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The "Big show" and "Big D" for EIGRPCisco offers some useful tools for determining how EIGRP is working. Perhaps one of the best and most overlooked commands is show ip eigrp neighbors. EIGRP neighbors remind me of an old Robert Frost poem that said, "Good fences make good neighbors." Well, in EIGRP, "Good networks make good neighbors." The neighbor state is absolutely critical to EIGRP operations. Besides providing the capability to assess neighbor states, Cisco offers tools to look at the EIGRP topology table, as well as providing detailed logging of EIGRP events. The following is a list of what we find to be the most useful show, logging, and debug commands for EIGRP: show ip eigrp neighbors [ as_number interface_name ] show ip eigrp topology [ as_number active pending summary ] [ as_number subnet subnet_mask ] show ip protocols [summary] show ip route debug eigrp packets eigrp log-neighbor-changes show ip eigrp neighbors CommandThis can be one of the most useful commands when verifying the operational status of EIGRP. The show ip eigrp neighbors command shows the status of all EIGRP neighbors. The neighbor should be "up" for as long as EIGRP has been running on the link. EIGRP forms a neighbor relationship with all routers on the same subnet and in the same AS. EIGRP does not form a neighbor relationship with mismatched k values; however, a neighbor can be formed with mismatched hellos and dead timers. A neighbor with a short uptime is a clear indication of a problem. Another important field is the queue count. This field indicates the number of packets waiting to be transmitted to that neighbor. This value should be 0 or a number under 20. Consistent Q values in the range of 60 or greater are considered high. A high SRTT number can mean that the packet is experiencing some type of delay on the link. Example 11-8 provides some sample output from the show ip eigrp neighbor command, which provides the basis for an explanation of the other fields, which follows . Example 11-8 show ip eigrp neighbor Command Performed on the grinch Router grinch# show ip eigrp neighbors IP-EIGRP neighbors for process 2001 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 1 172.16.1.5 Se0.1 136 05:48:23 36 1302 0 15 0 172.16.1.6 Se0.1 131 05:48:24 40 1302 0 17 grinch#
NOTE Just because a network appears in the route table does not necessarily mean that "routing" is working properly. In some instances, such as timer mismatches , networks can "phase" in and out of the route table. It is important to look at other things, such as neighbors and databases, to get a clearer view of whether "routing" is actually working properly. show ip eigrp topology CommandThis command lists the EIGRP topology table discussed earlier. The table lists all routes that EIGRP is aware of and shows whether EIGRP is actively processing information on that route. Under most normal conditions, the routes should all be in a passive state and no EIGRP process are running for that route. If the routes are active, this could indicate the dreaded stuck in active, or SIA, state, which is discussed in more detail in an upcoming section. The show ip eigrp topology command also can be extended to show information about an individual route or subnet. This information includes all relevant information about the route, including all its metrics and successors, as well as how the route was learned. Example 11-9 illustrates the use of show ip eigrp topology, followed by the extended version of the command. Example 11-9 EIGRP Topology Table of the grinch Routergrinch# show ip eigrp topology IP-EIGRP Topology Table for process 2001 Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - Reply status P 172.16.5.0/24, 1 successors, FD is 23394560 via 172.16.1.5 (23394560/281600), Serial0.1 P 172.16.6.0/24, 1 successors, FD is 23394560 via 172.16.1.6 (23394560/281600), Serial0.1 P 172.16.1.0/24, 1 successors, FD is 23368960 via Connected, Serial0.1 P 172.16.2.0/24, 1 successors, FD is 281600 via Connected, Ethernet1 grinch# grinch# show ip eigrp topology 2001 172.16.5.0 255.255.255.0 IP-EIGRP topology entry for 172.16.5.0/24 State is Passive, Query origin flag is 1, 1 Successor(s), FD is 23394560 Routing Descriptor Blocks: 172.16.1.5 (Serial0.1), from 172.16.1.5, Send flag is 0x0 Composite metric is (23394560/281600), Route is Internal Vector metric: Minimum bandwidth is 112 Kbit Total delay is 21000 microseconds Reliability is 254/255 Load is 1/255 Minimum MTU is 1500 Hop count is 1 grinch# The fields to note in this output are as follows:
