[c-nsp] Duplicate IP add on CAt6509

[Dave Lim]

Anyone have faced this log message of duplicate IP address before?

Here is the network topology

C6509CS01 --------------- C6509CS02
---------------

This problem occured for 5 min and brought the customer vlan 1 network. Note
that the

C6509CS01
Feb 8 08:08:32: %STANDBY-3-DUPADDR: Duplicate address 10.1.1.253 on Vlan1,
sourced by 0000.0c07.ac09

VLAN 1 MAC address on C6509CS01
Vlan1 is up, line protocol is up
Hardware is Cat6k RP Virtual Ethernet, address is 0009.b63e.cffc (bia
0009.b63

C6509CS02
*Feb 9 01:29:49: %STANDBY-3-DUPADDR: Duplicate address 10.1.1.252 on Vlan1,
sourced by 0009.b63e.bffc

VLAN 1 MAC address on C6509CS02
Vlan1 is up, line protocol is up
Hardware is Cat6k RP Virtual Ethernet, address is 0009.b63e.bffc (bia
0009.b63e.bffc)
Internet address is 10.1.1.252/24

I am suspecting this is a spanning tree loop and causes the switch to see a
duplicate IP address. But logically, there is no loop between the 2 6509
unless the port-channel connecting the 2 switches fail and in turns there is
a loop. But in this cases, STP should kick in.