Configuring a T1 and DSL on the same router

[robzamani]

Hi ,

I have a 2811 router . My client needs to connect his existing T1 connection and also needs to bring in his DSL connection to the same router.

How can I configure this router so that both WAN coonections are active and I can do some load balancing .

Thanks ,

Karthik

[Richard Burts]

Karthik

If both interfaces are properly configured and connected then they should both be active.

The easy way to get load balancing is to configure two static default routes, one default route will point out the T1 and the other default route will point out the DSL. This is easy and effective. There are some downsides to this including the possibility that there might be assymetric paths in which a packet arrives on one interface and the response is sent out the other interface. There is also the possibility that you could lose connectivity over one of the interfaces but the default route could still be in the routing table and you could be sending packets out an interface that is not working and they would never be delivered.

Whether these issues are serious enough for you to not want to use them is something that you and your client will need to decide.

There are some alternatives that you might consider. There is a new feature called Enhanced Object Tracking that you might find useful. It tracks the reachability of remote entities (including remote IP addresses). This feature can be used with static routes to ensure that if the interface stops working that the static route is withdrawn from the routing table.

HTH

Rick

[robzamani]

Thank you for your response. Asymmetric routing may indeed become a problem. The way this is going to be setup is like so :

WAN ROUTER -- T1 and DSL

PIX Firewall -- IP outside from the range provided by T1 provider. VPN tunnels terminating on outside interface

LAN SWITCH.

I know that this is not the right way to do it , but the customer has the DSL and T1 and he wants to use both as he will lose money if cancels out of either one.

VPN is going to be very important as that would carry the site to site Active Directory traffic .

My initial question was how would I configure a router with a T1 and DSL and what modules would I need . Do I need a module for DSL or do I just run an ethernet cable from the DSL router back into my router ?

[Richard Burts]

Karthik

If the WAN router with the T1 and the DSL is outside of the PIX firewall, then the PIX will not see any assymetric path. It does not know how data came to the router or how the router will forward packets. It only would know that the packets came from the router to the PIX on the same interface and went from PIX to router on the same interface. So it looks like no issue with assymetry.

What modules you need and how to configure the router will depend on how the DSL is provisioned. If there is a DSL router then it probably will just be a standard Ethernet connection between the DSL router and an Ethernet/FastEthernet interface on your router. So you will need to be sure that the router has at least 1 serial interface for the T1, and at least two Ethernet/FastEthernet interfaces (one Ethernet for the DSL and one Ethernet for the interface to PIX).

HTH

Rick