[c-nsp] SUP2T Ignoring ARP response... 12.2(50)SY3

Peter Kranz pkranz at unwiredltd.com
Thu Apr 4 12:49:15 EDT 2013

A bit stumped by this one, perhaps someone has seen this behavior:

A particular MAC address is seen in two different VLANS: (Should be ok, MAC
address table is by VLAN right)

rtr-sungard#sho mac address-table | inc 0025.90a6.7ca2
       10 0025.90a6.7ca2  dynamic  Yes        5     Te5/5
*      11 0025.90a6.7ca2  dynamic  Yes       60     Te6/5

ARP table shows Incomplete ARP response for one of the VLANs:

Internet  x.x.x.x           0   Incomplete      ARPA   
Internet  x.x.x.x 1   0025.90a6.7ca2  ARPA   Vlan10

Cannot ping the host in Vlan11 as a result..

However packet captures from the host show the ARP response being sent as
desired on the Incomplete VLAN..

If the host Vlan11 pings the gateway on the 6500, ARP table is now populated
and pings possible..

Internet  x.x.x.x           0   0025.90a6.7ca2  ARPA   Vlan11
Internet  x.x.x.x           8   0025.90a6.7ca2  ARPA   Vlan10

Any ideas?

Peter Kranz
Unwired Ltd
pkranz at unwiredltd.com

More information about the cisco-nsp mailing list