Using the AppleTalk Protocol
This document describes the OpenROUTE Networks implementation of the AppleTalk® protocol. It includes the following sections:
AppleTalk Overview
The AppleTalk Protocol Stack
Features Supported
Configuration Procedures
AppleTalk Commands
AppleTalk Overview
At the basic level of the AppleTalk network, connected devices are known as nodes. Nodes can be personal computers, file servers, print servers, and routers. At the next level are networks. A network is a group of nodes connected to a single logical cable. Groups of networks connected by routers or bridges comprise an internet. User-defined groups of nodes from one or more networks within an internet are zones.
The OpenROUTE Networks implementation of AppleTalk supports Ethernet, Token Ring, and FDDI LAN connections and PPP, Frame Relay, and ISDN WAN connections. Figure 1 shows a sample of an AppleTalk internet.
Figure 1 Sample AppleTalk Internet
AppleTalk Addressing
AppleTalk nodes use a 24-bit internet address. A 16-bit network number and an 8-bit node number (node ID). The node ID is an 8-bit number that, when combined with the AppleTalk network number of a node, uniquely identifies each node on a network. Values 0, 254, and 255 are invalid.
Network Range
You can assign more than one network number to an AppleTalk network by assigning a network range. The network range is set of consecutive network numbers. Each network within the AppleTalk internet is assigned a unique, non-overlapping network range. This allows you to have more than 253 devices on one network. Each network can have (253 x network range) nodes.
Dynamic Addressing
AppleTalk uses dynamic addressing. With this process, AppleTalk hosts on the network negotiate a device's node number. A node first tries the node number that was its most recent address. If that value is not available, the node then searches for the next available address. If it reaches 254 without finding an available node number, it tries the next network number in the range.
Seed Routers
With dynamic addressing, you do not need to specify all fields of an AppleTalk address to configure a router. If a preconfigured AppleTalk router, known as seed router, is on the network, it supplies network numbers for new routers. The seed router sends out the address information to all other routers on its connected network. The seed router must come up first and verify the configuration of the other routers. If the configuration is valid, the other routers start functioning. Routers that are not seed routers must first communicate with a seed router before they can function.
As long as one seed router exists on each the network, you do not need to configure the other interfaces and routers connected to that cable because they obtain their routing information from the seed. There are usually several seed routers on a network in case one of them fails. Also, a router can be a seed router for some or all of its network interfaces.
Nonseed Routers
A nonseed router cannot begin routing until the router determines its network number. If you set the network number to zero, the interface does not forward any packets until it receives a valid network number. Upon receiving a Routing Table Maintenance Protocol (RTMP) update, the router is informed of the network number for the interface receiving the packet with the update. Every table update contains the network number of the network on which the packet was sent. Through this exchange, the router determines the network number of the receiving interface.
The AppleTalk Protocol Stack
Figure 2 shows the AppleTalk protocols that this implementation supports along with the corresponding Open Systems Interconnection (OSI) protocol layers.
Figure 2 AppleTalk Protocol Stack and
Corresponding OSI Protocol Layer
These protocols are described in the next sections.
TLAP and ELAP
This implementation supports TLAP and ELAP at the data link layer to transmit AppleTalk packets on Token Ring and Ethernet networks. LocalTalk Link Access Protocol (LLAP) is not supported.
AARP
Each node on the network must have a unique hardware address, for example, a 48-bit Ethernet node address.
Ethernet node addresses are derived from the hardware address or from a user-defined initial address. When an Ethernet AppleTalk node dynamically assigns a node address, the AARP probe confirms that the address is unique. If the address is not unique, it selects a new address. AARP maintains a set of AppleTalk protocol-to-hardware address mappings for the AppleTalk protocol. AARP stores and updates these address mappings in an address mapping table.
DDP
This network layer protocol is responsible for forwarding AppleTalk packets from a source node to a destination node.
RTMP
RTMP specifies how AppleTalk maintains the routing table for the entire internet.
Every 10 seconds RTMP transmits packets with good and suspect entries to routing tables in connected routers. The routers receive these packets and update the corresponding entries to good or suspect. Every 20 seconds RTMP also updates the age of each entry in the routing table. Entries with a state of good become suspect and entries with a state of suspect become bad. After an entry has been bad for 20 seconds, RTMP deletes the entry.
