So I have a cisco 2811 router and 2 3560 switches
Currently the router is connected to Core1 only, what i would like to do is use the other port on the router (fa0/1) to connect to Core 2.
How do I go about doing this? The router currently has the ip 192.168.1.1 and Core 1: 192.168.1.251 Core 2: 192.168.1.252
I tried to make another interface on the router but it complained that the ip address that I set conflicted with the one of fa0/0 to Core 1
You need to enable IRB (integrated routing and bridging) on the two router ports. You create, in essence, a L2 bridge between them. You then put the IP address in the BVI (bridge virtual interface).
Be sure to enable spanning tree, as you are creating a second L2 path.
As router is layer3 devices .Hence each interface connected and configured with each networks .
In this scenario both core1 & core 2 switch are connected with two router interface with same networks ip address 192.168.1.X . That's the reason getting ip address conflict error while other router port configured .
To avoid this error configure another networks address to another router interfàce .
