You need to change the router Ethernet interfaces from Routing mode, into Bridging mode, which means you cannot put an IP address on that interface. If you need an IP address from that segment on each Router, then create a BVI with the IP address and add the BVI to the same bridge group.
This is all from memory, however - 1. In global configuration mode, define the bridging method (probably integrated routing and bridging) - bridge irb 2. In global configuration mode, define a bridge group (7) for IEEE traffic (assuming your bridging needs are fairly standard) - bridge 7 protocol ieee 3. Put the desired interface into the bridge group - int e0 bridge-group 7 ??? Optionally add any specific bridging parameters if required.