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Dynamic routing

Unanswered Question
Oct 29th, 2003
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Hi there,

I have a situation.... I need to keep all my wan links running optimally!

I am thinking of implementing 2 ISP's (different) so that I have a backup line running to my router. From my router I connect to a pix.. then to the LAN and so on.

My question is what is the best way to do this if I want to dynamically allow traffic to flow in and out of the pix when a link dies on the router?

So effectively, if the main line dies, how can a make the router automatically route traffic to and from the pix through the 2nd wan link.

The reason is our authenication servers will be based a one site...we have multiple sites and if a link at any site dies it means users can't authenticate! This is design from up above that we have to live with and work around... crappy if you ask me but we have to come up with a solution to allow for minimal downtime.

The secondary line is our idea but we aren't sure how to dyamically change routes when one dies...

Thanks in advance and I look forward to hearing from you.


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Harold Ritter Wed, 10/29/2003 - 08:22
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If you are connecting to two Servive Provider with the same prefix then the only option is to run BGP with them. I personally wouldn't have a primary and a secondary and would use both links but if for some reason you absolutely need to have a primary/secondary scenario then you can set the local preference on updates received from the secondary SP and use conditional advertisement to advertise your own prefrix to the secondary SP on if you stop receiving routes from the primary SP.

Hope this help,

ruwhite Thu, 10/30/2003 - 08:34
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You could use static defaults, pointing to the serial interfaces, and redistributed into the IGP you're using. You could load share equally with this method, or adjust the metrics/admin distances so that only one is used at a time.

You could also run BGP with both service providers, and just announce your route to both, using a private AS number. They would strip the private number out.


spremkumar Sat, 11/01/2003 - 20:18
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can neone post a sample config considering the abov said conditions ??




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