ROUTE REFLECTOR UPDATE

ROUTE REFLECTOR UPDATE

Number of NLRIs in the update sent: max 1, min 1 Update messages formatted 5, replicated 0 Has 2 members (* indicates the members currently being sent updates):īGP version 4 update-group 2, internal, Address Family: IPv4 Unicast Minimum time between advertisement runs is 0 seconds Number of NLRIs in the update sent: max 1, min 0 Update messages formatted 59, replicated 47 The route propagation policy of a route reflector is also displayed in the show ip bgp update-group printout: RR#show ip bgp update-groupīGP version 4 update-group 1, internal, Address Family: IPv4 UnicastĬommunity attribute sent to this neighborĮxtended-community attribute sent to this neighbor Origin IGP, metric 0, localpref 100, valid, internal, multipath, best The same command executed on a route reflector will also indicate whether a route was received from a route-reflector client (and will thus be reflected to all IBGP peers): RR#show ip bgp 10.2.2.0īGP routing table entry for 10.2.2.0/24, version 18 Origin IGP, metric 0, localpref 100, valid, internal, best The route reflector-related BGP attributes attached to a BGP route ( Originator and Cluster list) can be inspected with the show ip bgp prefix command: Edge#show ip bgp 10.2.2.0īGP routing table entry for 10.2.2.0/24, version 12 The link bandwidth community is removed from reflected route if the route-reflector performs IBGP multipath load-sharing for that route.Standard and extended BGP communities are removed from the reflected routes unless the neighbor send-community is configured on the route reflector.BGP next-hop can be changed set ip next-hop route map command or with neighbor next-hop-self all feature introduced to support large-scale DMVPN networks using IBGP.The next-hop-self neighbor configuration parameter or (most of the) set options of outbound route-map configured on route-reflector clients are ignored for reflected routes. Route reflector does not change or remove any other attributes of the reflected routes (even non-transitive attributes), ensuring that the IBGP routes are not changed within the autonomous system. The value configured with the bgp cluster-id router configuration command (or the router ID of the route reflector if the cluster-id is not configured) is prepended to the Cluster list attribute.If the route does not have the Cluster list attribute, it’s added to the route.

If the route does not have the Originator ID attribute (it has not been reflected before), the router ID of the IBGP peer from which the route has been received is copied into the Originator ID attribute.

Whenever an IBGP route is reflected (propagated to another IBGP peer), the route reflector appends two optional, non-transitive attributes to the BGP route:

Routes received from a route-reflector client and selected as best routes are propagated to all BGP peers (internal and external).Īn IBGP route received from a route-reflector client is sent to all IBGP peers, including the client from which it was received.

Routes received from an IGBP peer that is not a route-reflector client and selected as best routes are propagated to all EBGP peers and all IGBP peers configured as route-reflector clients.

Locally originated routes and routes received from EBGP neighbors and selected as best routes are propagated to all BGP peers (internal and external).

Route Reflector RulesĪ BGP router implementing route reflector functionality propagates BGP routes according to these rules: RFC 4271 defines a new attribute ( cluster list) which can detect route propagation loops within an AS, allowing us to build any IBGP topology we wish as long as we follow a few simple rules.

The next revision of the BGP standard ( RFC 4271) already included references to the BGP Route Reflector functionality defined in RFC4456 and augmented in RFC7606. We retrieved the original textįrom the Internet Archive, cleaned it up, updated it with recent information if necessary, That web site became unreachable in early 2019.

The following text written by Ivan Pepelnjak in 2008 was originally published onĬT3 wiki.