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TrueDuality
Asked: 2010-08-10 09:46:36 +0800 CST

Simple point to point Cisco Router config for a T1

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We recently started leasing a small new site and part of the agreement was to have the owner of the building provide a point to point link between our main site and this building and we would purchase configure and maintain the hardware. The job fell on me to configure the two routers (1841s with CSU/DSU cards).

I unfortunately am not very Cisco savvy and I'm hoping to find some help here. I'm hoping to configure the two routers to essentially work like a standard ethernet cable. They need to be on the same subnet as one of our other departments (not NAT'd). The only examples I can find online involve both ends of the router being on separate subnets.

On our main site I have a port ready with the subnet I need. Can anyone out there provide me with some help?

router cisco t1

1 Answers

  1. Best Answer

    The terminology you're looking for is "bridging" when you say "essentially work like a standard ethernet cable". Beware that briding Ethernet over a slow WAN link may result in unacceptable utilization of the WAN link with broadcast traffic. That's why we typically route traffic across slow WAN links because, by default, routers don't forward broadcast traffic.

    You want something like:

    interface Serial 0
 bridge-group 1
 no ip address

interface FastEthernet 0
 bridge-group 1
 no ip address

interface BVI1
 ip address x.x.x.x y.y.y.y

ip route 0.0.0.0 0.0.0.0 z.z.z.z

    On those 1841's the "Serial 0" and "FastEthernet 0" interfaces might have slightly different names, but that's the gist of it.

    Replaced "x.x.x.x" with an IP address on your subnet, "y.y.y.y" with the subnet mask for that subnet, and "z.z.z.z" with the default gateway for that subnet. You'll want to use a different "x.x.x.x" address for the remote end.

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