RTMP updates and maintains routing table hop counts, and it deletes all entries with a hop count of 16 or greater.
Hosts can send RTMP request packets to a router on an internet to learn the local network number. The router responds with an RTMP response packet.
NBP
AppleTalk uses entity names to specify the function, attributes, and location of an entity in a network. The Name Binding Protocol maps these human- readable names to machine-readable addresses.
An entity name is an 8-bit ASCII character string that has three fields: object, type, and zone. Each of these fields is a string of not more than 32 characters.
EP
The Echo Protocol tests whether or not a destination is reachable by sending an Echo Request packet to a node on the internet. If the packet reaches the node, the node responds with an Echo Response packet.
ZIP
ZIP allows routers to learn zone names. It keeps a list of zone names and associated network numbers in the Zone Information Table (ZIT).
ZIP requires routers to transmit ZIP queries every ten seconds for each network in the routing table that does not have a zone name. If the receiving router knows the zone name and network number mapping, it responds with a ZIP Reply packet. Using this query-reply method, eventually all the routers will have identical information in their ZITs. Hosts obtain ZIT data by sending and receiving ATP packets to and from the router.
Features Supported
This section describes the following features supported in this implementation of AppleTalk:
Filtering Zone Names and Network Numbers
Zone name filtering and network number filtering increases security and makes it easier to administrate the internet.
Zone name filtering restricts access to zones by filtering the zones that are visible to clients. This feature enhances security, and, since users are presented with a limited number of zones from which to choose, it increases usability.
While zone name filtering lets you partially filter a network, network number filtering lets you completely filter a network. This further increases security and makes administrating the internet easier.
See Setting Up Zone Filters and Setting Up Network Filters for information on how to configure zone and network number filters.
Split-horizon Routing
The RTMP broadcasts routing information every 10 seconds. In large internetworks where many routers are connected to a backbone, RTMP packets can take up a significant portion of available bandwidth. Split-horizon routing, which is enabled as a default on the router, reduces the size of RTMP packets. To do so, it does not send routing information out of the same port in which it was received. It removes these entries from the RTMP packet.
However, in a partially-meshed Frame Relay network, as shown in Figure 3, the routers at the branches cannot communicate with each other unless the router at headquarters broadcasts all routing information to all other routers. In this case, you need to disable split-horizon on the Frame Relay interface at headquarters. You should leave split-horizon enabled at each of the branches to keep them from generating unnecessary traffic.
Figure 3 Partially-Meshed Frame Relay Network
In partially-meshed Frame Relay networks, you should configure addresses for the AppleTalk interfaces. This prevents the AppleTalk protocol from attempting to dynamically learn addresses, which can fail on partially-meshed Frame Relay networks.
Half Routers
When you connect an interface to a serial line, you can set up the interface as a half router. In half-router mode, the serial line connection is invisible to other routers, but it still transmits AppleTalk routing information and data packets. If you have a half router at one end of a serial line, you must configure the router interface at the other end of the serial line as a half router. This feature makes the router interoperable with other vendor's half routers.
Figure 4 Sample Half Router Configuration
To set up a router interface as a half router, set the network number and node number to zero (0), which are the default settings. Do not assign a zone name to the interface.
Configuration Procedures
This section describes how to configure AP2. The tasks you need to perform are
Optional tasks are
For the configuration changes to take effect, you must restart the router.
To access the AP2 configuration prompt enter protocol ap2 at the Config> prompt.
Config>protocol ap2
AP2 protocol user configuration
AP2 config>
Enabling AP2
If you have multiple routers transferring AP2 packets, specify these parameters for each router.
- 1. Use the enable ap2 command to globally enable AP2 on the router.
AP2 config>enable ap2
- 2. Enable the specific interfaces over which AP2 is to send packets.
AP2 config>enable interface 1
Setting Network Parameters
To set up your router as a seed router, set the network range, a starting node number, and at least one zone name. You can configure some interfaces on a router as seed routers and leave other interfaces as nonseed routers. You must have at least one seed router for each AppleTalk network, and you should configure several seed routers on a network in case one of them fails. Note:
Do not set a network range or a node number for half routers. See Half Routers for more information.
- 1. Use the set net-range command to set the Network Range.
AP2 config>set net-range
Interface # [0]? 1
First Network range number (1-65279, or 0 to delete) []? 1
Last Network range number (1-165279) []? 5
Enter the same first and last values for a single numbered network.
