[c-nsp] Mutual redistribution into and out of the MP-BGP superbackbone

[Phil Bedard]

IOS-XR has the ability to apply a policy to the redistribution command for
both OSPF and BGP so you can filter out the routes you do not want
redistributed.   

Is there a reason you can't just configure BGP to advertise aggregates
covering the OSPF routes as opposed to doing mutual redistribution?

Phil 

On 2/9/12 7:43 PM, "Jason Lixfeld" <jason at lixfeld.ca> wrote:

>If I redistribute OSPF routes into the MP-BGP/superbackbone from within a
>particular VRF, those OSPF routes, which are now BGP routes, get
>announced to any BGP speakers inside the same VRF.
>
>Conversely, if I redistribute BGP routes from the MP-BGP/superbackbone
>into OSPF within a particular VRF, those BGP routes, which are now OSPF
>routes get advertised to all OSPF routes inside the same VRF.
>
>Normally this would't be an issue, except in this particular case, the
>VRF where the mutual redistribution is happening happens to hold a full
>BGP table.
>
>Two issues here.  1)  It's a bit silly to have an OSPF router see every
>prefix in the Internet routing table as an OSPF route.  2)  It's a bit
>silly for BGP sessions inside the same VRF to see every single OSPF
>prefix as a BGP route.
>
>I can wrap the redistribute ospf x with a route-map and set local-AS,
>which will prevent eBGP speakers from receiving those OSPF routes.  iBGP
>speakers, however, will still receive those OSPF routes as BGP routes.
>Setting no-advertise will likely break the superbackbone, so I don't
>imagine I can use that as a solution.
>
>In the BGP into OSPF case, I'm drawing a blank on how to prevent the BGP
>routes from clogging up the RIB on other OSPF routers.  Again, any
>particular BCP or nerd knob?
>
>I'm labbing this in IOS, but the redistribution, when moved to
>production, will happen on XR devices.
>
>Thanks in advance for any ideas.
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