sh standby vlan 23

Vlan23 - Group 18

  Local state is Active, priority 110

  Hellotime 3 holdtime 10

  Next hello sent in 00:00:00.036

  Virtual IP address is 10.2.221.35 configured

  Active router is local

  Standby router is 10.2.221.33 expired

  Standby virtual mac address is 0000.0c07.ac12

  11 state changes, last state change 00:00:08

I don't know your topology but on Vlan23 you have flaps ongoing:

11 state changes, last state change 00:00:08

I believe at some point both parts that form the HSRP for VLAN23 lose the connection one to each other, and each of them thinks that it is the active one. If you have multiple trunks between this 2 devices, or a topology in which you can run into loops (like a square topology) than you encounter this error.

Human speaking, if both routers think that they are the Active part on HSRP, and in between you have a trunk (or a loop) transporting VLAN 23, then is normal that one router will say, hey there is another router on this segment who's using 10.2.221.35 (even if this address is virtual).

My advice is to check why HSRP on vlan 23 is flapping. Check logs, check if there are flappings on the physical interface that is transporting this vlan23.

Check with sh standby vlan 23 which router is active. If both of them are active...there is your problem. See if you can ping on the vlan23 from one router to the other one.

Let me know how this works for you!

Hello Advait,

as Calin has noted you probably are facing stability issues in vlan 23.

In this case the message is more an indication of underlying problems at OSI layer2 rather then a problem.

This kind of messages appear at the beginning of a broadcast storm caused by a spanning-tree loop

Hope to help

Giuseppe

This is making some sense now.

I have got 2 MSFC, I have shutdown vlan 23 on MSFC on which I was receiving Duplicate address error. After that there is no vlan flap logs on both MSFC. Before that I was receiving Vlan Flapping Errors on all vlans.

if I enabled vlan 23 on MSFC again I will start receiving same error. Please let me know how can I solve this problem.

There is no physical port flapping errors.

when I am checking sh standby brief

The vlan 23 state is showing active on both MSFC.

Hello Advait,

two MSFCs

are the two MSFCs in the same C6500 chassis and you are running in dual routing mode DRM or single routing mode?

if the two MSFCs are in different chassis you need to check the path between them for vlan 23: if both claim to be active it means that HSRP hello messages sent to 224.0.0.2 are not received by the other MSFC and viceversa and this means that vlan23 is partititioned in some place.

to be noted that if both MSFCs are in the same chassis the use of HSRP may be not appropriate, this depends on the routing engine redundancy mode.

In DRM both MSFCs are active and each needs to have its own IP addresses on the different Vlans, different IP addresses for loopbacks and so on.

External world knows there are two routing engines.

DRM is not recommended and the recent way to use two MSFCs in same chassis is Single Router Mode: in this case there is a standby MSFC that is isolated from outside world, outside world never knows there two MSFCs in the box only one speaks.

Hope to help

Giuseppe

Both MSFC are in different Core on Different Location.

Please check the attached file.

You have there HA configured? If yes, what method for the HA?

After changing standby group I am not getting error on MSFC.