If GLBP tracks an interface, and the priority changes because an interface goes down, the secondary router takes over as AVF, but it doesn't take over the active state of all the MAC addresses unless the other router goes away. This means that one router must rcv half of the traffic, but sends it out the same port so it can go out the other router.
I've done some testing by manually setting the priorities, these are the results -
Router1#sh run int fast 0/0
interface FastEthernet0/0
ip address 10.158.56.3 255.255.255.128
glbp 1 ip 10.158.56.1
glbp 1 preempt
Router1#sh glbp b
Interface Grp Fwd Pri State Address Active router Standby router
Fa0/0 1 - 100 Active 10.158.56.1 local 10.158.56.2
Fa0/0 1 1 7 Listen 0007.b400.0101 10.158.56.2 -
Fa0/0 1 2 7 Active 0007.b400.0102 local -
Router2#sh run int fast 0/0
interface FastEthernet0/0
ip address 10.158.56.2 255.255.255.128
glbp 1 ip 10.158.56.1
glbp 1 priority 50
Router2#sh glbp b
Interface Grp Fwd Pri State Address Active router Standby route
Fa0/0 1 - 50 Standby 10.158.56.1 10.158.56.3 local
Fa0/0 1 1 7 Active 0007.b400.0101 local -
Fa0/0 1 2 7 Listen 0007.b400.0102 10.158.56.3 -
By my interpretation, the router with the 100 priority should be the Active router for all MACs.
Any help on this would be appreciated.
