 - 3600 seconds)  [0]?

first-stabilization primary-interface# #-of-seconds

Sets a first stabilization period for a specific primary interface. The range is 0 to 3600 seconds. The default is -1, which causes the router to use the default first-stabilization setting.

Example: set first-stabilization

Primary interface number  [0]? 1
First primary stabilization time (0 - 3600 seconds -1 = default) [-1]?

stabilization primary-interface# #-of-seconds

Sets a stabilization period for a specific primary interface. The range is 0 to 3600 seconds. The default is -1, which causes the router to use the default stabilization setting.

Example: set stabilization

Primary interface number  [0]? 1
Primary stabilization time (0 - 3600 seconds, -1 = default)  [-1]?

Testing and Disabling WAN Reroute Circuits

You can test the WAN Reroute alternate interface by entering test at the + prompt. This command brings up the link briefly and then takes it back down.

If you enter disable at the + prompt, the router disconnects the current call, but the alternate interface remains available for WAN Reroute. To disable WAN Reroute, enter disable at the WRR> or WRR Config> prompt.

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