I have a problem with VRRP or maybe spanning tree, I'm not sure yet and need some input.
My two 1921 routers are connected to a 3750-E stack of two switches where the different routers are connected with two trunk interfaces to one switch each. Both physical interface on the routers are configured with sub interfaces having separate VRRP groups. The attached image is a quick illustration of the setup.
A few times every hour I get log entries on Router2 saying it has become VRRP master of all VRRP groups and then a few seconds later VRRP backup again. I understand it would be a STP problem if the routers where physically distant with trunks between them but they are in the stame switch stack. The 3750 stack does however log MACFLAP_NOTIF on the VRRP MAC addresses when the flapping occurs.
Below is an example of the interface config on most of the flapping interfaces. Any ideas?
interface GigabitEthernet0/1.404 description DMZ encapsulation dot1Q 404 ip address 192.168.34.1 255.255.255.0 ip flow ingress ip flow egress ip virtual-reassembly in vrrp 34 ip 192.168.34.1
interface GigabitEthernet0/1.404 description DMZ encapsulation dot1Q 404 ip address 192.168.34.2 255.255.255.0 ip access-group DMZ in ip flow ingress ip flow egress vrrp 34 ip 192.168.34.1
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