The assignment of AppleTalk network numbers and zone names to IOS devices and interfaces is necessary but not sufficient for AppleTalk devices to communicate with each other. To pass data back and forth, the workstations and servers on the AppleTalk network also must know which paths to take to reach one another. AppleTalk routers build and refer to tables of network numbers , which are known as routing tables. The AppleTalk routing tables operate much like IP routing tables, providing network path information that allows the router to deliver data directly to the end destination or to the next router in the path to the end destination. To determine where AppleTalk networks are located, and to share that information with one another, routers employ routing algorithms, also known as routing protocols.
Within AppleTalk, routing protocols can be either static or dynamic in nature. In static protocols, you manually configure the AppleTalk routing table with the network path information. Dynamic routing protocols rely on the routers themselves to advertise information about the different AppleTalk networks to which they are attached. AppleTalk uses two different dynamic routing protocols, which are examined in the section "Configuring AppleTalk Routing Protocols," later in this chapter.
Configuring AppleTalk Routing Commands
Before the router can be configured with AppleTalk protocol information and can begin passing AppleTalk traffic, AppleTalk routing must be enabled. Cisco IOS devices do not automatically enable AppleTalk routing, as they do with TCP/IP.
To enable AppleTalk routing, the IOS global configuration command appletalk routing is used. In the following example, we enable AppleTalk routing on the ZIP router SF-2:
SF-2# configure Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CTRL+Z. SF-2(config)# appletalk routing SF-2(config)# ^Z
After AppleTalk routing is enabled, the router builds the routing table used for switching packets. By default, when an AppleTalk address or cable-range is configured on a LAN or WAN interface and that interface is placed in an operational state, the AppleTalk network information for the interface is placed in the routing table. All operational interfaces connected to the router are placed in the routing table. If only one router is in your network, it contains information about all of its connected AppleTalk networks. Only when two or more routers exist in the network are dynamic routing table entries created. These dynamic routing table entries are created using Routing Table Maintenance Protocol (RTMP), which we discuss later in this chapter.
You can use the IOS EXEC command show appletalk route to view the AppleTalk routing table. When the command is entered with no parameters, the entire AppleTalk routing table is displayed. The following example shows the SF-2 router on the ZIP network, with only the connected operational interfaces and no additional routing table entries:
SF-2# show appletalk route Codes: R - RTMP derived, E - EIGRP derived, C - connected, A - AURP S - static P - proxy 3 routes in internet The first zone listed for each entry is its default (primary) zone. C Net 1-10 directly connected, Fddi0, zone SF Zone C Net 101-150 directly connected, Ethernet1, zone Sales C Net 151-200 directly connected, Ethernet0, zone Marketing
The show appletalk route command provides useful data to the network administrator. It is the key tool used to determine what path an AppleTalk packet follows through the network. The output of this command is similar to the show ip route command that displays the IP routing table, as discussed in Chapter 4.
The first section of output is the legend for the first column of the table. It tells you from where a route was derived. Each of the last three lines in this AppleTalk routing table shows a single route to a set of AppleTalk networks specified as cable-ranges, how the routes were derived, the zones to which the networks belong, and the interface associated with the routes. The "C" in the first column indicates that all the routes are known from operational connected AppleTalk networks. We further explore the show appletalk route command in the section "Verifying AppleTalk Routing Configuration," later in this chapter.
Configuring Static Routing
In the discussion of IP routing in Chapter 4, we introduced various reasons for using static IP routes, including unstable network links and dialup network connections. The same reasons can be applied to the use of static AppleTalk routes. You can use the global configuration command appletalk static to configure static AppleTalk routes in the AppleTalk routing table. In the following example, the ZIP SF-2 router is configured with a static route that directs AppleTalk packets destined to network 40000-40000 to a node 5.10, which is found on the FDDI. In this example, the zone name SF Zone is associated with the cable-range 40000 “40000 by the appletalk static command:
SF-2# configure Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CTRL+Z. SF-2(config)# appletalk static cable-range 40000-40000 to 5.10 zone SF Zone SF-2(config)# ^Z
Using the show appletalk route command, we can verify the entry of the static route in the SF-2 router's routing table:
SF-2# show appletalk route Codes: R - RTMP derived, E - EIGRP derived, C - connected, A - AURP S - static P - proxy 4 routes in internet The first zone listed for each entry is its default (primary) zone. C Net 1-10 directly connected, Fddi0, zone SF Zone C Net 101-150 directly connected, Ethernet1, zone Sales C Net 151-200 directly connected, Ethernet0, zone Marketing S Net 40000-40000 [1/G] via 5.10, 315 sec, Fddi0, zone SF Zone
AppleTalk static routes also can be viewed with the IOS EXEC command show apple static :
SF-2# show apple static AppleTalk Static Entries: ---------------------------------- Network NextIR Zone Status 40000- 40000 5.10 SF Zone A
Verifying AppleTalk Routing Configuration
As examined earlier, AppleTalk routing configuration can be verified using the IOS EXEC command show appletalk route . In this section, we explore additional commands that aid in verifying and managing AppleTalk routing table configuration.
The show appletalk route command is the tool used to view the state of the AppleTalk routing table. Whether static routes are configured or dynamic routing protocols are running, this command shows whether the routes that have been configured or that are expected to be learned are actually present on the router. We explore dynamic AppleTalk routing protocols in the next section of this chapter. Following is an excerpt from the output of the show appletalk route command on the ZIP SF-2 router:
SF-2# show appletalk route Codes: R - RTMP derived, E - EIGRP derived, C - connected, A - AURP S - static P - proxy 5 routes in internet The first zone listed for each entry is its default (primary) zone. C Net 1-10 directly connected, Fddi0, zone SF Zone C Net 101-150 directly connected, Ethernet1, zone Sales C Net 151-200 directly connected, Ethernet0, zone Marketing R Net 11-100 [1/G] via 2.12, 10 sec, Fddi0, zone Operations S Net 40000-40000 [1/G] via 5.10, 315 sec, Fddi0, zone SF Zone
In the preceding output, we see routes to the directly connected AppleTalk networks on the SF-2 router and a dynamically learned route to AppleTalk network 11-100, which is learned from the SF-1 router by using the AppleTalk dynamic routing protocol RTMP. The output also provides the following information:
As with the show ip route command, you can view a specific route using the show appletalk route command by specifying a network number as a parameter. You can also clear AppleTalk routes from the routing table using the privileged EXEC command clear appletalk route . When troubleshooting AppleTalk routing problems, you can use this command to manually clear a route and then use show appletalk route to verify from where the router originally learns that route.
AppleTalk zone name configuration can be verified using the IOS EXEC command show appletalk zone . When no zone name is supplied as a parameter to the command, all zone names are displayed. The following is an excerpt from the output of show appletalk zone from the ZIP SF-2 router:
SF-2# show appletalk zone Name Network(s) SF Zone 1-10 40000-40000 Sales 101-150 Marketing 151-200 Operations 11-100 Total of 4 zones
When two or more AppleTalk routers are present on a network, they exchange dynamic routing information. The IOS EXEC command show appletalk neighbors can be used to verify that AppleTalk routing is enabled and to verify the existence of other AppleTalk routers on the network. The following example is an excerpt from the output of the show appletalk neighbors command on the SF-2 router. It shows that the SF-2 router has learned about its AppleTalk neighbor router SF-1 and that SF-1 is running the dynamic routing protocol RTMP:
SF-2# show appletalk neighbors AppleTalk neighbors: 2.12 SF-1.Fddi0 Fddi0, uptime 33:27, 2 secs Neighbor is reachable as a RTMP peer