Router only speaks IGP in BGP network

Dear all

In my network, I have a router in a middle only speaks OSPF.
is there any solution (without redistribute BGP into OSPF) for this kind of problem?

thanks

Hi Andre

That actually what I had done..
I thought it might be another solution

many thanks

In a message written on Thu, Dec 23, 2010 at 09:18:57PM +0300, Tarig Yassin wrote:

In my network, I have a router in a middle only speaks OSPF.
is there any solution (without redistribute BGP into OSPF) for this kind of problem?

Sounds like the textbook case of how folks use MPLS.

Hello Tarig,

Setup a gre tunnel between the two bgp speakers and do ibgp over the
gre tunnel? (not clean but it works) or mpls..
If you implement the other solution mentioned you're creating routing loops.

You could use a GRE tunnel to get traffic from one edge BGP outer to the
other edge BGP router. Then run BGP over this link.

- Brian J.

From: Tarig Yassin [mailto:tariq198487@hotmail.com]
Sent: Thursday, December 23, 2010 12:19 PM
To: nanog; afnog@afnog.org
Subject: Router only speaks IGP in BGP network

Dear all

In my network, I have a router in a middle only speaks OSPF.
is there any solution (without redistribute BGP into OSPF) for this

kind of

problem?

thanks

--
Tarig Y. Adam
CTO - SUIN
www.suin.edu.sd

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In my network, I have a router in a middle only speaks OSPF.
is there any solution (without redistribute BGP into OSPF) for this
kind of problem?

uh, what exactly is the problem? i.e. what do you want to accomplish?

and do NOT redistribute bgp into ospf.

randy

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?

Oh please. OSPF loves it when you shove a few 100k routes into it.

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.

I know I'm a little late to this thread, but figured I'd point out one
reason why this can be very dangerous:

In IOS, you use a route-map to control redistribution between protocols.
For example, if you want to redist just those BGP prefixes tagged with a
specific community into OSPF, you will probably configure something that
looks like this:

    route-map bgp-to-ospf permit 10
     match community $COMMUNITY
    !
    route-map bgp-to-ospf deny 20
    !
    router ospf $PID
     redistribute bgp $ASN subnets route-map bgp-to-ospf

Now, consider the following failure scenarios:

1. Someone typo's a BGP config elsewhere in your network and attaches
$COMMUNITY to a whole bunch more routes... say, all 350k being sent by your
upstream provider. *oops*

2. An engineer thinks that there's something wrong with the redistribution
and decides to temporarily disable it as part of the troubleshooting
process. He types the following:

    conf t
    router ospf $PID
    no redistribute bgp $ASN subnets route-map bgp-to-ospf

*boom*

He just dumped all BGP routes into OSPF, due to the way IOS parses the
command: it removes the route-map but leaves the redistribution intact.
To be fair, Cisco does provide you with tools to mitigate this risk (see
the "redistribute maximum-prefix" command) but the point is that this is
a fairly easy mistake to make.

At the end of the day, the reason that many folks advise against the
redistribution of BGP into an IGP is that it sets the stage for a seemingly
insignificant mistake to cause a not-so-insignificant outage.

--Jeff

This is an interesting point.
But why cisco *no* command does not remove the redistribute , I think it should do.

Thanks