Fa ports

Unanswered Question
Sep 12th, 2007

Can I have Fa 0/1 and Fa 0/0 on a 2801 router, assigned the same IP address and gateway?

I have this problem too.
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scottmac Wed, 09/12/2007 - 12:14

No. The router would not be able to create a routing / forwarding table with two interfaces configured the same way.

IOS would probably not even let you do it.

Richard Burts Wed, 09/12/2007 - 12:22


Scott is correct that the IOS will not let you configure 2 FastEthernet interfaces on the same router with the same IP address (or even 2 addresses in the same subnet). The closest that you could come to that would be to configure both interfaces with no ip address and to configure transparent bridging on the interfaces. You could then configure Integrated Routing and Bridging. In IRB you cnfigure bridgin on the LAN physical interfaces and then you configure a virtual interface (a BVI), you link the BVI to the bridge group on the interfaces, and you configure the IP address on the BVI.

You could do this, but I would not recommend it. If you can tell us what you are hoping to accomplish perhaps we can suggest some alternative that might work.



omgjames1 Wed, 09/12/2007 - 12:27

I have Blue Coat appliance, I installed a pass through card so that if the B/C dies we can still access the internet.

the pass through card has two ports on it, one goes to our switch and the other to the router to the Fa port. Any idea what the IP address of the Fa port should point to?

Kevin Dorrell Wed, 09/12/2007 - 12:21

Only if you bridge them.

bridge irb

bridge 1 protocol ieee

int f0/0

 bridge-group 1

int f0/1

 bridge-group 1

int bvi 1

 ip address [addr] [mask]

"... and gateway..." ... ?

Kevin Dorrell



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