Core issue
The redundant Route Processors (RPs) have different memory configurations. To support the high availability feature, it is recommended that both RPs have the same memory configurations.
This issue is specific to MSFC2. It is not neccessary that the error message and the duplicate interface always occur together. If the ROM Monitor (ROMmon) version is not the minimum required to support the Cisco IOS for MSFC2, this causes the error message to be displayed, even if the memory configurations are physically correct between both RPs. This issue can also lead to duplicate or bogus Switched Virtual Interfaces (SVIs) or interface VLANs.
This is an example:
router#show running-config
!
interface Vlan24
ip address 10.24.24.254 255.255.255.0
ip helper-address 10.24.2.245
no ip redirects
!
interface Vlan24
no ip address
shutdown
!
router#show ip interface brief
Interface IP-Address OK? Method Status Protocol
Vlan24 10.24.24.254 YES manual up up
Vlan24 unassigned YES unset administratively down down
Resolution
To resolve the issue, perform these steps:
Install the same amount of memory on both RPs.
Ensure that the minimum ROMmon version is installed on the route processor according to the Cisco IOS version that is running on it. If not, upgrade the ROMmon by referring to the Upgrading the MSFC2 ROMMON section of Catalyst 6000 and Cisco 7600 MSFC2 ROMMON Software.
This should fix the duplicate interface VLAN issue as well. If the problem persists, contact Cisco Technical Support.