Nexus 5500 duplicate ICMP echo-replay

[jsluzewski]

I am experiencing inconsistent echo-replay from devices connected via VPC to Nexus 5500s while pinging from the Nexus exec prompt.

In some cases I receive normal response when pinging from one Nexus,  but no response when pinging from the other switch. In other instance I receive normal response to one Nexus, and duplicate replays to the other. It looks like a VPC related bug. NXOS is 5.1.3.N2.1

5501# ping 10.12.12.232

PING 10.12.12.232 (10.12.12.232): 56 data bytes

64 bytes from 10.12.12.232: icmp_seq=0 ttl=253 time=8.585 ms

64 bytes from 10.12.12.232: icmp_seq=0 ttl=254 time=9.227 ms (DUP!)

64 bytes from 10.12.12.232: icmp_seq=1 ttl=253 time=1.011 ms

64 bytes from 10.12.12.232: icmp_seq=2 ttl=253 time=8.097 ms

64 bytes from 10.12.12.232: icmp_seq=2 ttl=254 time=9.429 ms (DUP!)

64 bytes from 10.12.12.232: icmp_seq=3 ttl=253 time=18.195 ms

64 bytes from 10.12.12.232: icmp_seq=4 ttl=253 time=8.807 ms

5502# ping 10.12.12.232

PING 10.12.12.232 (10.12.12.232): 56 data bytes

64 bytes from 10.12.12.232: icmp_seq=0 ttl=254 time=0.985 ms

64 bytes from 10.12.12.232: icmp_seq=1 ttl=254 time=0.884 ms

64 bytes from 10.12.12.232: icmp_seq=2 ttl=254 time=0.875 ms

64 bytes from 10.12.12.232: icmp_seq=3 ttl=254 time=3.105 ms

64 bytes from 10.12.12.232: icmp_seq=4 ttl=254 time=8.378 ms

Thanks

Jarek

[Reza Sharifi]

Check your equipment and configuration. Make sure the server NICs are configured correctly and on the switches and routers your IP segments have the correct masks with no loop in the network.

http://news-posts.aplawrence.com/2083.html

HTH

[jsluzewski]

I think it is really VPC related. The responding device is a Catalyst 2960 connnected to both Nexus via VPC.

[Jerry Ye]

Who is your L3? Is that another Nexus? If yes, I am going to assume you have "peer-gateway", if yes, then you need to make sure you have "no ip redirect" configured.

HTH,

jerry

[jsluzewski]

Disabling the ICMP redirect helped.

Thank you.

[ausjustin]

Hi Jsluzewski

I had same issue like yours one ... so what's command for disabling the ICMP ON 5k ？

Actually we had problem on N7K , but I think should be same as 5K .

no ip redirects

command on the interface.

is it correct  ?

[dresabala]

I had that same issue today and it was fixed with no ip redirect command.  Thank you.

[j-mccarthy]

Hi

I found this in the configuration guide for the Nexus 7000 configuring VPCs

"When you enable this feature (peer-gateway), Cisco NX-OS automatically disables IP redirects on all interface VLANs mapped over a vPC VLAN to avoid generation of IP redirect messages for packets switched through the peer gateway router."

However this is not happening automatically on the 5K, so you need to manually add "no ip redirects" on each VPC vlan interface to prevent duplicate pings.