H3C SecPath F1800-A Operation Manual page 300

Operation Manual - Network and Routing Protocol
H3C SecPath F1800-A Firewall
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 that exchange information with it peers and
multiple related peers compose a peer group.
I. Policies for BGP to Advertise Routes
BGP follows the policies below when advertising routes.
If there are several optional routes, BGP speaker only selects the optimal one.
BGP speaker only advertises the route it uses to the peers.
BGP speaker advertises the route received from EBGP to all the BGP peers,
including EBGP and IBGP peers.
BGP speaker does not advertise the route received from IBGP to the IBGP
peers.
BGP speaker does not advertise the route received from IBGP to the EBGP
peers (in VRP, the synchronous relationship does not exist between IGP and
BGP).
On establishing a peer connection, BGP speaker advertises all the BGP routes
to the peer.
II. Policies for BGP to Select Routes
BGP uses the following policies to select routes.
First discard the route whose next hop is unreachable.
Select the route with the highest local-preference.
Select the route initially sent by the local router.
Select the route passing the least number of ASs (AS-Path).
Select the route with the lowest origin type.
Select the route with the lowest MED.
Select the route learned from EBGP.
If the load balancing is configured and there are multiple external routes to an AS
or AS confederation, select several routes to perform the load balancing based
on the number of configured routes.
Select the route advertised by the router with the lowest BGP ID.
6.1.4 MBGP
I. Introduction to MBGP
The traditional BGP-4 can only manage the routing information of IPv4 and has
limitation in inter-AS routing when used in the application of other network layer
protocols (such as IPv6 etc).
Chapter 6 BGP/MBGP Configuration
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