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New Member

Point-to-Point T1

I have a very simple project which for some reason is becoming very difficult (probably because I don't know what I am doing), but anyway. We just leased a point-to-point T1 and have a Cisco 2600 on both ends. All that I want to do is have the network on the far end of the T1 think that it is part of our network. I.E. I simply want the two routers to act like bridges and connect the remote end so that it can register with our dhcp server and use our internet connection. We have have a small network so there are no access-lists or tricky security considerations. We are using an internal class b addressing scheme for the network, again nothing tricky. If you could give me some basic configuration suggestions I would really appreciate it.

  • Other Network Infrastructure Subjects
New Member

Re: Point-to-Point T1


Without knowing what problems you're running into, it's tough to know what's difficult. I'll just spout some stuff off and hope it helps ... :)

UDP broadcasts are used to locate network services such as NT Domain Controllers, DHCP, DNS, and BOOTP. However, routers do not forward UDP broadcasts by default. In order to provide access to these services across the WAN, each remote Ethernet port on the router may require an IP Helper address to forward UDP broadcasts to the appropriate server.

Make sure your subnet masks are correct. Can you ping both router interfaces from the local subnets? If you can, then we can look at the T1 setup.

Try these and let me know if it works.

Steve Olson

New Member

Re: Point-to-Point T1

The actual problem that I'm having is that yes I can ping from the remote client to the server and if I manually give the remote machines an IP address they can login without any problems. However, if I set them to automatically obtain a ip lease from the dhcp server they are unable to find it. I tried putting the IP helper address in and it didn't seem to help. And no I'm not sure that the subnet masks are correct and would appreciate any advice. Our dhcp server address is and I have the range of through reserved for equipment. If you don't mind, could you give me sample of how you would do it, including subnet masks. Also the rest of our network, because it is small, is using RIP. Is this a problem?

New Member

Re: Point-to-Point T1

You state that you "simply want the two routers to act like bridges". Have you configured them to bridge?

router(config)#bridge 1 protocol ieee

router (config-if)#bridge-group 1

Having said that, I would suggest that you route accross the T1. You will need to re-address some of your network and create another DHCP scope, but I think that it would be worth the effort.

New Member

Re: Point-to-Point T1


It really would be a shame to turn the router into a bridge and flood your whole T-1 with broadcasts.

Try looking at this link to bring you up to speed.

Just change the example 192 network addresses with your 10 addresses to get a feel for what the diagrams are trying to convey.

Yes, you might be new at this network thing, but if you set it up right, you will surely save yourself trouble later on. Write out a plan, cut out a DHCP scope, and subnet your network and you'll be cooking. Most important, look at "NetBIOS over TCP (NBT) " in the first referenced link above.

New Member

Re: Point-to-Point T1


Knowing what you are running on your 'near end' LAN would help - but I would not bridge. Traditional LAN broadcast over T-1 is usually not wise.

If you can (I assume you can) - subnet your private address space and route your datagrams between subnets. Use 'ip helper' on the far end to forward your DHCP requests as unicast or broadcast. Create def. route on far end.

This all assumes you are using private address space and use NAT.