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Mulithomed Question

Hi,

Can anyone suggest something useful for the following problem.

Our company is multihomed to 2 ISPs.

One of them is a FR connection with a public subnet assigned to us by the ISP.

The other one is an ADSL line with one fixed IP address. (we are NAT-ing every request going to that direction.)

Currently we are doing a basic per-session load-balancing. It works really nice.

If one of the lines/isps fail we still have service without intervention.

The following request from my managers gives me a headache:

We need to route certain url requests to the FR. I can do it with NBAR and policy routing. The problem is that I loose redundancy for these urls since they are forwarded to the FR even if it's down. In this case I have to reconfigure the router's policy for the FR downtime.

Can anyone suggest a good solution? (Participating the internet BGP routing is not an option.)

thanks,

Attila

1 ACCEPTED SOLUTION

Accepted Solutions
Gold

Re: Mulithomed Question

Is i failing because the frame interface fails to go down, or because even though the frame interface goes down, the policy routing is still forwarding traffic along that route? In order to make certain the frame interface is going down, you can use end-to-end lmi , or a bit signalling, to make certain that the router knows the dlci has gone down. You might need to put the frame circuit on a point-to-point subinterface to get this to work, but I'm not exactly a frame expert.

On the second part, if the frame interface is failing, then you should be able to place an alternate next hop in the route map you're using for policy routing, so that if the first link fails, the second one is used. Just list the alternate next hop after the primary one:

ip set next-hop x.x.x.x y.y.y.y

should work, though I've not tested it in the lab to be certain.

Russ

3 REPLIES
Silver

Re: Mulithomed Question

I think you can try giving multiple hops in "set ip next-hop" command for route-maps. In case first hop is not reachable/down, the second one is used.

Hope this helps.

thanks

New Member

Re: Mulithomed Question

Thanks,

I'll test it.

Attila

Gold

Re: Mulithomed Question

Is i failing because the frame interface fails to go down, or because even though the frame interface goes down, the policy routing is still forwarding traffic along that route? In order to make certain the frame interface is going down, you can use end-to-end lmi , or a bit signalling, to make certain that the router knows the dlci has gone down. You might need to put the frame circuit on a point-to-point subinterface to get this to work, but I'm not exactly a frame expert.

On the second part, if the frame interface is failing, then you should be able to place an alternate next hop in the route map you're using for policy routing, so that if the first link fails, the second one is used. Just list the alternate next hop after the primary one:

ip set next-hop x.x.x.x y.y.y.y

should work, though I've not tested it in the lab to be certain.

Russ

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