Configuring A Large Scale Bgp Network - 3Com Switch 4800G 24-Port Configuration Manual

390 C 30: BGP C
HAPTER
Configuring a Large
Scale BGP Network
Configuration
Prerequisites
Configuring BGP Peer
Groups
ONFIGURATION
To do...
Configure the number of BGP load
balanced routes
n
The maximum keepalive interval should be one third of the holdtime and no
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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
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the timer command.
Use of the peer keep-all-routes command saves all routing updates from the
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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
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policy without tearing down BGP sessions.
BGP soft reset requires all routers in the network have the route-refresh
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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.
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.
Before configuring this task, you have made peering nodes accessible to each
other at the network layer.
Follow these steps to configure BGP peer groups:
To do...
Enter system view
Enter BGP view
Use the command...
balance number
Use the command...
system-view
bgp as-number
Remarks
Optional
Load balancing is not
enabled by default.
Remarks
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