3Com 3.01.01 Switch User Manual


 
BGP 127
Route Advertisement Policy
In the Switch 8800, BGP uses the following policies when it advertises routes:
If there are multiple routes available, a BGP speaker only selects the optimum
one.
A BGP speaker only advertises its own route to its peers.
A BGP speaker advertises the routes obtained from EBGP to all its BGP peers
(including EBGP and IBGP peers).
A BGP speaker does not advertise the routes obtained from IBGP to its other
IBGP peers.
Once the connection is set up, a BGP speaker will advertise all its BGP routes to
its peers.
Router Selection Policy
In the Switch 8800, BGP uses the following policies when it selects routes:
Discard the routes from an unreachable or unknown next hop.
Select the routes with the highest local preference.
Select the routes that originate at the router itself.
Select the routes with the lowest number of AS-paths.
Select the routes with the lowest origin.
Select the routes with the lowest MED value.
Select the routes learned from EBGP.
Select the routes advertised by the router with the lowest ID.
BGP Peers and Peer
Groups
A BGP speaker calls other BGP speakers, peers, when they exchange information.
Multiple related peers compose of a peer group.
In the Switch 8800, a BGP peer must belong to a peer group. If you want to
configure a BGP peer, you first need to create a peer group and then add a peer
into that group.
BGP peer group feature can simplify user configuration and improve route
advertisement efficiency. When added into a peer group, a peer inherits all the
configuration of the group.
If the configuration of a peer group changes, the configuration of its member
peers also changes. Some attributes can be configured to a particular member
peer by specifying its IP address. The attributes configured in this way have a
higher priority than those configured for a peer group. Note that all member peers
must use the same update policy as its group, but may use a different ingress
policy.
Configuring BGP BGP configuration includes:
Enabling BGP
Entering Extended Address Family View
Configuring Basic Features for a BGP Peer