3Com Switch 8800 Advanced Software V5 Configuration Guide

444 CHAPTER 35: BGP CONFIGURATION
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CAUTION:
■ The maximum keepalive interval should be 1/3 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 the filtering policy is configured. The system uses
these updates to rebuild the routing table after a soft reset is triggered.
■ 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.
■ Configured in BGP view, MD5 authentication also applies to the MP-BGP
VPNv4 extension, because the same TCP connection is used.
Configuring a Large
Scale BGP Network
In a large-scale BGP network, configuration and maintenance become difficult due
to so many 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 a BGP community can also help simplify routing policy management,
and a community has much larger management range than a peer group by
controlling routing policies of multiple BGP routers.
To guarantee connectivity between IBGP peers, you need to make them fully
meshed, but it becomes unpractical when there are too many IBGP peers. Using a
route reflector 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 network layer accessible on peering
nodes.
Configuring BGP Peer
Groups
To do so, use the following commands:
To do... Use the command... Remarks
Enter system view system-view -
Enter BGP view bgp as-number -
Configure
an IBGP
peer
group
Create an IBGP peer
group
group group-name [
internal ]
Optional
You can add multiple peers into
the group. The system will
create these peers automatically
and specify the local AS number
as their AS in BGP view.
Add a peer into the
IBGP peer group
peer ip-address group
group-name [
as-number as-number
]