Thursday, April 13, 2017

Put Several Router Interfaces in Same Subnet (BVI Configuration of IOS)

For some network designs, you may need to put 2 or more interfaces on a same router to operate in one subnet. Example situations are redundant high availability links, ip saving (point-to-point links) etc.. You can do this by creating a BVI (Bridge Virtual Interface) in IOS..

VLAN 10 is created in both SW1 & SW2 as the subnet of 192.168.10.0/24 & the interface IPs of SW1 & SW2 for VLAN 10 are 192.168.10.1 & 192.168.10.2 respectively..

VLAN 10 is allowed in the trunk links in between 2 switches and e0/0 port of both switches are access ports for VLAN 10..


Now let's move on with R1's configuration..



1. Enable Integrated Routing & Bridging
R1(config)#bridge irb

2. Specify Spanning Tree Protocol for this BVI
R1(config)#bridge 10 protocol ieee

10 is the BVI number..

3. Specify Protocol to be Routed in this BVI
R1(config)#bridge 10 route ip

4. Configure IP for this BVI
R1(config)#int bvi 10
R1(config-if)#ip address 192.168.10.3 255.255.255.0

When you give an IP to the BVI, it will create a MAC address for that and put it in ARP table..









5. Assign Physical Ports to the BVI
R1(config)#int e0/0
R1(config-if)#bridge-group 10

R1(config)#int e0/1
R1(config-if)#bridge-group 10

BVI configuration is now over.. Even though R1's e0/0 port fails switches can access the router interface from R1's e0/1 port via the same IP..

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