Routing Policy with Multihomed, Multi-ISP BGP Network

[thiland]

Configuration:

R1-->ISP1

R2-->ISP2

R1<--iBGP/HSRP-->R2

R1=HSRP Active router

IOS 12.2

I have a case where I am advertising one /24 network via BGP to both ISP1 and ISP2. In an effort to resolve some asymmetric routing issues, I'd like to do the following:

I would like to specify that 1 IP address in my /24 space always use ISP2's link, unless it goes down, then use ISP1. My original thought was to create a route-map specifying the source IP address, and setting a localpref to 150.

However, the problem is since both routers are sourcing the /24 network, by default they have a weight of 32768. Since weight is a higher priority than localpref, my routing policy never gets used.

Any ideas on how to prefer an ISP for a single IP address, while maintaining redundancy?

[mpabilona]

You can create an additional single virtual ip in your hsrp where R2 is the active and R1 is standy router. Any network using that gateway virtual IP will prefer the path via R2.

[prafuljaded]

Hi Tanner,

I too am implementing the BGP multihoming scenario almost similar to yours.I guess you are using the /24 IP space from only one of your ISPs.I have a PIX firewall Outside connecting to my two 7206s (R1 and R2) with HSRP and iBGP running between the two 7206s.Is HSRP running fine with your outgoing BGP policies set, bcoz using HSRP you can have a single active forwarding router at any point of time. Lets say you have R1 as HSRP active router and want to push some traffic via R2, redirect happens from R1 to R2 in the LAN, right ?

Praful