Viewing EIGRP Packets

Viewing EIGRP Packets
Viewing the routing updates your router is sending and receiving is an invaluable tool. The following
debug commands will give you a step-by-step account of what is happening between
your router and its neighbors.
Dallas#debug ip eigrp
IP-EIGRP Route Events debugging is on
16:04:19: IP-EIGRP: 10.10.10.0/24 - do advertise out Serial2/0.1
16:04:19: IP-EIGRP: 192.168.24.0/24 - do advertise out Serial2/0.1
16:04:19: IP-EIGRP: Int 192.168.24.0/24 metric 128256 - 256 128000
16:04:19: IP-EIGRP: Processing incoming UPDATE packet
16:04:19: IP-EIGRP: Int 20.20.20.0/24 M 1889792 - 1249792 640000 SM 128256 -
➥256 128000
16:04:19: IP-EIGRP: Int 20.20.20.0/24 metric 1889792 - 1249792 640000
16:04:19: IP-EIGRP: Processing incoming UPDATE packet
16:04:19: IP-EIGRP: Int 192.168.24.0/24 M 4294967295 - 1657856 4294967295
➥SM 429 4967295 - 1657856 4294967295
The debug ip eigrp command allows you to view the routing updates sent between the
router and its neighbors. The information contained is the routes and their corresponding metric
the router has received along with what routes the router is going to send out and the interface
that will advertise the route. Recall that the value 4,294,967,295 represents infinity for
IGRP and EIGRP, thus an unreachable advertisement.
The debug eigrp packets command can be used to view the following types of packets
sent between the router and its neighbors:
 Hello
 Update
 Request
138 Chapter 4  IGRP and EIGRP
 Query
 Reply
The update and query messages are all considered reliable EIGRP messages.
This means that the receiving router must send back an acknowledgment to the
message.
Here’s an example of the output of the debug eigrp packets command:
Dallas#debug eigrp packets
EIGRP Packets debugging is on
(UPDATE, REQUEST, QUERY, REPLY, HELLO, IPXSAP, PROBE, ACK, STUB,
➥SIAQUERY, SIAREPLY)
Dallas#
16:07:43: EIGRP: Received HELLO on Serial2/0.1 nbr 10.10.10.1
16:07:43: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ
➥un/rely 0/0
16:07:43: EIGRP: Sending HELLO on Loopback0
16:07:43: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
16:07:43: EIGRP: Received HELLO on Loopback0 nbr 192.168.24.1
16:07:43: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0
16:07:43: EIGRP: Packet from ourselves ignored
16:07:44: EIGRP: Sending HELLO on Serial2/0.1
16:07:44: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
16:07:47: EIGRP: Received HELLO on Serial2/0.1 nbr 10.10.10.1
16:07:47: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ
➥un/rely 0/0
You can also view the number of EIGRP packets sent and received on the router. The show
ip eigrp traffic command displays the number of packets sent and received for each of these
packet types:
 Hello
 Update
 Query
 Reply
 ACKs
The next example shows the output for the show ip eigrp traffic command:
Dallas#show ip eigrp traffic
IP-EIGRP Traffic Statistics for process 100
Hellos sent/received: 632/622
Updates sent/received: 19/18
Summary 139
Queries sent/received: 0/0
Replies sent/received: 0/0
Acks sent/received: 8/11
There is one more command I’m going to explain. The show ip eigrp events command
is an undocumented command. This command displays a log of every EIGRP event—when
routes are injected and removed from the routing table and when EIGRP adjacencies reset or
fail. This information can be used to see if there are routing instabilities in the network. Here’s
an example of the output from this command:
Dallas#show ip eigrp events
Event information for AS 100:
1 16:14:45.007 Poison squashed: 192.168.24.0/24 reverse
2 16:14:44.967 Change queue emptied, entries: 1
3 16:14:44.967 Metric set: 20.20.20.0/24 1889792
4 16:14:44.967 Update reason, delay: new if 4294967295
5 16:14:44.967 Update sent, RD: 20.20.20.0/24 4294967295
6 16:14:44.967 Update reason, delay: metric chg 4294967295
7 16:14:44.967 Update sent, RD: 20.20.20.0/24 4294967295
8 16:14:44.967 Route install: 20.20.20.0/24 10.10.10.1
9 16:14:44.967 Find FS: 20.20.20.0/24 4294967295
10 16:14:44.967 Rcv update met/succmet: 1889792 128256
11 16:14:44.967 Rcv update dest/nh: 20.20.20.0/24 10.10.10.1
12 16:14:44.967 Metric set: 20.20.20.0/24 4294967295
13 16:14:42.059 Peer up: 10.10.10.1 Serial2/0.1
14 16:14:39.963 Peer down end, handle: 0
15 16:14:39.963 NDB delete: 20.20.20.0/24 1
16 16:14:39.963 Poison squashed: 20.20.20.0/24 rt gone
17 16:14:39.963 RDB delete: 20.20.20.0/24 10.10.10.1
18 16:14:39.963 Not active net/1=SH: 20.20.20.0/24 0
19 16:14:39.963 FC not sat Dmin/met: 4294967295 1889792
20 16:14:39.963 Find FS: 20.20.20.0/24 1889792
21 16:14:39.963 Peer down: 10.10.10.1 Serial2/0.1
As I stated at the beginning of this section, there are many tools available for verifying
and troubleshooting EIGRP. Remember, the tools covered here are not the only ones. I
know all this information can be overwhelming at first, but with time and practice it will
become second nature.