Using a router to switch

[joeb]

PROBLEM

How to configure a router such that the router can direct traffic to an output interface solely based on layer 1 or layer 2 connectivity of the interface.

i.e Router has two output interfaces fa 0/0 and fa 0/1. When interface fa 0/0 is not connected traffic has to be directed to fa 0/1 which is obviously on a different subnet. The catch is that no routing protocols or redundancy protocols can be employed. The Router has to react purely on layer 1 and 2 connectivity. Which ever interface happens to be connected is the interface that traffic is directed. Also, CDP cannot be employed.

thanks

[aclman]

Any Cisco router can be configured as a bridge (with multiple segments). Here is a URL describing some of the bridging features of some (older) model routing switches.

http://www.cisco.com/en/US/docs/switches/lan/catalyst2948gand4908g/12.0_10_w5_18e/configuration/guide/bridging.html

The Nam-Kee books on bridging may be helpful to you on this topic. I used to have an old book that went through all the bridging options for Ethernet and token-ring, but I don't see it in print. I do see this book, which should provide similar examples of various bridging configurations.

http://www.bookfinder.com/dir/i/Configuring_Cisco_Routers_for_Bridging,_Dlsw,_and_ Desktop_Protocols/0071354573/

[aclman]

as you have asked before.... you would use track command in the global config. You can track layer1/2 or 3 of the interface. if the interface cannot send i.e. ospf than the link will not be used....