[114733] in North American Network Operators' Group
Re: Multi-homed clients and BGP timers
daemon@ATHENA.MIT.EDU (Olof Kasselstrand)
Mon May 25 04:38:28 2009
In-Reply-To: <4A172B00.9010106@ibctech.ca>
Date: Mon, 25 May 2009 10:38:09 +0200
From: Olof Kasselstrand <olof.kasselstrand@gmail.com>
To: nanog list <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
We have customers in the same way you do. We only use Cisco (both pop
routers and managed cpe) and use
neighbor xxx.xxx.xxx.xxx timers 5 15
on the pop routers with great success. We haven't found any drawback so far=
.
// OK
On Sat, May 23, 2009 at 12:45 AM, Steve Bertrand <steve@ibctech.ca> wrote:
> Hi all,
>
> I've got numerous single-site 100Mb fibre clients who have backup SDSL
> links to my PoP. The two services terminate on separate
> distribution/access routers.
>
> The CPE that peers to my fibre router sets a community, and my end sets
> the pref to 150 based on it. The CPE also sets a higher pref for
> prefixes from the fibre router. The SDSL router to CPE leaves the
> default preference in place. Both of my PE gear sends default-originate
> to the CPE. There is (generally) no traffic that should ever be on the
> SDSL link while the fibre is up.
>
> Both of the PE routers then advertise the learnt client route up into
> the core:
>
> *>i208.70.107.128/28
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0172.16.104.22 =A0 =A0 =A0 =A0 =A0 =
=A0 0 =A0 =A0150 =A0 =A0 =A00 64762 i
> * i =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 172.16.104.23 =A0 =A0 =A0 =A0 =A0 =A0=
0 =A0 =A0100 =A0 =A0 =A00 64762 i
>
> My problem is the noticeable delay for switchover when the fibre happens
> to go down (God forbid).
>
> I would like to know if BGP timer adjustment is the way to adjust this,
> or if there is a better/different way. It's fair to say that the fibre
> doesn't 'flap'. Based on operational experience, if there is a problem
> with the fibre network, it's down for the count.
>
> While I'm at it, I've got another couple of questions:
>
> - whatever technique you might recommend to reduce the convergence
> throughout the network, can the same principles be applied to iBGP as wel=
l?
>
> - if I need to down core2, what is the quickest and easiest way to
> ensure that all gear connected to the cores will *quickly* switch to
> preferring core1?
>
> Steve
>
>
