Will HSRP watch a BGP session?

Posted on 2009-02-12
Last Modified: 2012-06-21
Hello all, I know there is alot out there about Cisco HSRP but have not seen the answer to my question.  I am in the process of modifying my current environment from all 3 ISP's using eBGP to annouce my 1 class C IP space all from a single border router, which is a single point of failure.  So my goal is to connect each ISP to its own router.  This is good for us because not all the ISP's come from the same medium and even enter my network in the same building, so I will gain geographic separation and redundancy as well.  I want the topology to look like this:

ISP A       ISP B         ISP C
 |                |                |
 |                |                |
BldgA       BldgB         BldgC
RtrA          RtrB           RtrC  - All running eBGP to ISPs annoucing 1 class C
 |                |                |
--------L2 Switching----------
     Redundant  PIX

Ok my HSRP question is:  I see alot that HSRP looks at interfaces to determine if the active router is alive.  I understand this benefit when hardware fails.  But in my BGP environment its much more likely that the BGP session with the ISP will go down with the router's physical or logical interface remaining up/up.  So, will HSRP respond if just the BGP session with that ISP goes down and not the connected interface?

Many thanks.
Question by:kbws1
    LVL 43

    Accepted Solution

    No, it doesn't.  You can either run iBGP between all 3 routers so if the link to ISPA goes down but RtrA is the HSRP active router, RtrA will forward traffic to RtrB or RtrC and out to the Internet.  Or, you can run OSPF on the 3 routers (along with BGP) and advertise the BGP default via OSPF to the PIX.  In this case, if ISPA is down, RtrA stops advertising the default learned via ISPA and only ISPB and ISPC are used.  I would go with the second method instead of the first.
    LVL 79

    Assisted Solution

    I'd go along with JFrederick29 on this one. Using dynamic OSPF routing between all three routers and the PIX's is the cleanest and easiest solution with fastest convergence time. HSRP is simply the wrong solution for this application.
    Just advertise a default from each of the 3 routers. You might even see some load-sharing going on.
    Else use IP SLA monitoring on the routers to determine if the route is gone but the link is still up.

    Author Closing Comment

    Thanks for the suggestions.  I will go with OSPF.

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