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New Member

Serial Configuration for Cisco 2801

Hi all,

I have a Cisco 2801 with the following modules:

1 x WIC-1T

1x WIC-2A/S

2x VIC2-2FXS

I would like to configure my Cisco 2801 in the way such that the serial traffic from Router 1 S0/2/0 will route thru S0/3/0 and out from Router 2 S0/2/0. And traffic from Router 1 S0/2/1 will route thru S0/3/0 and out from Router 2 S0/2/1, as shown in the attachment. Please help to advise how can this be done.

Thank you.


Re: Serial Configuration for Cisco 2801

This all depends upon what you know about the traffic and what you want to achieve. If the addressing is simple, static routes may do the trick - eg all traffic to/from blue is in then just have statics pointing 10 where you want blue.

If routing protocols are in use it gets a little more complicated. If you have control, you could do something like put blue on OSPF and red on EIGRP (other routing protocols exists these are just for illustration) you could even look at setting up the link between then to use frame relay and run VRF-Lite to effectively run the traffic as seperate routed networks.

New Member

Re: Serial Configuration for Cisco 2801

But it is v.35 traffic at the both ends of the blue and red line. No ip address in this type of traffic. In this case, how i'm going to use the static route method?

Re: Serial Configuration for Cisco 2801

Ah! Is all the traffic V35? What are you running over the top - PPP? HDLC? X25? FR The protocol will help. It is easier if you are running a crcuit based protocol like X25 or FR as you can configure the routers to be a switch and handle the traffic that way. If you are carrying PPP for example it is a little more involved! Take a look at

New Member

Re: Serial Configuration for Cisco 2801

I don't think my customer uplink is X.25 or FR. It might be a lease line connecting 2 sites. So in this case, i believe that i have to use PPP as the protocol.

Thank you for the link. But i am a little bit confuse because the informations in the link was refering to T1/E1 :(

New Member

Re: Serial Configuration for Cisco 2801

Hi Paul,

I tried to connect a BERT tester to 1 port on WIC-2A/S, and connect the WIC-1T back to back with Router 2's WIC-1T, and configure FR between the routers. And connect another BERT tester at 1 of the port on WIC-1A/S on Router 2.

I did configured the "frame-relay switching" and "frame-relay route" between the interface, but however, the traffic sent by the tester just can get routed to the other side.

Can you pls advise on the configuration? Thank you.

New Member

Re: Serial Configuration for Cisco 2801

I think vrf would be a better alternative just as described in the previous post.

But if you are not familiar with it or not sure about it. There is another non-conventional way to do this stuff.

You can mark the packets as they arrive on Router 1 and on Router 2 based on their marking you divert the traffic. You will have to use PBR for this.