- 2. Use the set node-number command to set the starting node number for the interface. The router AARP probes for this node. If the number is already in use, the router chooses a new number.
AP2 config>set node-number
Interface # [0]? 1
Node number (decimal) []? 23
- 3. Use the add zone command to add one or more zone names for the network attached to the interface. If you define a network range for an interface, you should also define the zone names for the interface. If you did not define a network number, do not define zone names.
AP2 config>add zone
Interface # [0]? 1
Zone name []? Finance
After you have specified the parameters, enter list at the AP2 config> prompt to view your configuration.
Setting Up Zone Filters
Zone filtering lets you filter zones in each direction on each interface. To filter incoming packets, set up an input filter. To filter outgoing packets, set up an output filter. The interface does not re-advertise filtered zone information in the direction that you define. To set up a zone filter:
- 1. Add zone filters to an interface.
To add an input zone filter, use the add zfilter in command. To add an output zone filter, use the add zfilter out command. The software prompts you for the interface number and the name of the zone that you want to filter.
AP2 config>add zfilter in
Interface # [0]? 1
Zone name []? Admin
- 2. Enable the zone filters that you added.
To enable an input zone filter, enter enable zfilter in. To enable an output zone filter, enter enable zfilter out. The software prompts you for the interface number and for whether or not the filter is inclusive or exclusive. Inclusive filters forward only the zone information in a filter. Exclusive filters block only the zone information in a filter.
AP2 config>enable zfilter in
Interface # [0]? 1
INCLUSIVE/EXCLUSIVE [INCLUSIVE]? exc
Following are some examples that explain how to set up zone filters in the internet shown in Figure 5.
Figure 5 Sample AppleTalk Internet
Example 1
This example explains how to filter the Manufacturing zone from all other networks. To do so, you would set up an input filter on Interface 1 of Router A to exclude the Manufacturing zone.
- 1. On Router A, add an input zone filter to Interface 1.
AP2 config>add zfilter in
Interface # [0]? 1
Zone name []? Manufacturing
- 2. Enable the input zone filter and make the filter exclusive.
AP2 config>enable zfilter in
Interface # [0]? 1
INCLUSIVE/EXCLUSIVE [INCLUSIVE]? exc
Manufacturing zone information is now excluded from entering Router A, thereby filtering the zone from the rest of the internet.
Example 2
This example shows how to filter the Manufacturing zone from Network 11-15, but still allow the Manufacturing zone to be visible on Network 1-5. To do so, you would set up an output filter on Interface 3 of Router A to exclude Manufacturing zone information from being forwarded out of Interface 3. The interface will continue to advertise Manufacturing zone information over interfaces 0 and 1 on Router A, making it visible on Network 1-5.
- 1. Add an output zone filter to Interface 3.
AP2 config>add zfilter out
Interface # [0]? 3
Zone name []? Manufacturing
- 2. Enable the output zone filter and make the filter exclusive.
AP2 config>enable zfilter out
Interface # [0]? 3
INCLUSIVE/EXCLUSIVE [INCLUSIVE]? exc
This filter excludes Manufacturing zone information from the output of Interface 3.
Example 3
This example shows how to set up a filter so that the Admin zone is visible on all networks, but the Finance zone is not visible to the rest of the internet.
- 1. Add an input zone filter to Interface 0 on Router A.
AP2 config>add zfilter in
Interface # [0]? 0
Zone name []? Admin
- 2. Enable the input zone filter and make it inclusive.
AP2 config>enable zfilter in
Interface # [0]? 0
INCLUSIVE/EXCLUSIVE [INCLUSIVE]? inc
By setting up this input filter as inclusive, interface 0 forwards only Admin zone information to the rest of the internet.
Setting Up Network Filters
Network filters are similar to zone filters, except they let you filter an entire network. To set up a network filter, follow these steps:
- 1. Add a network filter. Use the add nfilter in command to add an input network filter to an interface. Use the add nfilter out command to add an output network filter to an interface. For example:
AP2 config>add nfilter out
Interface # [0]? 0
First Network range number (decimal)[0]? 11
Last Network range number (decimal) [0]? 15
The network range you enter here must match the range that you assigned to that network.
- 2. Enable the network filter that you added and make it either inclusive or exclusive. Inclusive filters forward only network information in a filter. Exclusive filters block only network information in a filter, and they allow all other network information to be forwarded.
