Configuring Bgp Update Flows; Configuring Bgp Path Selection Algorithm; Bgp Path Selection Algorithm - Motorola BSR 2000 Configuration And Management Manual

BSR 2000 Configuration and Management Guide

Configuring BGP Update Flows

BGP update messages are exchanged between BGP peers to determine how a BGP
router updates route entries in its routing table. Use BGP commands to modify the
information in BGP updates sent out by a router to one or more of its peers.
To control the flow of BGP updates, configure the following:

Configuring BGP Path Selection Algorithm

BGP selects the best possible path for a route and installs it in its route table. If only
one route exists for a specific destination, BGP selects that route, because, by
definition, it is the best route. If multiple routes exist, BGP uses the BGP Path
Selection Algorithm to select the best path.

BGP Path Selection Algorithm

The BGP path selection process uses the following sequential criteria to select a path:
1. If the next hop is inaccessible, BGP does not consider the route. For this reason, it
2. If synchronization is enabled, the path is internal, and the route is not in an IGP.
3. BGP uses the route that was locally originated, using either the network or
4. BGP uses the path with the largest weight, a value ranging from 0 to 65535. The
5. BGP uses the route with the largest local preference. Define a particular path as
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Filtering of sent and received updates
BGP path selection options
is important to have an IGP route to the next hop.
BGP ignores the route.
aggregate-address command, or through redistribution from an IGP.
administrative weight is local to the router. BSR originating paths have a weight
of 32768 by default; other paths, from peers, have a default weight of 0. To
configure specific neighbors as preferred for most traffic, use the neighbor
weight command to assign a higher weight to all routes learned from that
neighbor. You can also assign weights based on AS path access lists. A given
weight becomes the weight of the route, if the AS path is permitted by the access
list. Any number of weight filters are allowed.
more preferable or less preferable than other paths by changing the default local
preference value of 100. To assign a different default local preference value, use
the bgp default local-preference command.
MGBI
Release 1.0
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