Cisco Router – Multiple Interfaces in the Same Broadcast Domain

ciscolayer3routing

I have a Cisco 3945E with two EtherSwitch modules (gi 1/0, gi 2/0) and a UCSE (ucse 4/0) server installed in it.

The short of it is i'd like to trunk VLANs to the two EtherSwitch modules, and place the UCSE's IMC on a server VLAN:

VLAN 08 - SERVER: 10.2.8.1/24  - Trunked to EtherSwitches, untagged to UCSE 4/0.
VLAN 16 - VOICE:  10.2.16.1/24 - Trunked to EtherSwitches
VLAN 24 - DATA:   10.2.24.1/24 - Trunked to EtherSwitches

I'm familiar with configuring a router on a stick, but totally lost as to how to assign the same broadcast domain (and IP address) to multiple interfaces on a router.

EDIT:

I've been able to use BVIs to span the broadcast domain to two of the router's ports, but UCSE is still giving me trouble:

interface GigabitEthernet0/0
 no ip address
 duplex auto
 speed auto
interface GigabitEthernet0/0.8
 encapsulation dot1Q 8 native
 bridge-group 8
interface ucse4/0
 ip unnumbered BVI8
 imc ip address 10.2.8.2 255.255.255.0 default-gateway 10.2.8.1 
interface BVI8
 ip address 10.2.8.1 255.255.255.0

I have a device on gi 0/0 with ip 10.2.8.3/24 and can ping it with no issues, but the IMC still cannot be reached. I've tried creating host routes from 10.2.8.2 to bvi 8 and/or ucse 4/0 to no luck…

Any help is appreciated!

Best Answer

The configuration in the original post was close, but was missing a few key things:

interface ucse4/0
  ip unnumbered BVI8
  imc ip address 10.2.8.2 255.255.255.0 default-gateway 10.2.8.1 
  imc access-port shared-lom console

ip route 10.2.8.2 255.255.255.255 ucse 4/0

Note the imc access-port shared-lom console. It was the only way I could manage to get the IMC address pingable. I should also point out that by default, the BVI will not bring itself up unless there is another active port bridged to it.