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Load Balancing 2 T1s


Hi all,

I have a 2611 with 3 ethernet interfaces. 2 are used to connect my internal LAN and the third is used to connect to my ISP. This router is currently NATing all my individual networks. Now my question is how do I make this router or the third interface load balance between 2 T1's that are on a Hub or switch with the 3rd interface connected to the same hub or switch. Any help would be great.

2 Replies 2

Erick Bergquist
Frequent Contributor
Frequent Contributor

What type of equipment do the T1s come in on, other routers plugged into a hub/switch on your 3rd ethernet segment? Does the switch have FlexWan (?) ports capable of handling T1s? Is this a metro type of connection (Ethernet from carrier)?

since you are NAT'ing and I'm presuming the 3rd interface is the NAT outside address if these 2 T1s are to 2 different ISPs then NAT'ing may be a problem depending on how your address assignments are. Need more details.

As far as load balancing, it is 1 ethernet connection from your 2611 to this hub/switch where these T1s are coming into if I understand correctly. You could put 2 default routes on the 2611 pointing to the IP address next-hop for each T1 and then you'll have 2 equal-cost routes. But this may not work depending on how these T1s are coming in.

Can you provide some more details on the connection?

The connection is metro. The T1's are plug directly into a switch as well as my NAT router's outside interface. The outside interface is setup with an Ip address assigned by my ISP from one of the T1s. Now if I put default routers in my configs, would I have to assign a secondary address or would I just be able to just put in configs for half my networks NATing to the other block of IP address on the 2nd T1. Does this help in picturing what the connections look like. Again thanks for the help.

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