Configuring A Large Scale Bgp Network; Configuring Bgp Peer Groups - H3C S5500-EI series Operation Manual

Operation Manual – IPv4 Routing
H3C S5500-EI Series Ethernet Switches
Note:
The maximum keepalive interval should be one third of the holdtime and no less
than 1 second. The holdtime is no less than 3 seconds unless it is set to 0.
The intervals set with the peer timer command are preferred to those set with the
timer command.
Use of the peer keep-all-routes command saves all routing updates from the peer
regardless of whether any filtering policy is configured. The system uses these
updates to rebuild the routing table after a soft reset.
Performing BGP soft reset can refresh the routing table and apply the new policy
without tearing down BGP sessions.
BGP soft reset requires all routers in the network have the route-refresh capability. If
not, you need use the peer keep-all-routes command to keep all routing
information from a BGP peer to perform soft reset.

5.7 Configuring a Large Scale BGP Network

In a large-scale BGP network, configuration and maintenance become difficult due to
large numbers of BGP peers. In this case, configuring peer groups makes management
easier and improves route distribution efficiency. Peer group includes IBGP peer group,
where peers belong to the same AS, and EBGP peer group, where peers belong to
different ASs. If peers in an EBGP group belong to the same external AS, the EBGP
peer group is a pure EBGP peer group, and if not, a mixed EBGP peer group.
Configuring BGP community can also help simplify routing policy management, and a
community has a much larger management scope than a peer group by controlling
routing policies of multiple BGP routers.
To guarantee the connectivity between IBGP peers, you need to make them fully
meshed. But it becomes unpractical when there are large numbers of IBGP peers.
Configuring route reflectors or confederation can solve it. In a large-scale AS, both of
them can be used.
5.7.1 Configuration Prerequisites
Before configuring this task, you have made peering nodes accessible to each other at
the network layer.

5.7.2 Configuring BGP Peer Groups

Follow these steps to configure BGP peer groups:
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Chapter 5 BGP Configuration