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When is the Cluster list created or updated and when not 

can any body give em a clear idea 

When is the Cluster list created or updated and when not 

can any body give em a clear idea 

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will RR create a CLUSTER_LIST even if it adverties prefix to an external peer 

or it removes the CLUSTER_LIST 

CLUSTER_LIST

   Cluster-list is a new optional, non-transitive BGP attribute of Type
   code 10. It is a sequence of CLUSTER_ID values representing the
   reflection path that the route has passed. It is encoded as follows:

             0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Attr. Flags  |Attr. Type Code|   Length      | value ...
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where Length is the number of octets.

   When a RR reflects a route, it must prepend the local CLUSTER_ID to
   the CLUSTER_LIST.  If the CLUSTER_LIST is empty, it must create a new
   one. Using this attribute an RR can identify if the routing
   information is looped back to the same cluster due to mis-
   configuration. If the local CLUSTER_ID is found in the cluster-list,
   the advertisement received should be ignored.

So this are the fundas right 

The CLUSTER_LIST is created or updated on RR only during Reflector :

1.      when a route is reflected

                   from 1 client to another client / non-client

                   from a non-client to a client

    When a CLUSTER_LIST is not created:

                  1.      If an RR originates a route, Originating RR does not create a CLUSTER_LIST.

                  2.      When RR advertise a route learned from external peer to its client and non-                             client, RR does not create a cluster list

    When RR advertise prefix to external peer, the existing CLUSTER_LIST is REMOVED 

for more info u can refer to

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c95bb.shtml

Thanks

Now i got clear in mind thank you for all reply