CCNP ROUTE: 1. EIGRP Protocol messages

Displaying EIGRP protocol messages on R6:

The EIGRP packets are: HELLO, UPDATE, QUERY, REPLY, ACK

R6#show ip eigrp neighbors 
IP-EIGRP neighbors for process 1
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
2   172.16.0.10             Se0/1             12 01:13:21  145   870  0  3
1   172.16.0.2              Se0/0             10 01:13:24  186  1674  0  3
0   172.16.0.6              Fa0/1             13 01:13:24  757  4542  0  4

R6#debug eigrp packets
Normal operation:
*Mar  1 01:16:09.303: EIGRP: Sending HELLO on Serial0/1
*Mar  1 01:16:09.307:   AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
*Mar  1 01:16:09.759: EIGRP: Received HELLO on Serial0/1 nbr 172.16.0.10
*Mar  1 01:16:09.759:   AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0

*Mar  1 01:16:10.099: EIGRP: Sending HELLO on Serial0/0
*Mar  1 01:16:10.099:   AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
*Mar  1 01:16:10.243: EIGRP: Received HELLO on FastEthernet0/1 nbr 172.16.0.6
*Mar  1 01:16:10.243:   AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0

*Mar  1 01:16:11.167: EIGRP: Sending HELLO on FastEthernet0/1
*Mar  1 01:16:11.167:   AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
*Mar  1 01:16:11.655: EIGRP: Received HELLO on Serial0/0 nbr 172.16.0.2
*Mar  1 01:16:11.655:   AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0

Neighbor 172.16.0.10 (R7) goes down (after 15 seconds the Holdtime expires. Hello interval is 5 seconds. If the router does not receive a Hello from a neighbor for an entire Holdtime, then the neighbor is considered dead):
*Mar  1 01:16:44.027: EIGRP: Holdtime expired
*Mar  1 01:16:44.027: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 172.16.0.10 (Serial0/1) is down: holding time expired
*Mar  1 01:16:44.035: Going down: Peer 172.16.0.10 total=2 stub 0 template=2, iidb-stub=0 iid-all=0
*Mar  1 01:16:44.043: EIGRP: Neighbor 172.16.0.10 went down on Serial0/1

Neighbor 172.16.0.10 (R7) comes back up (as soon as a Hello is received from R7 on Serial0/1, the adjacency is formed again and Update/ACK messages are flowing between the routers in order to exchange topology data):
*Mar  1 01:36:05.367: EIGRP: Sending HELLO on Serial0/1
*Mar  1 01:36:05.371:   AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
*Mar  1 01:36:05.423: EIGRP: Received HELLO on Serial0/1 nbr 172.16.0.10
*Mar  1 01:36:05.423:   AS 1, Flags 0x0, Seq 0/0 idbQ 0/0
*Mar  1 01:36:05.427: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 172.16.0.10 (Serial0/1) is up: new adjacency
*Mar  1 01:36:05.431: EIGRP: Enqueueing UPDATE on Serial0/1 nbr 172.16.0.10 iidbQ un/rely 0/1 peerQ un/rely 0/0
*Mar  1 01:36:05.435: EIGRP: Received UPDATE on Serial0/1 nbr 172.16.0.10
*Mar  1 01:36:05.439:   AS 1, Flags 0x1, Seq 5/0 idbQ 0/0 iidbQ un/rely 0/1 peerQ un/rely 0/0
*Mar  1 01:36:05.443: EIGRP: Requeued unicast on Serial0/1
*Mar  1 01:36:05.443: EIGRP: Sending UPDATE on Serial0/1 nbr 172.16.0.10
*Mar  1 01:36:05.447:   AS 1, Flags 0x1, Seq 14/5 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1
*Mar  1 01:36:05.447: EIGRP: Enqueueing UPDATE on Serial0/1 iidbQ un/rely 0/1 serno 1-6
*Mar  1 01:36:05.447: EIGRP: Sending HELLO on Serial0/1
*Mar  1 01:36:05.447:   AS 1, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/1
*Mar  1 01:36:05.451: EIGRP: Enqueueing UPDATE on Serial0/1 nbr 172.16.0.10 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 1-6
*Mar  1 01:36:05.455: EIGRP: Received UPDATE on Serial0/1 nbr 172.16.0.10
*Mar  1 01:36:05.455:   AS 1, Flags 0x8, Seq 6/14 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2
*Mar  1 01:36:05.455: EIGRP: Enqueueing ACK on Serial0/1 nbr 172.16.0.10
*Mar  1 01:36:05.455:   Ack seq 6 iidbQ un/rely 0/1 peerQ un/rely 1/1
*Mar  1 01:36:05.459: EIGRP: Suppressed ACK 6 to 172.16.0.10 on Serial0/1
*Mar  1 01:36:05.463: EIGRP: Sending UPDATE on Serial0/1 nbr 172.16.0.10
*Mar  1 01:36:05.467:   AS 1, Flags 0x8, Seq 15/6 idbQ 0/0 iidbQ un/rely 0/1 peerQ un/rely 0/1 serno 1-6
*Mar  1 01:36:05.475: EIGRP: Requeued unicast on Serial0/1
*Mar  1 01:36:05.519: EIGRP: Received UPDATE on Serial0/1 nbr 172.16.0.10
*Mar  1 01:36:05.523:   AS 1, Flags 0x8, Seq 7/15 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2

This was a brief review of the EIGRP types of messages (except for QUERY and REPLY, which are covered in another lab exercise).