G'day All,
I've got an issue with a new 4321 that is meant to be replacing a 2800 router that is acting as a voice gateway. The 2800 uses a BVI to connect 2 gig interfaces to two 6509 switches and this works a treat at the moment. STP is blocking the vlan on one of the switch interfaces to the router, while the other forwards, as expected.
The new 4321 was built, but the BVI config is not able to be used, so based on the Cisco doco, the Bridge Domain setup was used, which I have posted below. On paper the config looked good and the router was introduced into the network. Cue spanning tree loop and network outage. Luckily this was afterhours so no real harm done.
So my understanding was that in the new IOS XE software, the BDI replaced the BVI, but this didn't work as I had expected. When using the BDI configuration on the router, the downstream switch ports didn't do any blocking of the vlan to the router and both switch ports stayed as forwarding.
Enabling BPDU guard, works as expected with one of the switch ports going err-disable after seeing an unexpected BPDU, but without that, at no point does either switchport block the vlan to prevent the loop. The switch ports configuration didn't change between the old 2800 and the new 4321 going in.
It is a pretty basic setup and it was that was inherited from the previous network guys, so I am wondering if anyone out there has any experience with BDIs and connecting to switches.
I've attached a basic diagram with some config of both the old and new router (the important bits).
Cheers,
JS
