Ecapsulation Failed

[Thomas Yarger]

All,

I just installed two Cisco 3750X in our datacenter. I have 6 Dell EqualLogic SAN arrays attached to both switches in redundant fashion. Jumbo frames is not enabled but I do have flowcontrol turned on all switchports.The 3750X are stacked using StackWise Plus. When I execute sh ip traffic, I'm seeing;

IP statistics:

  Rcvd:  103669 total, 100274 local destination

         0 format errors, 0 checksum errors, 0 bad hop count

         0 unknown protocol, 3395 not a gateway

         0 security failures, 0 bad options, 343384 with options

  Opts:  0 end, 0 nop, 0 basic security, 0 loose source route

         0 timestamp, 0 extended security, 0 record route

         0 stream ID, 0 strict source route, 343384 alert, 0 cipso, 0 ump

         0 other

  Frags: 0 reassembled, 0 timeouts, 0 couldn't reassemble

         0 fragmented, 0 couldn't fragment

  Bcast: 0 received, 0 sent

  Mcast: 0 received, 0 sent

  Sent:  103543 generated, 0 forwarded

  Drop:  203 encapsulation failed, 0 unresolved, 0 no adjacency

         0 no route, 0 unicast RPF, 0 forced drop

         0 options denied, 0 source IP address zero

What does encapsulation failed mean? Thanks

[Sandeep Choudhary · Accepted solution]

Hi Thomas,

Encapsulation failure happens when the router can't resolve a IP to a mac address..

So hhen you see encapsulation failed counter increasing it would most likely be because the router did not receive arp replie to some arp requests, so the packets were discarded.

What is the ios version of the Switch.

Earlier , The bug was identified in Cisco IOS Software Release 12.1(14)EA1a and is fixed on Cisco IOS Software Releases 12.2(25)SEA and later.

The permanent solution is to upgrade to the latest Cisco IOS version. The temporary workaround is to disable IGMP snooping on the Catalyst 3750 stack, or disable MAC-based query on the switch connected to the 3750 stack.

Regards

Please rate if it helps.