[c-nsp] BGP load-sharing *and* redundancy across 2 routers

[Robert Gutierrez]

My ISP is willing to do 2 different loopback eBGP sessions, so my problem
is solved.

But in failure analysis testing, I hit CSCsq43831.  Ground my RSP almost
to a halt before I downed the interfaces to remove the static routes.
Looks like I'll have to go to 12.2(33)SRB4.

    rob


-----Original Message-----
From: Adam Armstrong [mailto:lists at memetic.org] 
Sent: Tuesday, October 21, 2008 1:47 AM
To: Robert Gutierrez
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] BGP load-sharing *and* redundancy across 2 routers

Robert Gutierrez wrote:
> Hi all.  I have a typical BGP loopback setup to my ISP.  4 links across
2
> routers.  2 links on each router. Easy -- no problemo.
>
> Now, how can I get loopback address redundancy?  I'm currently using
> Router "A" as my loopback address, with an iBGP to Router "B", and
> multihop and maximum-paths set up.  So Router "A" knows about all 4
links
> outbound.
>
> Now, if I lose Router "A" (crash, power-off, etc), I want Router "B" to
> pick up the peering of it's 2 links, and bring the BGP session back up.
> The only way that I can figure out is (1) Make the loopback address an
> HSRP across both routers (is that even possible or been done?), or (2)
> Just bring up sessions on both routers using the same Loopback address.
>   
You don't really want to do this. It'd only cause your links to flap a 
second time when the router came back up.

What are the links? Ethernet? Serial? If you're taking ethernet from the 
provider, why not just use switches so that both routers can talk across 
all of the links? It would mean 8 sessions though.
> I guess the "right" way is to use 2 different loopback addresses, one
for
> each router, and bring up peers for both, and use MEDs or their
community
> map to make them pref one way or another across each loopback peer (with
> myself using local-pref).  Do you know of any Tier-1's that let you do
> this?
adam.