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3640 w/ 3 T1's to same provider Question

I am going to be putting in a 3640 with 3 WIC-1DSU-T1 interfaces. Our provider is going to be installing 3 T1 lines as 1 will not be sufficient. These will be Frame Relay connections all being used strictly for internet access to the provider/ISP. What is the best way to handle routing to these interfaces to ensure proper load distribution across all 3?

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Bronze

Re: 3640 w/ 3 T1's to same provider Question

The router will automatically load share over, up to 4 equal cost paths so you either need to run a routing protocol or have 3 default static routes, one for each T1, eg

ip route 0.0.0.0 0.0.0.0 serial 1/0

This will load share on a per session, rather than a per packet, basis so you may not see equal utilisation. It is possible to force load sharing on a per packet basis by turning off fast switching, 'no ip route cache' on the interface, but this is NOT recommended as it will significantly degrade the throughput of the router.

New Member

Re: 3640 w/ 3 T1's to same provider Question

Does your provider not offer ATM IMA solutions? 4.5 meg IMA circuits are more common than 3 t1 frame connections and more cost effective. (it's still 3t's just with atm encap to a virtual ima connection instead of frame. ) Static routes of equal cost and destinations will load share.

Bob Watson

SBC Datacomm Implementation Engineer

CCNP, CCDA

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