I have one switch and two routers connected to this switch. HSRP is configured on both the lan interfaces of the routers.
Tracking is configured on the lan interfaces to track each serial link connected to each router to remote networks.My PC
is configured with the virtual HSRP IP as its default gateway.
When the active router or it's connected serial fails, the standby router takes up the active role and continue
to send all my lan traffic through it. My doubt is how the virtual HSRP mac address in the switch's mac address table is
mapped to the correct exit port(port connected to the now active router) which earlier mapped to a different port(port
connected to the now failed router) as HSRP hellos are exchanged only between the routers and not to the switch. I
understand that mac address table enteries are learnt from source mac addresses of incoming frames.
Could someone explain me the process of mac address table population of the switch during HSRP failover.
The active HSRP router is responsible for all the quries sent to the virtual Mac-address.
When the standby takes over as the active HSRP router, it starts responding to the virtual mac-address queries.
This mac-address is now learnt by the switch on the port which was conencted to the standby HSRP router and hence updates its CAM tabe accordingly.
eg. R1 & R2 are 2 routers running HSRP (gr#2). R1 connected to port1 & R2 to port2.
So the HSRP mac-address 0000.0c07.ac02 will be learnt at port1 by the switch. during failover this same address is learnt on port2 as R2 takes over the HSRP active role
HTH, rate if it does