AP2 config>enable nfilter in
Interface # [0]? 0
INCLUSIVE/EXCLUSIVE [INCLUSIVE]? exc
Example
This example shows how to filter Network 6-10 so that it is not visible to Network 16-20 in the internet shown in Figure 6.
Figure 6 Sample AppleTalk Internet

- 1. Add an output network filter for Network 6-10 to Interface 2 on Router B.
AP2 config>add nfilter out
Interface # [0]? 2
First Network range number (decimal) [0]? 6
Last Network range number (decimal) [0]? 10
- 2. Enable the output network filter as exclusive.
AP2 config>enable nfilter out
Interface # [0]? 0
INCLUSIVE/EXCLUSIVE [INCLUSIVE]? exc
This filter excludes all information on Network 6-10 from being forwarded through Interface 2 to Network 16-20.
Enabling Checksumming
As the default, the router does not compute DDP checksums of packets it originates. To enable checksumming, use the enable checksum command.
AppleTalk Commands
Table 1 summarizes and the next sections explain the AppleTalk commands.
Press Space twice after you type a command to display the available options for each command.
[C] means the command is available at the AP2 config> prompt.
[M] means the command is available at the AP2> prompt. To display the AP2> prompt, enter protocol ap2 at the + prompt.
Add [C]
Adds a zone name to an interface, adds a zone name as the default for the interface, or adds network and zone filters.
Syntax: add
- zone
- defaultzone
- nfilter in
- nfilter out
- zfilter in
- zfilter out
zone interface# zonename
You can add one or more zone names for each interface. If you define a network number for an interface, you should also define the zone names for the interface. If you did not define a network number, do not define zone names.
Example: add zone
Interface # [0]? 0
Zone name []? Finance
defaultzone interface# zonename
Adds a default zone name for the interface. If a node on the network requests a zone name that is invalid, the router assigns the default zone name to the node until another zone name is chosen.
If you add more than one default to an interface, the last one added overrides the previous default. If you do not add a default, the first zone name added using the zone command is the default.
Example: add defaultzone
Interface # [0]? 0
Zone name []? Headquarters
nfilter in interface# first-network# last-network#
Adds a network filter to the input of the interface. The network range that you enter must match the network range you set for that interface. You cannot filter only a portion of a network range. For example, if you set a network range of 1-10, and you set up a filter for 5-8, the router filters the full network range of 1-10.
Example: add nfilter in
Interface # [0]? 0
First Network range number (decimal) [0]? 1
Last Network range number (decimal) [0]? 10
nfilter out interface# first-network# last-network#
Adds a network filter to the output of the interface. The network range that you enter must match the network range you set for that interface. You cannot filter only a portion of a network range. For example, if you set a network range of 1-10, and you set up a filter for 5-8, the router filters the full network range of 1-10.
Example: add nfilter out
Interface # [0]? 0
First Network range number (decimal) [0]? 11
Last Network range number (decimal) [0]? 20
zfilter in interface# zonename
Adds a zone name filter to the input of the interface.
Example: add zfilter in
Interface # [0]? 1
Zone name []? Marketing
zfilter out interface# zonename
Adds a zone name filter to the output of the interface.
Example: add zfilter out
Interface # [0]? 0
Zone name []? Corporate
Cache [M]
Displays information about the cache-size entries.
Syntax: cache
Example: cache
Destination Net Number Usage Next Hop
122/2 2 1 127/5
138/5 1 0 127/5
23/7 1 1 Direct
Clear-Counters [M]
Clears all cache usage counters and packet overflow counters that you display using the cache command and counters command.
Syntax: clear-counters
Example: clear-counters
Counters [M]
Displays the number of packet overflows on each network interface that sends and receives AppleTalk packets. Counters also displays the number of times the AppleTalk forwarder input queue was full when the interface received packets.
Syntax: counters
Example: counters
APL2 Input Packet Overflows
Net Count
FR/0 0
Eth/1 4
PPP/2 22
TKR/3 0
Delete [C]
Deletes zone names, network or zone name filters, or deletes all AppleTalk information from an interface.
Syntax: delete
- zone
- nfilter in
- nfilter out
- zfilter in
- zfilter out
- interface
zone interface# zonename
Deletes a zone name from the interface zone list.
