BGP
Routing
Information Bases (RIBs)
RIBs contain only BGP specific routing information. The
BGP tables are used to store information about BGP paths. This information
includes the best path to each destination network (used for local routing),
the information to send to other BGP peers, and information obtained from other
bGP peers. After BGP has selected the best path to a network, that path is
added to the main routing table.
Each BGP speaker maintains one Adj-RIB-In and Adj-RIB-Out
per BGP peer relationship. The Adj-RIB-In table stores unprocesses
BGPinformation learned from other BGP peers. The information contained in this
table is used to determine the best path to the destination network, based on
its BGP attributes, using BGP route selection process. Adj-RIB-Out contains the
information to be sent to other BGP peers.
After the local BGP decision process has finished
selecting the best path to each destination network, information is stored in
the local BGP table, which is known as the Loc-RIB. Loc-RIB stores
informationabout paths that conform to the locally configured BGP policies. The
BGP speaker learns these routes by means of local BGP configuration. There is
only one Loc-RIB per router
"The BGP/IDRP identifier must be the same as the
OSPF router ID at all times that the router is up." If the OSPF and BGP
router IDs do not match, BGP cannot synchronize with OSPF, causing BGP not to
advertise any unsynchronized routes to any peers.
If BGP synchronization is not disabled, and an IGP
protocol is not providing routing information, the BGP speaker does not use or
propagate routes that it does not know how to reach.
To provide a consistent view of an AS to upstream BGP
peers, by default, AS bordering routers do not advertise unsynchronized routes
learned through I-BGP sessions to E-BGP peers. This is due to the rule of
synchronization. BGP synchronization allows I-BGP peers to provide upstream peers
with a consistent view of their networks. Because I-BGP-speaking routers that
have synchronized BGP and IGP routing tables assume that all other internal
peers have the same routing tables, there should not be any unsynchronized
routes. As long as all the speakers in an I-BGP network are fully meshed and
have a consistent view of the BGP network, IGP to BGP synchronizing can be
disabled.
BGP Capabilities Code
Notification Messages
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