Verifying AppleTalk Connectivity and Troubleshooting

The IOS software offers numerous tools to aid the network administrator in tracking down AppleTalk connectivity problems, network configuration errors, and dynamic routing protocol problems. In this section, we examine IOS EXEC show commands, debug commands, and diagnostic commands that facilitate identifying network issues.

As previously examined, the IOS EXEC command show appletalk interface is a useful tool for identifying network number and zone name misconfigurations, as well as tracking the progress of the AppleTalk interface initialization. The second line of output from this command tracks the status of the initialization and also informs you of any misconfigurations. The following is an example of a misconfiguration caused by missing zone name information on ethernet 0 of the ZIP SF-2 router:

 SF-2#  show appletalk interface ethernet 0  Ethernet0 is up, line protocol is up    AppleTalk node down, Port configuration error    AppleTalk cable range is 151-200    AppleTalk address is 198.72, Invalid    AppleTalk zone is not set.    AppleTalk address gleaning is disabled    AppleTalk route cache is enabled 

The IOS EXEC command show appletalk nbp is useful in determining the network number associated with a particular named resource. The command displays the network.node address associated with a name that is registered with NBP. The network administrator can verify whether the named resource has the expected network.node number, or vice versa. The following is an excerpt from the output of the show appletalk nbp command on the ZIP SF-1 router, which shows its interface registrations with NBP:

 SF-1#  show appletalk nbp  Net   Adr   Skt   Name                 Type            Zone      2   12    254   SF-1.Fddi0           ciscoRouter     SF Zone     22    7    254   SF-1.Ethernet0       ciscoRouter     Operations 

In troubleshooting connectivity problems, it is useful to determine whether a station that should be reachable via a directly connected LAN interface is responding. To verify that the router has been capable of resolving the AppleTalk network address to a MAC address, use the IOS EXEC command show appletalk arp . This command can take as a parameter a specific AppleTalk network.node address. When no parameter is supplied, all AppleTalk ARP entries are displayed. The output of this command includes the AppleTalk address-to-MAC mapping, the age of the entry in the table, and the interface with which the ARP entry is associated. (The router times an ARP entry out of the ARP table after four hours.) Following is an example of the show appletalk arp command on the ZIP SF-1 router:

 SF-1#  show appletalk arp  Address  Age (min)  Type      Hardware Addr        Encap   Interface  2.12            -   Hardware  0000.0c0c.34d1.0000  SNAP    Fddi0  9.159           -   Hardware  0000.0c0c.23d1.0000  SNAP    Ethernet1  5.20            -   Dynamic   0000.030c.11c4.0000  SNAP    Fddi0 

Like TCP/IP, AppleTalk implements an echo request/response protocol called AppleTalk Echo Protocol (AEP). The AEP allows an AppleTalk station to send an echo request to a destination station. When the station receives the request, it sends an echo reply to the originating station. This simple protocol allows network administrators to test the reachability of AppleTalk servers, printers, and other devices. AEP is implemented in the IOS software as the ping appletalk command. In addition to providing basic reachability information, the ping appletalk command informs you of approximately how long the echo request and reply take to reach and return from the destination station. In the following example, the IOS EXEC command ping appletalk sends five 100-byte AEP requests to the given AppleTalk address, as seen on the SF-1 router:

 SF-1#  ping appletalk 5.20  Type escape sequence to abort.  Sending 5, 100-byte AppleTalk Echos to 5.20, timeout is 2 seconds:  !!!!!  Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms 

The router sends five AEP echo requests and reports via the exclamation point (!) that all the replies are received. It also reports the number of echo request attempts and the number of echo replies received. The router then calculates the percentage of successful pings . Minimum, maximum, and average response times are also calculated.

Table 5-4 shows the different response characters that can be received as a result of an AppleTalk ping.

Table 5-4. Ping Command Response Characters

Character	Meaning
!	Each exclamation point indicates the receipt of a reply (echo) from the target address.
.	Each period indicates that the network server timed out while waiting for a reply from the target address.
B	The echo received from the target address was bad or malformed .
C	An echo with a bad DDP checksum was received.
E	Transmission of an echo packet to the target address failed to find a MAC address.
R	Transmission of the echo packet to the target address failed because it lacked a route to the target address.

The ping appletalk command, like its IP counterpart , has both a privileged and a nonprivileged version. In the user EXEC mode, the nonprivileged version allows the user only to specify an AppleTalk address. The privileged version, available in the enable EXEC mode, allows the user to modify parameters of the echo request, including the number of requests, the size of the packets sent, the timeout value, and numerous other values. Following is an example of the privileged version of the ping appletalk command executed on the SF-1 router; the request packet size has been increased to 500 bytes:

 SF-1#  ping appletalk  Target AppleTalk address:  5.20  Repeat count [5]:  Datagram size [100]:  500  Timeout in seconds [2]:  Verbose [n]:  Sweep range of sizes [n]:  Type escape sequence to abort.  Sending 5, 500-byte AppleTalk Echos to 5.20, timeout is 2 seconds:  !!!!!  Success rate is 100 percent (5/5), round-trip min/avg/max = 1/4/6 ms 

