Stacked 3750g routing failover

[josephp]

Hi Folks,

Hope all is well. I have a stacked 3750g's that are peering with 2 ISP running BGP (multi-homed). 1 isp is pluged directly on a port on the stack master and the other isp is on a member for redundancy. I also have a 3925 that have 4 connections to the the stacked (2 ports on each switch on the stack) that I use as a back connection peering OSPF with the 3750g.

I need a little help in understanding how the failover happens on a Stacked 3750g. If the stack master fails, does the routing process drop during the election and then re-establish the peering?

Thank you in advanced I appreciate any help.

Best Regards,

JP

[Reza Sharifi]

Hi Joe,

From the StackWise document notes that:

When one master switch becomes inactive and while a new master is elected, the stack continues to function. Layer 2 connectivity continues unaffected. The new master uses its hot standby unicast table to continue processing unicast traffic. Multicast tables and routing tables are flushed and reloaded to avoid loops. Layer 3 resiliency is protected with NSF, which gracefully and rapidly transitions Layer 3 forwarding from the old to new master node.

So, it seems that your routes get flushed and repububilted in a case when the master goes inactive

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps5023/prod_white_paper09186a00801b096a.html

HTH

Reza