Verifying EIGRP
You can use several commands, as defined in Table 4.8, on a router to help you troubleshoot
and verify the EIGRP configuration:
key number In key chain configuration mode, identify the key number
key-string text In key chain key configure mode, identify the key string
accept-lifetime start-time (optional) specify the time period during which the key can
be received
send-lifetime start-time (optional) specify the time period during which the key can
be sent
TABLE 4 . 8 Verifying EIGRP
Command Meaning
show ip route eigrp Shows only EIGRP entries in the routing table
show ip eigrp neighbors Shows all EIGRP neighbors
show ip eigrp topology Shows entries in the EIGRP topology table
debug eigrp packet Shows hello packets sent/received between adjacent
routers
debug ip eigrp notification Shows EIGRP changes and updates as they occur on
your network
Now return to the Corp router and see what it shows in the neighbor table:
Corp#sh ip eigrp neighbors
IP-EIGRP neighbors for process 10
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
1 10.1.3.2 Se0/0/1 14 00:35:10 1 200 0 81
3 10.1.5.2 Se0/2/0 10 02:51:22 1 200 0 31
2 10.1.4.2 Se0/1/0 13 03:17:20 1 200 0 20
0 10.1.2.2 Se0/0/0 10 03:19:37 1 200 0 80
You can read the information in this output like this:
The H field indicates the order in which the neighbor was discovered.
The hold time is how long this router will wait for a hello packet to arrive from a specific
neighbor.
The uptime indicates how long the “neighborship” has been established.
The SRTT field is the smooth round-trip timer—an indication of the time it takes for a
round-trip from this router to its neighbor and back. This value is used to determine how
long to wait after a multicast for a reply from this neighbor. If a reply isn’t received in
time, the router will switch to using unicasts in an attempt to complete the communication.
The time between multicast attempts is specified by the Retransmission Time Out
(RTO) field, described next.
RTO is the amount of time EIGRP waits before retransmitting a packet from the retransmission
queue to a neighbor.
The Q value indicates whether there are any outstanding messages in the queue—consistently
large values would indicate a problem.
The Seq field indicates the sequence number of the last update from that neighbor—something
that’s used to maintain synchronization and avoid duplicate or out-of-sequence
processing of messages.
Now let’s see what’s in the Corp topology table by using the show ip eigrp topology
command. This should be interesting!
Corp#sh ip eigrp topology
IP-EIGRP Topology Table for AS(10)/ID(10.1.5.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 10.1.11.0/24, 1 successors, FD is 2172416
via 10.1.5.2 (2172416/28160), Serial0/2/0
P 10.1.10.0/24, 1 successors, FD is 2172416
via 10.1.5.2 (2195456/281600), Serial0/2/0
P 10.1.9.0/24, 1 successors, FD is 2195456
via 10.1.4.2 (2195456/281600), Serial0/1/0
P 10.1.8.0/24, 1 successors, FD is 2195456
via 10.1.4.2 (2195456/72960), Serial0/1/0
P 10.1.12.0/24, 1 successors, FD is 2172416
via 10.1.5.2 (2172416/28160), Serial0/2/0
P 10.1.3.0/24, 1 successors, FD is 76839936
via Connected, Serial0/0/1
via 10.1.2.2 (9849856/7719936), Serial0/0/0, serno 89
P 10.1.2.0/24, 1 successors, FD is 2169856
via Connected, Serial0/0/0
via 10.1.2.2 (2681856/551936), Serial0/0/0
Notice that every route is preceded by a P. This means the route is in the passive state,
which is good because routes in the active state (A) indicate that the router has lost its path
to this network and is searching for a replacement. Each entry also indicates the FD to
each remote network plus the next-hop neighbor through which packets will travel to their
destinations. In addition, each entry also has two numbers in parentheses. The first indicates
the feasible distance, and the second indicates the advertised distance to a remote
network.
Corp#debug eigrp packet
EIGRP Packets debugging is on
(UPDATE, REQUEST, QUERY, REPLY, HELLO, IPXSAP, PROBE, ACK, STUB, SIAQUERY,
SIAREPLY)
Corp#
*Mar 21 23:17:35.050: EIGRP: Sending HELLO on FastEthernet0/1
*Mar 21 23:17:35.050: AS 10, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
*Mar 21 23:17:35.270: EIGRP: Received HELLO on Serial0/1/0 nbr 10.1.4.2
*Mar 21 23:17:35.270: AS 10, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
peerQ un/rely 0/0
*Mar 21 23:17:35.294: EIGRP: Received HELLO on Serial0/0/0 nbr 10.1.2.2
*Mar 21 23:17:35.294: AS 10, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
peerQ un/rely 0/0
*Mar 21 23:17:38.014: EIGRP: Received HELLO on Serial0/2/0 nbr 10.1.5.2
*Mar 21 23:17:38.014: AS 10, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
peerQ un/rely 0/0
Since my Corp router is connected to three EIGRP neighbors and because the 224.0.0.10
multicast is sent out every five seconds, I didn’t have any problem seeing the updates. The
hello packets are sent out every active interface, as well as all the interfaces to which I have
neighbors connected. Did you notice the AS number is provided in the update? This is
because if a neighbor doesn’t have the same AS number, the hello update would just be
discarded.
I’ll now show you one more important debugging command—the debug ip eigrp
notification command (called debug ip eigrp events on pre-12.4 routers), plus the
resulting output. The only time you’ll see output from this command is if there’s a problem on
your network or you you’ve added or deleted a network from a router in your internetwork.
Corp(config)#int f0/1
Corp(config-if)#shut
*Mar 21 23:25:43.506: IP-EIGRP(Default-IP-Routing-Table:10): Callback: route_
adjust FastEthernet0/1
*Mar 21 23:25:43.506: IP-EIGRP: Callback: ignored connected AS 0 10.1.1.0/24
*Mar 21 23:25:43.506: into: eigrp AS 10
*Mar 21 23:25:43.506: IP-EIGRP(Default-IP-Routing-Table:10): Callback:
callbackup_routes 10.1.1.0/24
Corp(config-if)#n
*Mar 21 23:25:45.506: %LINK-5-CHANGED: Interface FastEthernet0/1, changed state
to administratively down
*Mar 21 23:25:46.506: %LINEPROTO-5-UPDOWN: Line protocol on Interface
FastEthernet0/1, changed state to down
Corp(config-if)#no shut
Corp(config-if)#^Z
*Mar 21 23:25:49.570: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state
to up
*Mar 21 23:25:49.570: IP-EIGRP(Default-IP-Routing-Table:10): Callback:
lostroute 10.1.1.0/24
*Mar 21 23:25:49.570: IP-EIGRP(Default-IP-Routing-Table:0): Callback: redist
connected (config change) FastEthernet0/1
*Mar 21 23:25:49.570: IP-EIGRP(Default-IP-Routing-Table:0): Callback: redist
connected (config change) Serial0/0/0
*Mar 21 23:25:49.570: IP-EIGRP(Default-IP-Routing-Table:0): Callback: redist
connected (config change) Serial0/0/1
*Mar 21 23:25:49.570: IP-EIGRP(Default-IP-Routing-Table:0): Callback: redist
connected (config change) Serial0/1/0
*Mar 21 23:25:49.570: IP-EIGRP(Default-IP-Routing-Table:0): Callback: redist
connected (config change) Serial0/2/0
*Mar 21 23:25:49.570: IP-EIGRP(Default-IP-Routing-Table:10): Callback: route_
adjust FastEthernet0/1
*Mar 21 23:25:50.570: %LINEPROTO-5-UPDOWN: Line protocol on Interface
FastEthernet0/1, changed state to up