Point to Point Configuration Question

Answered Question
Jun 18th, 2007

Hello:

I have an existing 2 T bundle terminating into our 3660. I have to bring in another single T1 for a point to point connection to a remote office. A question about routing.

I already have a statement 0.0.0.0 0.0.0.0 214.x.x.x to handle routing out for the 2 T bundle. How do I differentiate the point point traffic on the new T to route out it's serial instead of the 2 T serial?

Thanks

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Correct Answer by Richard Burts about 9 years 5 months ago

Joe

Yes, if the LAN at the remote office uses addresses in 192.168.1.0/24 and if the serial interface that connects to that office is serial 3/0 then you could configure ip route 192.168.1.0 255.255.255.0 serial 3/0.

This would allow the existing T1 bundle to continue to route to the Internet and would allow the new T1 to independently route traffic to the remote office over the new T1.

HTH

Rick

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mohammedmahmoud Mon, 06/18/2007 - 04:39

Hi,

If you need certain traffic to go through the new link other than the traffic using the default route over the 2T bundle, you'll have to use PBR (Policy Based Routing).

Policy-Based Routing

http://www.cisco.com/warp/public/732/Tech/plicy_wp.htm

Configuring Policy-Based Routing

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos_c/fqcprt1/qcfpbr.htm

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

Richard Burts Mon, 06/18/2007 - 04:48

Mohammed

My understanding of the original post is a bit different than yours. The original post shows a static default route using the bundle and then it says:

"another single T1 for a point to point connection to a remote office"

I believe that the default route out the bundle is still valid and that since the remote office will have a unique set of destination addresses all that is needed is a new static route pointing the new destination addresses out the new serial. Assuming that the network at the remote office was 192.168.10.0/24 and that the new T1 was serial 2/0 then the static route would look like this: ip route 192.168.10.0 255.255.255.0 serial 2/0

Policy Based Routing is effective if you need to make routing decision based on the source address (where did it come from) but in this case I believe that the routing decision is still based on destination address (where is it going) and that a simple static route is sufficient.

HTH

Rick

mohammedmahmoud Mon, 06/18/2007 - 05:18

Hi Rick,

You are completely right if the first bundle is not going to the same remote office (and after a through reading for the original poster's post i think that you are right). Joe, please do accept my apologies for any inconvenience, Rick, thanks for having you around :)

As Rick have stated its a matter of static routes for the IPs on both sides (more specific IPs rather than the default route), and please do make sure that the static routes are configured right on both sides.

BR,

Mohammed Mahmoud.

js358 Mon, 06/18/2007 - 06:42

Rick - Thanks. The T1 bundle routes out with default 0.0.0.0 0.0.0.0 214.x.x.x

The other T1 will route to the remote office. I will have to leave the default route up for the bundle since they route out to the internet and not a specific IP range.

Seems I would need source based or can I just designate a static route for the T1 going to remote office ?

Thanks

Richard Burts Mon, 06/18/2007 - 08:15

Joe

Why would you think that you need source based routing? Unless there is something that I have seriously misunderstood a simple static route should do just fine.

Please correct me if my understanding is incorrect, but you currently have a static default route using the T1 bundle and will be bringing up a new T1 to a remote office. The remote office will have some set of IP addresses that you need to access. Why wold you not just configure a static route that has the addresses of the new remote as the destination and the serial interface (or the next hop address of the remote office) as the way to get there?

HTH

Rick

js358 Mon, 06/18/2007 - 09:47

Rick - I'm not that experienced with Cisco Routers - inherited this from the previous guy who left the company, so I'm not sure exactly what I need.

What I am concluding from your advice is that I can leave the default route in place which will take care of my 2 T bundle going out and place a static map in place for the T to my branch office?

So if their IP scheme was 192.16.1.0/24, I could insert a static map something like ip route 192.168.1.0/24 ser3/0?

Thanks for your help with this.

Correct Answer
Richard Burts Mon, 06/18/2007 - 10:24

Joe

Yes, if the LAN at the remote office uses addresses in 192.168.1.0/24 and if the serial interface that connects to that office is serial 3/0 then you could configure ip route 192.168.1.0 255.255.255.0 serial 3/0.

This would allow the existing T1 bundle to continue to route to the Internet and would allow the new T1 to independently route traffic to the remote office over the new T1.

HTH

Rick

js358 Mon, 06/18/2007 - 10:26

Thanks Rick - you've been a big help. I was just a little concerned and didn't want to affect the existing traffic on this router.

Thanks Again.

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