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New Member

Load Balance over 3 T1's


I am new to the cisco world and have a sitatuin I would like to better. We currently have 3 T1's 2 from one provider and one from a different provide. Each one finds its way into a cisco 2600 router. I would like to find out how to load balance across all three along with offer failover capabilities. Can someone point me to a good article or give me a good direction to go from here. Thanks for the help in advance.


Re: Load Balance over 3 T1's


Is it a point-to-point T1's (Private Links) or going through to internet ? If it is a PPP circuit, you can just enable CEF and do per-packet load balancing. You can just enable routing for the destination subnet across all three links and make sure the packets gets load balanced.

ip route serial 0/0

ip route serial 0/1

ip route serial 1/1

In this case, all the three entries go into the routing table and incase any link goes down, the other two will take the traffic..

Incase the T1's are not point to point, you need to do multihoming (since there are 2 ISP's) with a protocol called BGP, which is a little complex and tough to explain here. You can search in CCO and read about BGP if this is ur scenario.

Hope this helps. rate replies if found useful..



Re: Load Balance over 3 T1's

In addition to Raj's post. You can also consider Multilink PPP, it will load sharing the links at PPP layer instead of at routing level.

Check below for more info.

Moreover, if you use MLPPP, you have to check the CPU loading during the test and do beware of the cable connection sequence at both ends. Both ends should have the same sequence to connect to remote side.

If depends on the situation and you better carry a test for two solutions to determine a suitable one for you.

Hope this helps.

New Member

Re: Load Balance over 3 T1's

The part I am a little unclear on is that each T1 currently runs into its own 2600 router. Can I configure all this with all three routers or should I change the hardware configuration. Thanks.

Cisco Employee

Re: Load Balance over 3 T1's


The situation is slightly complicated here as you have 3 links, 2 from one provider and 1 from the other provider.

Are these connections used for internet?

If yes,My Idea for this would be to run HSRP/GLBP between the routers from the same service provider and then use PBR to have some of the traffic to use one service provider or some traffic to use the other service provider. For example let HTTP traffic to use the ISP1 and FTP/Mail traffic use the ISP2. These both the ISP's will be configured as a backup of each other and incase of one of the ISP completely down on you the ISP will take care of forwarding all the traffic.

Please see the link below for PBR configuration:

HTH,Please rate if it does.

-amit singh


Re: Load Balance over 3 T1's

I am sorry that I overlooked two links from one ISP and one from another ISP. I agreed w/ Amit's suggestion but you have to consider the CPU loading when use PBR. It is a CPU intensive feature.

If you enable the PBR, you have to check the CPU loading in order to consider to upgrade the router model.

Due to three links are provided by two ISPs, it is better to manual load-sharing it better utilize the bandwidth.

Hope this helps.