Huawei Quidway S6500 Series Operation Manual page 230

Operation Manual - Routing Protocol
Quidway S6500 Series Ethernet Switches
The router transmitting BGP messages is called a BGP speaker, which receives and
generates new routing information continuously and advertises the information to the
other BGP speakers. When a BGP speaker receives a new route advertisement from
another AS, it will advertise the route, if the route is better than the current route that
has been learned or is a new route, to all the other BGP speakers in the AS.
A BGP speaker calls other BGP speakers peers which exchange information with it and
multiple related peers compose a peer group.
I. Route advertisement policy
In the implementation of Quidway S6500 Series Ethernet Switches, these policies are
used by BGP when advertising routes:
If there are multiple routes available, a BGP speaker only selects the optimum
one.
A BGP only advertises its own route to its peers.
A BPG 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 IBGP
peers.
A BGP speaker advertises the routes obtained from IBGP to its IBGP peers (In
Quidway S6500 Series Ethernet Switches, BGP and IGP are asynchronous.)
Once the connection is set up, a BGP speaker will advertise all its BGP routes to
its peers.
II. Router selection policy
In the implementation of Quidway S6500 Series Ethernet Switches, these policies are
adopted when BGP selects routes:
First discard the routes unreachable to the next hop.
First select the routes with the highest local preference.
First select the routes rooted from the router itself.
First select the routes with the least AS-paths.
First select the routes with the lowest origin.
First select the routes with the lowest MED value.
First select the routes learned from EBGP.
First select the routes advertised by the router with the lowest ID.
6.1.4 BGP peer and peer group
I. Definition of peer and peer group
A BGP speaker calls other BGP speakers peers which exchange information with it and
multiple related peers compose a peer group.
Huawei Technologies Proprietary
6-3
Chapter 6 BGP Configuration