Example: delete zone
Interface # [0]? 2
Zone name []? corporate
nfilter in interface# first-network# last-network#
Deletes a network filter from the input of the interface. Enter the same network range you set using the add nfilter in command.
Example: delete nfilter in
Interface # [0]? 0
First Network range number (decimal) [0]? 1
Last Network range number (decimal) [0]? 12
nfilter out interface#
Deletes a network filter from the output of the interface. Enter the same network range you set using the add nfilter out command.
Example: delete nfilter out
Interface # [0]? 0
First Network range number (decimal) [0]? 11
Last Network range number (decimal) [0]? 20
zfilter in interface# zonename
Deletes a zone name filter from the input of the interface.
Example: delete zfilter in
Interface # [0]? 1
Zone name []? Marketing
zfilter out interface# zonename
Deletes a zone name filter from the output of the interface.
Example: delete zfilter out
Interface # [0]? 1
Zone name []? Marketing
interface interface#
Deletes all AP2 information for the specified interface. Sometimes this is the only way to delete zone names that have non-printing characters.
Disable [C]
Disables AP2 on all interfaces or on a specified interface, disables checksumming, filtering, or split horizon routing.
Syntax: disable
- ap2
- checksum
- interface
- nfilter in
- nfilter out
- zfilter in
- zfilter out
- split-horizon-routing
ap2
Disables AP2 on all interfaces.
Example: disable ap2
checksum
Specifies that the router does not compute the checksum in packets it generates.
Example: disable checksum
interface interface#
Disables AppleTalk on the specified interface.
Example: disable interface
Interface # [0]? 2
nfilter in interface#
Disables, but does not delete, the input network filters on this interface.
Example: disable nfilter in
Interface # [0]? 2
nfilter out interface#
Disables, but does not delete, the output network filters on this interface.
Example: disable nfilter out
Interface # [0]? 2
zfilter in interface#
Disables, but does not delete, the input zone filters on this interface.
Example: disable zfilter in
Interface # [0]? 1
zfilter out interface#
Disables, but does not delete, the output zone filters on this interface.
Example: disable zfilter out
Interface # [0]? 1
split-horizon-routing interface#
Disables split-horizon routing on this interface. You need to disable split-horizon routing only on Frame Relay interfaces that are on a hub in a partially-meshed Frame Relay network. Disabling split-horizon routing causes all of the routing tables to be propagated on this interface. See Split-horizon Routing for more information.
Example: disable split-horizon-routing
Interface # [0]? 1
Dump [M]
Displays routing table information about the interfaces on the router that forward AppleTalk packets.
Syntax: dump
Example: dump
Dest Net Cost Stat Next hop Source Zone
10-19 0 Dir 0/0 "Ethertalk", "Sales"
40-49 1 Good 10/13 "Marketing",
"CustomrSer","TokenTalk"
20-29 2 Sspct 10/13 "Fuchsia", "Backbone",
"Engineering","MKTING"
You can also use the dump command with a specific interface to display the routes that are visible on that interface. You can use this feature to make sure filters are configured correctly because it shows whether or not filtered zones or networks are visible to an interface.
Example: dump 0
View for interface 0
Dest net Cost State Next hop Zone
214-214 1 Good 152/152 "fddi-214"
153-153 0 Dir "eth153"
152-152 0 Dir "ser152"
3 entries
Enable [C]
Globally enables AP2 on the router or on a specified interface, enables checksumming, network or zone filters, and split-horizon routing.
Syntax: enable
- ap2
- checksum
- interface
- nfilter in
- nfilter out
- zfilter in
- zfilter out
- split-horizon-routing
ap2
Enables the AppleTalk Phase 2 packet forwarder over all of the interfaces on this router.
Example: enable ap2
checksum
Causes the router to checksum all AP2 packets it forwards.
Example: enable checksum
interface interface#
Enables the router to send AppleTalk Phase 2 packets over specific interfaces.
Example: enable interface
Interface # [0]? 1
nfilter in interface# exclusive or inclusive
Enables network input filters and controls how the filter is applied to the interface. Inclusive forwards matches. Exclusive drops matches.
Example: enable nfilter in
Interface # [0]? 1
INCLUSIVE/EXCLUSIVE [INCLUSIVE]? inc
nfilter out interface# exclusive or inclusive
Enables network input filters and controls how the filter is applied to the interface. Inclusive forwards matches. Exclusive drops matches.
