BGP failover design

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My company has two primary sites with separate internet connections. Currently we are running eigrp internally with separate default routes and ISP connections to the internet. I would like to propose we run BGP to advertise all public IP address assigned to us as a single AS out both locations. We are both running dual 6513 with FWSM at the core with edge routes connecting us to the internet. I would like to pass all BGP routes to each core to ensure internet failover. I also have a partner company who wants me to redistribute a private /18 network from my EIGRP to BGP. Can one of you cisco wizards give me some high level direction to make this work and keep it reasonably easy to maintain and troubleshoot?

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Amit Singh Fri, 07/06/2007 - 07:43

Hi,

To achieve the BGP redundancy/failover in the dual ISP homing scenario you should have you own block of public IP address range with an AS number. You can use the BGP attributes such as AS_Path and Local_Pref to use one link for outgoing traffic and another ISP link for incoming traffic. Local_prefrence will be use to manipulate the outgoing traffic and AS_Path will factor the traffic which is coming into your AS. You can use ASPATH filterlist to allow the locally originated routes within your AS to be advertised only to the ISP'S i.e you dont want to become a transit AS for both the ISP's.

You cannot have your private network address space to be advertised to the outside world using BGP. This is not allowed. All the ISP's filter the private address space range in their network.

Please see the links below and it should help you undersatnding the designing the network:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c95bb.shtml

http://www.cisco.com/en/US/tech/tk365/tk80/tsd_technology_support_sub-protocol_home.html

HTH,Please rate if it does.

-amit singh

royalblues Fri, 07/06/2007 - 21:05

Friend,

What sup are you running on the Core? The internet had already crossed 220000 routes and it can literally kill your IGP.

You can always redistribute your defualt route from the edge to your core and manipulate the metric so that only one path is alwyas preferred.

Narayan

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