CCNP - 2 ISPs backbone..!!

Author

2 ISPs backbone..!!

Joe_1

2003-05-20, 12:36 am

Dear All,

I would like to Know how it’s gonna be if I wanted my internet connection to be via 2 different ISPs, I just want to know about what must be done on my router side and the 2 ISPs routers, and how I’m gonna use both links at the same time, and what about the routing and security..

Regards..
John

anchor40

2003-05-20, 7:41 am

It depends...

Do you want to load share or use one as a back-up?

If loadshare, then BGP is the way to go. If the 2nd ISP is only to back-up the first, then you can get away with a static route to the first ISP and a floating static to the 2nd ISP.

BGP is policy-based routing, and can get quite complex, but there are several example config's on CCO on how to accomplish the loadsharing.

Mad21maxx

2003-06-24, 2:45 pm

Anchor is it possible to instead of running BGP for loadsharing to both ISPs, to setup two static routes each pointing to their respective ISP but both having the same administrative distance?

Thanks!

anchor40

2003-06-24, 4:09 pm

I wouldn't think so - what would your static routes look like?

Since you're talking Internet traffic, if you're not running a routing protocol with your ISP, you need a default static route to the ISP, and the ISP needs a static to your network for the return packets. There is no mechanism to determine if that ISP is up or down - only that all packets should be sent there.

I'm not sure you can configure default static routes to each ISP with the same administrative distance, because the router would get confused as to which path to send packets. If it is possible, then some packets would be sent to ISP 1, and others to ISP 2, with no mechanism to compensate for one of the links being down (result - lost and/or out-of-sequence packets).

It all comes down to what problem you're trying to solve. If your Internet connection absolutely HAS to be up, AND the business requires you to utilize any circuits (rather than them site idle until a problem occurs), then there is your justification for two routers and running BGP and a routing protocol between your premise routers (to handle any failure).

Otherwise, go for circuit redundancy with two static default routes with different adminstrative distances.

HTH...

Mad21maxx

2003-06-24, 5:50 pm

Thanks for the response. It all seems very clear now.

netkamoze

2003-06-25, 7:00 am

I once solved a problem like that by using route-maps. Quite useful for defining which users go thru which ISP..also can be used as a backup link config.it worked quite well.

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