BGP Selective Download

[Federico Coto Fajardo]

Hi Community,

Appreciate if someone could clarify for me the following question...

I have RRs that I don't want received BGP routes to be installed in the RIB (both IOS/XR).

So, I see the use of the BGP Selective Download which uses a Route Map accomplish this (IOS). 

Is this the correct way to do it?

The other clarification is with the (IOS) "bgp default route-target filter" or (XR) "no retain route-target all".

The above is to allow/disallow routes into the BGP table itself regarding the RTs (nothing to do with the RIB) correct?

Thanks!

Federico.

[Federico Coto Fajardo]

If I posted on the wrong community, please advice.

Anyone?

Thank you,

Federico.

[Andre Gustavo Albuquerque · Accepted solution]

BGP selective download is the way to accomplish what you want.

Regarding the route-filter statements, the default behavior on IOS and IOS-XR is to discard VPN prefixes if there is no local VRF importing them.

When a neighbor is configured as route reflector client, this behavior is changed, and RTs are retained.

And, if you have a situation where the router is not reflecting routes, and needs to propagate this to other router (example: PE-ASBR in an Inter-AS option B scenario, or RR in a Inter-AS option C scenario), you need to change the default behavior using the commands you mentioned.

Cheers, Gustavo

[Federico Coto Fajardo]

Thank you Andre, but specifically when you mention:

Regarding the route-filter statements, the default behavior on IOS and IOS-XR is to discard VPN prefixes if there is no local VRF importing them.

My question is, the router prevents the route from being installed in the BGP table or in the RIB?

My understanding is that if there are no VRF importing them, the routes don't make it to the BGP table (therefore not to the RIB), is this correct?

Federico.

[Andre Gustavo Albuquerque]

My understanding is the same as yours.

The filtering behavior is implicit and is the same as using other means (eg.: route-map).

Cheers, Gustavo

[Federico Coto Fajardo]

Let's say I have RR 1.

This router is accepting all routes since it's a RR and does not perform the RT filtering by default.

These routes will make it to the BGP table but not to the RIB (since there are no VRFs configured to import those routes) is this correct?

The part I don't understand is why RR1 is installing the routes in the RIB. I thought it will accept all routes in the BGP table (regardless if the import RTs are there because is a RR), but only in the BGP table. Should not download those to the global IP routing table, or it should?

Thanks again,

Federico.

[Federico Coto Fajardo]

Andre,

It was my confussion.

I am seeing IPv4 routes getting installed in the RIB, the VPNv4 routes are not (in the RR), so it's expected behavior.

Thanks for all your help.

Federico.

[Andre Gustavo Albuquerque]

Great!
Cheers

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