Well you can do it if you are bridging... Michelle Truman CCIE # 8098 Principal Technical Consultant AT&T Solutions Center 651-998-0949 mtruman@att.com -----Original Message----- From: Leo Bicknell [mailto:bicknell@ufp.org] Sent: Tuesday, November 11, 2003 8:56 AM To: nanog@trapdoor.merit.edu Subject: Re: Router with 2 (or more) interfaces in same network In a message written on Tue, Nov 11, 2003 at 08:35:34AM +0000, Sugar, Sylvia wrote:

I am curious to know if its possible to have a router with its two interfaces, say configured as, 1.1.1.1/16 and 1.1.1.2/16. Theoretically, i see nothing which can stop a router from doing this.

Cisco's don't let you do this. I have always considered that broken, although I'm sure Cisco thinks it's a feature. Other routers (of note FreeBSD boxes) do this just fine. In almost all cases I've seen it done it was for more bandwidth to the box (typically inbound only, because there are no good tools on Unix boxes to split the traffic between the outgoing interfaces). I've seen it done a lot in labs where you have something like this: client 1 | | client 5 client 2 +----B----+ client 6 client 3 | | client 7 client 4 | | client 8 | | file-server-router-box | Internet Where all the clients are in one subnet, there are two interfaces, and the networks are separated (today the left and right groups on two different switches, I drew the old school picture of thinwire with a bridge in the middle. While this will work (with some boxes, again Cisco's won't let you configure the same subnet on two interfaces), it is at best a hack that helps in some specific instances. It is quite clearly not good network design. Maybe they have one of those specific instances but I'd get a lot more detail and be sure before you offer up this hack as otherwise you've got a messy config that didn't do what the customer wanted anyway. -- Leo Bicknell - bicknell@ufp.org - CCIE 3440 PGP keys at http://www.ufp.org/~bicknell/ Read TMBG List - tmbg-list-request@tmbg.org, www.tmbg.org