[119225] in North American Network Operators' Group
Re: about interdomain multipath routing.
daemon@ATHENA.MIT.EDU (Matthew Petach)
Tue Nov 10 04:23:58 2009
In-Reply-To: <970c8dea0911100110n5c547297u260964431a045220@mail.gmail.com>
Date: Tue, 10 Nov 2009 01:23:13 -0800
From: Matthew Petach <mpetach@netflight.com>
To: Doug Lane <laned1@gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Tue, Nov 10, 2009 at 1:10 AM, Doug Lane <laned1@gmail.com> wrote:
> On Tue, Nov 10, 2009 at 3:50 AM, Matthew Petach <mpetach@netflight.com> w=
rote:
>> I've outlawed the use of multihop eBGP for load-sharing here; when we ge=
t
>> multiple links off the same router to a peer or upstream, they are confi=
gured
>> with multipath. =A0We've got hundreds of BGP sessions across the network
>> configured with multipath on them.
>>
>
> Do you use iBGP multipath as well to load-balance between links on
> different routers?
Yes.
> I know eBGP multipath is fairly common, but I wonder how many are
> using iBGP multipath as well. I doubt any carriers would support it,
> so it's probably only useful for load-balancing outbound traffic. The
> problem with eBGP multipath alone is that you might want to terminate
> circuits from a given carrier on two different routers for redundancy
> reasons, but that precludes any load-balancing with eBGP multipath.
> Obviously your network has to be designed with equal-cost paths for
> iBGP multipath to be of any value.
>
> -Doug
iBGP with multipath, multiple LSPs to each BGP next-hop...much load
balancing across all same-cost internal links to each of the eBGP
multihop next-hops.
inet.0: 300787 destinations, 2675963 routes (300092 active, 2
holddown, 2086 hidden)
Yes...takes up a chunk more memory keeping track of all the
different paths, but it does provide more end-to-end load balancing
of traffic even on different routers.
Matt
