[j-nsp] BGP route-reflection question

Guy Davies Guy.Davies at telindus.co.uk
Wed May 28 10:15:06 EDT 2003

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If there is a connection between RR1 and RR2 then the client will maintain
iBGP connections to both of the RRs.  Remember, iBGP is inherently capable
of multihop.

The other possible solution for getting RR1 to accept routes from RR2 is to
give them both different cluster IDs.  There is no requirement for all RRs
associated with a single "cluster" to have a common cluster ID.  Therefore,
each RR would see the other's cluster ID in the cluster list and accept the
prefix.  However, it would still be receiving a better path direct from the
client (shorter cluster list) :-)

To answer your question.  Intracluster reflection is client-to-client
reflection (i.e. routes learned by RR from client A will be reflected to
client B) so there is no requirement for a full mesh within the cluster.  If
you want to turn this off then you can do so with "no-client-reflect" in the
particular group.



> -----Original Message-----
> From: Dmitri Kalintsev [mailto:dek at hades.uz]
> Sent: Wednesday, May 28, 2003 8:00 AM
> To: juniper-nsp at puck.nether.net
> Subject: [j-nsp] BGP route-reflection question
> Hi All,
> Let's imagine that I have two straight ipv4 BGP route 
> reflectors in the same
> cluster, say R1 and RR2. Now imagine that I have a reflector 
> client, which
> is:
> a) Connected to both of them via dedicated point to point links;
> b) Advertising the same routes to both of them.
> Now imagine that one of the point to point links (say client 
> to RR1) has
> failed. Client would still advertise it's routes to the RR2, 
> and RR2 would
> readvertise them to RR1.
> The experience that I had with other vendor's equipment is 
> that RR1 would
> not accept the client route advertisements from RR2, because 
> it would reject
> them having seen it's own cluster ID in these. The only way 
> to make this
> work was to remove the cluster ID (cluster list is used 
> instead to prevent
> routing loops).
> In JunOS, it is a prerequisite and the only way to configure 
> route reflector
> client by setting the cluster ID in the bgp group to which the client
> belongs.
> http://www.juniper.net/techpubs/software/junos/junos57/swconfi


"By default, the BGP route reflector performs intracluster reflection
because it assumes that all the client peers are not fully meshed."

Could anybody please clarify to me how this is implemented in JunOS and this
"intracluster reflection" is?

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