Example: enable nfilter in
Interface # [0]? 1
INCLUSIVE/EXCLUSIVE [INCLUSIVE]? exc
zfilter in interface# exclusive or inclusive
Enables and controls how the zone input filter is applied to the interface. Inclusive forwards matches. Exclusive drops matches.
Example: enable zfilter in
Interface # [0]? 0
INCLUSIVE/EXCLUSIVE [INCLUSIVE]? inc
zfilter out interface# exclusive or inclusive
Enables and controls how the zone output filter is applied to the interface. Inclusive forwards matches. Exclusive drops matches.
Example: enable zfilter out
Interface # [0]? 0
INCLUSIVE/EXCLUSIVE [INCLUSIVE]? inc
split-horizon-routing interface#
Enables split-horizon routing on the interface. The default is enabled.
Example: enable split-horizon-routing
Interface # [0]? 1
Exit [C] [M]
Returns to the previous prompt.
Syntax: exit
Example: exit
Interface [M]
Displays the addresses of all interfaces in the router on which AP2 is enabled. If the interface is disabled, this command shows that status.
Syntax: interface
Example: interface
Interface Addresses
PPP/0 0/1 on net 1000-1000 default zone "SerialLine"
Eth/0 10/52 on net 10-19 default zone "Sales"
SL/1 0/0 in startup range
TKR/0 0/0 on net 20-29 default zone "Backbone"
You can also enter interface followed by a specific interface number to view the AP2 configuration of that interface.
Example: interface 1
Eth/0 1/30 on net 1-5 default zone "marketing"
Input Net filters inclusive 1-5
Output Zone filters inclusive "finance"
Output Net filters exclusive 1-5
List [C]
Displays the current AppleTalk configuration. In the example, the router is a seed router on interfaces 0 and 1, and an unseeded router on interface 2. Interface 2 learns the network number and zone name from a seed router.
Syntax: list
Example: list
APL2 globally enabled
Checksumming disabled
Cache size 500
List of configured interfaces:
Interface netrange/ node Zone
0 1000-1000/ 1 "SerialLine" (Def)
Input ZFilters disabled
Input NFilters (inclusive)
Output ZFilters disabled
Output NFilters disabled
Split-horizon-routing enabled
1 10-19/ 52 "EtherTalk","Sales"(Def)
Input ZFilters disabled
Input NFilters (inclusive)
Output ZFilters disabled
Output NFilters disabled
Split-horizon-routing enabled
2 unseeded net/ 0
Input ZFilters disabled
Input NFilters (inclusive)
Output ZFilters disabled
Output NFilters disabled
Split-horizon-routing disabled
Set [C]
Defines the cache-size of fastpath, the network range of seed routers, and the node number.
Syntax: set
- cache-size
- net-range
- node-number
cache-size value
Cache-size corresponds to the number of AppleTalk nodes that can simultaneously communicate through this router using the fastpath feature. (Fastpath is a method of pre-calculating MAC headers to forward packets more quickly.) The default is 500, which allows up to 500 nodes to simultaneously communicate through the router and still use fastpath. If the number of nodes becomes greater than the cache size, the router still forwards the packets, but it does not use fastpath.
You can set cache size from 100 to 10,000. You need to change this default only for very large networks. Although not recommended, setting the cache-size to zero disables the fastpath feature and no memory is used for the cache. Each cache-size entry uses 36 bytes of memory.
Example: set cache-size
number of cache entries (100-10000), or 0 to disable [500]? 700
net-range interface# first# last#
Assigns a network range to the interface. The first number is the lowest number of the network range, and the last number is the highest number of the network range. Legal values are 1 to 65279.
Enter the same first and last values for a single numbered network. To delete the network range for the interface and turn the seeded router into an unseeded router, enter zero for the first and last numbers.
Example: set net-range
Interface # [0]? 1
First Network range number(1-65279, or 0 to delete)[0]? 1
Last Network range number (1-65279) [0]? 15Note:
If you define a network number for an interface, use the add zone command to define the zone names for the interface.
node-number interface# node#
Assigns the starting node number for the router. Legal values are 1 to 253. Zero deletes the node number for the interface and forces the router to choose a number at random. The router AARP probes for this node, and if it is already in use, chooses a new node.
Example: set node-number
Interface # [0]? 2
Node number (1-253, or 0 to delete) []? 45
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