Overall information about the performance and operation of AppleTalk on the Cisco router can be obtained using two different IOS EXEC commands. The show appletalk traffic command includes counters for such information as the total number of packets received and sent by the router, the number of broadcasts received and sent, RTMP and EIGRP statistics, and whether the router has sent or received AppleTalk Echoes. The counters in show appletalk traffic are cumulative, and they can be reset with the IOS privileged EXEC command clear appletalk traffic or by reloading or power cycling the router. The following is an example of the output from the show appletalk traffic command on the ZIP Singapore router:

 Singapore#  show appletalk traffic  AppleTalk statistics:    Rcvd:  90 total, 0 checksum errors, 0 bad hop count           45 local destination, 0 access denied, 0 fast access denied           0 for MacIP, 0 bad MacIP, 0 no client           0 port disabled, 0 no listener           0 ignored, 0 martians    Bcast: 0 received, 18766 sent    Sent:  18766 generated, 0 forwarded, 0 fast forwarded, 45 loopback           0 forwarded from MacIP, 0 MacIP failures           25 encapsulation failed, 0 no route, 0 no source    DDP:   135 long, 0 short, 0 macip, 0 bad size    NBP:   30 received, 0 invalid, 0 proxies           0 replies sent, 55 forwards, 25 lookups, 0 failures    RTMP:  0 received, 0 requests, 0 invalid, 0 ignored           17624 sent, 0 replies    ATP:   0 received    ZIP:   0 received, 20 sent, 0 netinfo    Echo:  40 received, 0 discarded, 0 illegal           20 generated, 20 replies sent    Responder:  0 received, 0 illegal, 0 unknown           0 replies sent, 0 failures    AARP:  0 requests, 0 replies, 0 probes           0 martians, 0 bad encapsulation, 0 unknown           153 sent, 0 failures, 0 delays, 25 drops    Lost: 0 no buffers    Unknown: 0 packets    Discarded: 0 wrong encapsulation, 0 bad SNAP discriminator    AURP: 0 Open Requests, 0 Router Downs          0 Routing Information sent, 0 Routing Information received          0 Zone Information sent, 0 Zone Information received          0 Get Zone Nets sent, 0 Get Zone Nets received          0 Get Domain Zone List sent, 0 Get Domain Zone List received          0 bad sequence    EIGRP: 0 received, 0 hellos, 0 updates, 0 replies, 0 queries           1097 sent,     0 hellos, 0 updates, 0 replies, 0 queries 

The second IOS EXEC command to provide general information about AppleTalk operation is the show appletalk globals command. This command provides information about various configuration option settings for the dynamic routing protocols, the number of network routes and zones with the AppleTalk network, and how packets with errors will be handled when they arrive at the router. This command is useful for verifying that the desired configuration options are configured and are operating as expected on your routers. The following example shows the output of the show appletalk globals command on the ZIP SF-1 router:

 SF-1#  show appletalk globals  AppleTalk global information:    Internet is incompatible with older, AT Phase1, routers.    There are 16 routes in the internet.    There are 11 zones defined.    Logging of significant AppleTalk events is disabled.    ZIP resends queries every 10 seconds.    RTMP updates are sent every 10 seconds.    RTMP entries are considered BAD after 20 seconds.    RTMP entries are discarded after 60 seconds.    AARP probe retransmit count: 10, interval: 200 msec.    AARP request retransmit count: 5, interval: 1000 msec.    DDP datagrams will be checksummed.    RTMP datagrams will be strictly checked.    RTMP routes may not be propagated without zones.    Routes will be distributed between routing protocols.    Routing between local devices on an interface will not be performed.    IPTalk uses the udp base port of 768 (Default).    EIGRP router id is: 2500    EIGRP maximum active time is 3 minutes    Alternate node address format will not be displayed.    Access control of any networks of a zone hides the zone. 

In addition to the troubleshooting and verification commands presented in this section, numerous privileged IOS EXEC debug commands exist to aid in determining the operation of the AppleTalk protocol on the router. These debug commands provide both general and detailed diagnostic output that can aid in troubleshooting and in verifying the operation of the router, routing protocols, and other functions. For example, the output from the debug appletalk errors command can help isolate network address and zone name misconfig-urations on router interfaces. Some of the more common debug commands used for AppleTalk are summarized in Table 5-5.

Table 5-5. Debug Commands for AppleTalk

Command	Description
debug appletalk arp	Displays AARP requests generated and replies sent to the router and AARP ager activity.
debug appletalk eigrp-packet	Displays the contents of AppleTalk EIGRP packets sent and received by the router.
debug appletalk eigrp-update	Displays the update activity of the AppleTalk EIGRP on the router.
debug appletalk errors	Displays information about errors that occur with the AppleTalk protocol.
debug appletalk events	Displays significant AppleTalk events that occur on the router.
debug appletalk nbp	Displays the activities of the NBP on the router.
debug appletalk packet	Displays the source and destination AppleTalk addresses of packets that are routed by the router. As with the debug ip packet, this debug command can overload the router, so care must be taken when using it. It is suggested that packet debugging be limited to a particular interface.
debug appletalk routing	Displays changes that occur in the routing table as the result of the addition and deletion of routes for EIGRP and RTMP.
debug appletalk rtmp	Displays changes that occur in the routing table as the result of the addition and deletion of routes for RTMP routes only.
debug appletalk zip	Displays the activities of the Zone Information Protocol on the router.