Classic multihoming, ISP path selection using BGP and HSRP(internal)

news2010a · ‎03-15-2009

Hi, can you help me clarify this conceptual questions regarding a perimeter network I am planning to test?

My goal is to make traffic flow thru "ISP1-RouterB" and then use "ISP2-RouterC" in case of problems on ISP1.

Your comments are appreciated. Please attachment for detailed explanation and question in red.

Giuseppe Larosa · ‎03-15-2009

Hello Marlon,

HSRP can be used to provide a next-hop for a default route used by internal devices connected to the lan segment.

You should at least track the state of WAN interface, so that if the wan link fails the HSRP priority on RA is reduced and RB takes over as the new active HSRP.

More fine control can be implemented using object tracking.

see

http://www.cisco.com/en/US/docs/ios/ipapp/configuration/guide/ipapp_hsrp_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1054939

You can use object tracking to track the state of a BGP route to verify if the BGP session is down.

(this is just to avoid ICMP redirect)

An iBGP session between the two routers RA and RB completes the solution where local preference as you plan can provide path selection.

Hope to help

Giuseppe

news2010a · ‎03-15-2009

Great. So then I just do on RA 'neigh RB-IP remote-as #' and the same on RB establishing neighbor relationship with RA.

I will explore the tracking as well.

Thanks!