Lab 22: EIGRP Route Redistribution, Summarization, and Stub Routing-Part II

 <  Free Open Study  >  

The "Big show" and "Big D" for EIGRP

Cisco 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 Command

This 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# 
  • Handle (H) ” A Cisco IOS internal number used to identify a neighbor. Do not confuse this with hop count.

  • Neighbor Address ” The adjacent neighbor's IP address. A neighbor should be formed between every router on that subnet running EIGRP in a common AS.

  • Interface ” The interface that is reporting the neighbor.

  • HoldTime ” The amount of time, which counts down, that EIGRP waits for a hello before tearing down the neighbor.

  • Uptime ” Statement of how long the neighbor has been up. This number should be up for as long as the link has been up.

  • Smooth Round Trip Timer (SRRT) ” The number of milliseconds that it takes for an EIGRP packet to be sent to this neighbor and for the local router to receive an acknowledgment ”hence, a round-trip timer. If this number equals 0, a packet has never made a successful round trip.

  • Retransmission TimeOut (RTO) ” The amount of time, in milliseconds, that the EIGRP waits before retransmitting a packet from the retransmission queue to a neighbor.

  • Queue count (Q) ” The number of packets waiting in the queue to be sent out to this neighbor. This value should be 0 or a very low number. A high queue count indicates that data is having trouble getting through.

  • Sequence Number (Seq-Num) ” Sequence number of the last update, query, or reply that was received from this neighbor. If this number equals 0, it indicates that no reliable packets have ever been received from the neighbor, another clear indication of a problem.

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 Command

This 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 Router
 grinch#  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:

  • P ” Passive; no EIGRP computation is being performed. This is the ideal state.

  • A ” Active; EIGRP computations are "actively" being performed for this destination. Routes constantly appearing in an active state indicate a neighbor or query problem. Both are symptoms of the SIA problem.

  • U ” Update; an update packet was sent to this destination.

  • Q ” Query; a query packet was sent to this destination.

  • R ” Reply; a reply packet was sent to this destination.

  • Route information ” IP address of the route or network, its subnet mask, and the successor, or next hop to that network, or the feasible successor.

  • FD ” Feasible distance to the destination network.

  • Send Flag ” The type of packets that need to be sent for the entry.

    - 0x1 The router has received a query for this network and needs to send a unicast reply.

    - 0x2 The route is active, and a multicast query should be sent.

    - 0x3 The route has changed, and a multicast update should be sent.

show ip protocols Command

This 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 Output
 grinch#  show ip protocols   Routing Protocol is "eigrp 2001" graphics/u2190.gif 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 graphics/u2190.gif 'K' values  EIGRP maximum hopcount 100   EIGRP maximum metric variance 1   Redistributing: eigrp 2001  Automatic network summarization is in effect graphics/u2190.gif Auto-summary in effect  Routing for Networks:  172.16.0.0 graphics/u2190.gif Networks running EIGRP  Routing Information Sources:     Gateway         Distance      Last Update  172.16.1.5            90      00:08:48 graphics/u2190.gif Routes reported, and administrative  172.16.1.6            90      00:08:52          distance of the route.  Distance: internal 90 external 170 graphics/u2190.gif Default admin distance  grinch# 

show ip route Command

This 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 Command

The "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 Command

EIGRP 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 
 <  Free Open Study  >  


CCIE Practical Studies, Volume I
CCIE Practical Studies, Volume I
ISBN: 1587200023
EAN: 2147483647
Year: 2001
Pages: 283
Authors: Karl Solie

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net