390 CHAPTER 30: BGP CONFIGURATION
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■ 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.
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.
Configuration
Prerequisites
Before configuring this task, you have made peering nodes accessible to each
other at the network layer.
Configuring BGP Peer
Groups
Follow these steps to configure BGP peer groups:
Configure the number of BGP load
balanced routes
balance number Optional
Load balancing is not
enabled by default.
To do… Use the command… Remarks
To do… Use the command… Remarks
Enter system view system-view -
Enter BGP view bgp as-number -
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