Why Can’t Ping Multicast Address 224.0.0.9 of RIP – Routing Insights

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We know that RIP v2 uses multicast address 224.0.0.9 for periodic broadcast of routing table. So it means that every router configured with RIP V2 is monitoring for any packet with destination address of 224.0.0.9.

So now if I ping that ip address; since router si listening to that ip, I should get a reply. But when I tested it on both GNS3 and Packet Tracer, no reply came.

I would like to know what is the reason.

Thank you in advance.

Best Answer

Damon, I'm afraid there is something wrong with your specific implementation. I, personally, can't think of an instance where a router doesn't respond to an icmp request on any of it's interfaces. Others, please chime in if that's inaccurate.

At any rate, I mocked it up in GNS3 to make sure there weren't any funky software bugs.

GNS3 Network Diagram

Basic configurations were set up on the interfaces with each router having it's router number as the lo0 interface address (i.e. R1 - 1.1.1.1). For verification, here's the rip routing table.

R1#show ip route rip
     2.0.0.0/32 is subnetted, 1 subnets
R       2.2.2.2 [120/1] via 10.1.1.2, 00:00:07, FastEthernet0/0
     3.0.0.0/32 is subnetted, 1 subnets
R       3.3.3.3 [120/1] via 10.3.3.3, 00:00:26, FastEthernet0/1
     10.0.0.0/24 is subnetted, 3 subnets
R       10.2.2.0 [120/1] via 10.3.3.3, 00:00:26, FastEthernet0/1
                 [120/1] via 10.1.1.2, 00:00:07, FastEthernet0/0
R1#

When pinging the multicast address of 224.0.0.9, 3 replys came back; R2 sent a reply, R3 sent a reply, and R1 replied to itself because it is also listening for that address.

R1#debug ip icmp
ICMP packet debugging is on
R1#ping 224.0.0.9 source lo0 repeat 1

Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 224.0.0.9, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1

*Mar  1 00:15:41.163: ICMP: echo reply sent, src 1.1.1.1, dst 1.1.1.1
*Mar  1 00:15:41.163: ICMP: echo reply rcvd, src 1.1.1.1, dst 1.1.1.1   <--- R1 Response
*Mar  1 00:15:41.179: ICMP: echo reply rcvd, src 10.1.1.2, dst 1.1.1.1  <--- R2 Response
*Mar  1 00:15:41.179: ICMP: echo reply rcvd, src 10.3.3.3, dst 1.1.1.1  <--- R3 Response
Reply to request 0 from 1.1.1.1, 8 ms
Reply to request 0 from 10.3.3.3, 24 ms
Reply to request 0 from 10.1.1.2, 20 ms
R1#

Pinging a multicast address will generate a response from participants listening to that address.

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