[134130] in North American Network Operators' Group
Re: Router only speaks IGP in BGP network
daemon@ATHENA.MIT.EDU (Mark Smith)
Sat Dec 25 16:30:30 2010
Date: Sun, 26 Dec 2010 08:00:21 +1030
From: Mark Smith <nanog@85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org>
To: ml@kenweb.org
In-Reply-To: <4D15F72A.4060401@kenweb.org>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Sat, 25 Dec 2010 08:52:42 -0500
ML <ml@kenweb.org> wrote:
> On 12/25/2010 3:36 AM, Mark Tinka wrote:
> > On Friday, December 24, 2010 07:26:43 am Randy Bush wrote:
> >
> >> and do NOT redistribute bgp into ospf.
> >
> > This is good truth. Don't redistribute your BGP into the IGP
> > (or vice versa). I'm not even sure OSPF would handle it in
> > this day - but you don't want to find out.
> >
> > Mark.
>
>
> If you're only redistributing 10 prefixes into OSPF? Problem?
>
>
>
I've had to do it when transitioning between a legacy ISP routing
domain and a "BGP for everything" model. The old routing domain had
customer routes in both OSPF and BGP, while the new one used BGP for
customer routes only. As I had to make the new network customer routes
visible in the old network, and the legacy network didn't have a
complete BGP mesh or RR setup (i.e. a broken BGP model), pushing routes
from new BGP into old OSPF was the only choice. I liberally used the
OSPF external route tag and BGP communities to classify routes and to
control redistribution and avoid redistribution loops.
So you can do it, as long as you're very careful, and make sure you
keep reminding yourself that you're playing with a loaded gun with the
safety off. Something definitely worth avoiding if you can.
Regards,
Mark.
