Load Balancing Dual T1s To the Internet

[lui3]

Hey Folks,

Just a quick configuration question for you. My company is planning on adding an additional T1 Frame Relay line in our home office for internet Access. We currently use static routing. My question is this. If we plan on using the two T1 lines to access the internet how do we configure the static default routes to load balance across these two links assuming they have seperate ip addresses from different provider networks. We currently use a cisco 3620 with 4 serial and 4 ethernet interfaces running IOS 11.2 operating system. One serial to the internet and one back to our remote offices. Any configuration examples would be great. Thanks

I was thinking this might work

ip route 192.168.x.x/xx 192.168.x.x Serial 0/0 50
ip route 192.168.x.x/xx 192.168.x.x Serial 0/1 50

What do you think?

Mike

 

[kmcelroy]

If you use the Administrative distance of 50 it is not going to matter because the default is 1 hence the same results. We had a similiar setup like this and it worked perfect for us:

ip route 0.0.0.0 0.0.0.0 Serial 0/0 (One T1 to Internet)
ip route 0.0.0.0 0.0.0.0 Serial 0/1 (2nd T1 to Internet)

We used IP CEF

<snippet from cisco.com>

The two most common mechanisms are per-packet load balancing and per-destination load balancing. Per-packet load balancing distributes the packets across the possible routes in a manner proportional to the route metrics. With equal-cost routes, this is equivalent to a round-robin scheme. One packet or destination (depending on switching mode) is distributed to each possible path. Per-destination load balancing distributes packets across the possible routes based on destination. Each new destination is assigned the next available route. This technique tends to preserve packet order.
</snippet>

Per packet will be more CPU intensive than per destination

 

[lui3]

Thanks for the real world xp. I will move ahead with this config.

Mike