Hi,
Recently I was studying EIGRP on a lab scenario and noticed a strange thing.
I connected three routers in a chain
R1---------R3--------R2
The connection between R1 and R3 is direcly connected ethernet with a cross cable while the connection between R3 and R2 is a serial connection.
The network between R1 and R3 is 192.168.1.0/30 and the network between R3 and R2 is 172.168.1.0/30 while the routers R1, R2 and R3 are configured with loopbacks 1.1.1.1, 2.2.2.2 and 3.3.3.3 respectively.
1) If I configure neighborship between R1 and R3(ethernet connection) by simply advertising networks by the network command the neighborship forms on the basis of multicast.
2) And if I configure neighborship between R3 and R2(Serial link) by advertising networks in the eigrp process the neighboship forms on multicast.
3) But when I check the output of "show ip eigrp interface details" I observe that the serial interface shows as to use unicast updates although I m not using the neighbor command.
R3#sh ip eigrp int det
IP-EIGRP interfaces for process 10
Xmit Queue Mean Pacing Time Multicast Pending
Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes
Et0/1 1 0/0 55 0/2 196 0
Hello interval is 5 sec
Next xmit serial <none>
Un/reliable mcasts: 0/5 Un/reliable ucasts: 11/5
Mcast exceptions: 1 CR packets: 1 ACKs suppressed: 0
Retransmissions sent: 1 Out-of-sequence rcvd: 0
Authentication mode is not set
Use multicast
Se1/0 1 0/0 74 0/15 335 0
Hello interval is 5 sec
Next xmit serial <none>
Un/reliable mcasts: 0/0 Un/reliable ucasts: 10/17
Mcast exceptions: 0 CR packets: 0 ACKs suppressed: 8
Retransmissions sent: 0 Out-of-sequence rcvd: 0
Authentication mode is not set
Use unicast
R3#
I did "debug ip packet detail" to verify this and observed that the updates on the serial are indeed sent to the multicast ip 224.0.0.10. Even if I ping 224.0.0.10 I do receive replies from the serial ip address of the neighbor router.
I m attaching the details of the router R3. Is this the correct behavior/output or m I missing some point?
Regards,
Talha
