[nsp] Tri-homed with HSRP

[Pete Templin]

Something to consider: HSRP works great, so use it again.  Set up a second standby address, and make RTR2 the most preferable.  Point 1/3 to 1/2 of your hosts to it, and 1/3 to 1/2 of your outbound traffic should shift to the other router.

Pete Templin
Senior Staff Engineer
TexLink Communications
(210) 892-4183
pete.templin at texlink.com


-----Original Message-----
From: tgrace [mailto:tgrace at tgrace.com]
Sent: Thursday, September 04, 2003 4:17 PM
To: 'David Sinn'; cisco-nsp at puck.nether.net
Subject: RE: [nsp] Tri-homed with HSRP

I've tried reversing roles and I just move the problem. Metrics are equal
because 2 or more of my ISPs have peering links to the destination networks.
I'm not concerned about inbound traffic, just outbound.

-----Original Message-----
From: David Sinn [mailto:dsinn at microsoft.com]
Sent: Thursday, September 04, 2003 1:36 PM
To: tgrace; cisco-nsp at puck.nether.net
Subject: RE: [nsp] Tri-homed with HSRP


There are multiple ways to play with BGP (and IGP) to change the behavior.
You could switch HSRP to RTR2, but that may put you back in the same boat
for some other set of prefixes that are better via ISP1 but are equal via
your BGP metrics.  You could throw routers at it and get IGP involved to
break the tie (or traffic engineer what you want to happen).

I guess a more fundamental question is, why are the BGP metrics equal? Is
this something that could be solved by modifying the metrics because the
prefix's you are trying to get to are customers of ISP2 or 3 and not ISP1?
(I.E. Are you leveraging communities from your ISP's to help you make a good
decision?  Do you have any "good guesses" in your BGP policy where
communities aren't available?)

David

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of tgrace
Sent: Thursday, September 04, 2003 5:23 AM
To: cisco-nsp at puck.nether.net
Subject: [nsp] Tri-homed with HSRP

We are tri-homed using two 7206VXR's. RTR1 is our HSRP master and hosts a
link to ISP1. RTR2 is our HSRP backup and hosts links to ISP2 and ISP3. We
are getting some performance issues because traffic entering via ISP2 or
ISP3 is returning via ISP1 due to BGP metrics being equal and RTR1 being the
default gateway. Is there anyone way to force traffic out its origin link
when BGP metrics are equal?

TIA for any advice.


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