show ip protocols CommandThis command displays all routing protocols, detailed timer and metric information, as well as routing update information. Example 11-10 lists the output of the show ip protocols command. Example 11-10 show ip protocols Command Outputgrinch# show ip protocols Routing Protocol is "eigrp 2001" AS system ID Outgoing update filter list for all interfaces is Incoming update filter list for all interfaces is Default networks flagged in outgoing updates Default networks accepted from incoming updates EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0 'K' values EIGRP maximum hopcount 100 EIGRP maximum metric variance 1 Redistributing: eigrp 2001 Automatic network summarization is in effect Auto-summary in effect Routing for Networks: 172.16.0.0 Networks running EIGRP Routing Information Sources: Gateway Distance Last Update 172.16.1.5 90 00:08:48 Routes reported, and administrative 172.16.1.6 90 00:08:52 distance of the route. Distance: internal 90 external 170 Default admin distance grinch# show ip route CommandThis command lists the router's current route or forwarding table. The output lists what routing protocol the route is from ”in this case, D for EIGRP internal routes and D EX for routes redistributed into EIGRP. The number behind the route is the administrative distance of the route, followed by the composite metric of the route. The via field explains where the route is from, how long ago an update was received, and by what interface it was received. Example 11-11 lists the output of this command. Example 11-11 show ip route Command Output grinch# show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR Gateway of last resort is not set 172.16.0.0/24 is subnetted, 4 subnets D 172.16.5.0 [90/23394560] via 172.16.1.5, 00:17:51, Serial0.1 D 172.16.6.0 [90/23394560] via 172.16.1.6, 00:29:06, Serial0.1 C 172.16.1.0 is directly connected, Serial0.1 C 172.16.2.0 is directly connected, Ethernet1 grinch# debug eigrp packets CommandThe "Big D" command for EIGRP, is just that: big. As discussed earlier, debugs always should be used in conjunction with logging. However, some EIGRP debugs can be so big that additional debugs are needed to control the output of the original debug command. One such case is the debug eigrp packets command. Use the debug eigrp packets command to verify that EIGRP hellos are being exchanged and that adjacencies are being established. Each EIGRP packet sent and received is listed in this output. The output of this command can be controlled with further debugs, such as debug ip eigrp [neighbor as_number IP_address_of_neighbor]. Use the debug ip eigrp command. Use this command with caution and only to look further into a problem. Do not start troubleshooting EIGRP with this command. Example 11-12 lists the output of the debug eigrp packets command. Example 11-12 debug eigrp packets Command Output grinch# debug eigrp packets 06:22:29: EIGRP: Received HELLO on Serial0.1 nbr 172.16.1.5 06:22:29: AS 2001, Flags 0x0, Seq 0/0 idbQ 0/0 06:22:29: EIGRP: Enqueueing UPDATE on Serial0.1 nbr 172.16.1.5 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 2-10 06:22:29: EIGRP: Requeued unicast on Serial0.1 06:22:29: EIGRP: Sending UPDATE on Serial0.1 nbr 172.16.1.5 06:22:29: AS 2001, Flags 0x1, Seq 7/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 2-10 eigrp log-neighbor-changes CommandEIGRP also offers a unique logging command that can be useful when trying to isolate problems on your network. Use the router command eigrp log-neighbor-changes to verify any loss of EIGRP neighbors. Example 11-13 lists the log after an EIGRP hold time has expired . Example 11-13 EIGRP Log After a Neighbor Change grinch(config-router)# eigrp log-neighbor-changes 06:42:12: %DUAL-5-NBRCHANGE: IP-EIGRP 2001: Neighbor 172.16.1.6 (Serial0.1) is d own: holding time expired |
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