From: Peter van Oene (pvo@usermail.com)
Date: Wed Feb 05 2003 - 15:51:21 GMT-3
At 10:53 AM 2/5/2003 -0700, Joe Martin wrote:
>Peter,
>
>Thanks for the quick response. I understand the route reflection process (or
>at least I think I do), I just don't see the point of the "no bgp
>client-to-client reflection" command. In your scenario, instead of
>configuring E with no reflect, couldn't you just remove the route reflector
>client command from the neighbor statements for G and H? If I am not
>reflecting routes between clients, I am not a route reflector.
Exactly, but since G and H only peer with E, they are no longer receiving
routes from the rest of the network. For example, all the EBGP learned
routes from the edge that E possesses cannot be advertised to G and H.
>When I configure E with the "route reflector client" command in the neighbor
>statements for G and H, I am making E a reflection server. If I then issue
>the no bgp client-to-client reflection" command, because G and H have
>decided to directly peer, E is no longer acting as a reflection server. It
>is not reflecting routes between clients. What's the point? That's no
>different than just removing the "route reflector client" command from the
>neighbor statements
True, if the network only consisted of E G and H. The question remains,
how do G and H learn about routes from A, B, C and D for example? They
don't peer directly, and having them peer directly would create scalability
problems (n*n-1/2 issues) Adding no-client-reflect simply pulls out the G
and H routes from the set of routes that E reflects. However, E also
reflects all the IBGP learned routes from B C and F and since B and C
advertise routes for A and D respectively, A and D's routes are also in
the mix. So here is a summary.
Consider router G and what it learns from E.
With Reflection on E and G and H non peered, G learns routes from A, B, C,
D, E , F, H from E.
With Reflection on E and G and H do peer * E has no client reflect, G
learns A, B, C, D, E, F from E.
Without reflection and E, G and H peer directly, G learns E from E.
Does that help?
>Hope that explained my point well enough.
>
>TIA,
>
>Joe Martin
>
>-----Original Message-----
>From: Peter van Oene [mailto:pvo@usermail.com]
>Sent: Wednesday, February 05, 2003 10:29 AM
>To: Joe Martin; ccielab@groupstudy.com
>Subject: RE: Route Reflectors and Peer Groups
>
>
>At 10:16 AM 2/5/2003 -0700, Joe Martin wrote:
> >Peter,
> >
> >Could you please explain to me what the purpose of a route reflector is if
>I
> >have configured the no bgp client-to-client reflection command. If the
> >reflection server isn't reflecting routes between clients, what's the
>point?
>
>Most medium to large BGP networks employ a hierarchy of route
>reflection. In these cases, it is normal and indeed necessary to maintain
>multiple route reflection clusters. Therefore, without the route
>reflector, members of a cluster would only learn intra cluster routes. It
>is the route reflectors role to bring extra cluster routes into the cluster
>and to similar export cluster routes to those routes beyond the cluster.
>
>Since that test is pretty confusing sounding and heavy on the cluster,
>consider the below network.
>
>--ebgp-A-------B--------C-------D-ebgp
> | |
> E--------F
> / \ / \
> G H I J
>
>In the above, B,C,E,F represent the IBGP core of this simple network. A and
>D represent two peering routers in network while G to J are regional market
>routers. In this case, you would have BCEF IBGP directly, and have E
>reflect to G and H, and F reflect to I and J. Also, B would likely reflect
>to A and C similarly to D. If G and H chose to peer directly, you would
>enable no client reflect on E, but you will still need E to advertise G and
>H's routes to the rest of the network, and to import routes from the rest
>of the network for G and H.
>
>The above isn't meant to be a best practise network and only an example ;-)
>
>Pete
>
>
> >Is this just used as a migration tool away from or into a route reflector
> >design?
> >
> >TIA,
> >
> >Joe Martin
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> >Peter van Oene
> >Sent: Wednesday, February 05, 2003 8:44 AM
> >To: Brown, Patrick (NSOC-OCF}; ccielab@groupstudy.com
> >Subject: RE: Route Reflectors and Peer Groups
> >
> >
> >At 09:31 AM 2/5/2003 -0600, Brown, Patrick (NSOC-OCF} wrote:
> > >This is what is was talking about from the 12.1 config guide
>documentation
> > >under BGP.
> > >
> > >By default, the clients of a route reflector are not required to be fully
> > >meshed and the routes from a client are reflected to other clients.
> > >However, if the clients are fully meshed, the route reflector does not
> > >need to reflect routes to clients. To disable client-to-client route
> > >reflection, use the no bgp client-to-client reflection command, beginning
> > >in router configuration mode:
> >
> >This is accurate
> >
> > >Note: If client-to-client reflection is enabled, the clients of a route
> > >reflector cannot be members of a peer group.
> >
> >This is odd, but may be an ios limitation. In Juniper, one applies
> >no-client-reflect to the peer group. It is quite normal to have all
> >members of a reflection cluster in the same peer group.
> >
> > >What I interpret from this statment,is that RR can't have clients that
>are
> > >in a peer group they configured(logical).
> >
> >I would tend to agree with your interpretation, though I'm not sure what
> >the technical limitation is.
> >
> > >Tx,
> > >
> > >Patrick B
> > >-----Original Message-----
> > >From: Peter van Oene [mailto:pvo@usermail.com]
> > >Sent: Wednesday, February 05, 2003 7:29 AM
> > >To: ccielab@groupstudy.com
> > >Subject: Re: Route Reflectors and Peer Groups
> > >
> > >
> > >At 10:03 PM 2/4/2003 -0600, Brown, Patrick (NSOC-OCF} wrote:
> > > >Question
> > > >
> > > >Is it true that you can not have neighbors in a peer-group and be
> > > >their route reflector at the same time?
> > > >If this is true, should the "no bgp client-to-client reflection"
>command
> > > >take card of this.
> > > >I have seen labs were this configuration happened.
> > >
> > >Are you asking if clients in a reflection cluster can be neighbors
> > >themselves? peer-groups are just a configuration tool and don't actually
> > >affect the performance of BGP external to the router. If this is that
> > >case, then yes is the answer, and no client-to-client-reflection will
>stop
> > >the reflection server from reflecting intra cluster routes back to
>clients
> > >(since they will be learning these directly)
> > >
> > >Pete
> > >
> > >
> > >
> > >
> > > >Tx,
> > > >
> > > >Patrick B
> > > >.
> > >.
> >.
.
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