3Com Switch 7750 Configuration Guide Guide

342 CHAPTER 36: BGP CONFIGURATION
c
CAUTION:
■ A router must be assigned a router ID in order to run BGP protocol. A router ID
is a 32-bit unsigned integer. It uniquely identifies a router in an AS.
■ The router ID can be manually configured. If you do not specify a router ID, the
system automatically choose the IP address of one of its interfaces as the router
ID. In this case, the least loopback interface IP address is most preferred. If no
loopback interface is configured, the least interface IP address is chosen as the
router ID. For network reliability consideration, you are recommended to
configure the IP address of a loopback interface as the router ID.
■ In order for route updating packets being sent even if problems occur on
interfaces, you can configure the source interfaces of route update packets as a
loopback interface.
■ Normally, EBGP peers are connected through directly connected physical links.
If no such link exists, you need to use the peer ebgp-max-hop command to
allow the peers to establish multiple-hop TCP connections between them.
Configuring the Way
to Advertise/Receive
Routing Information
Configuration
Prerequisites
Make sure the following operation is performed before configuring the way to
advertise/receive BGP routing information.
■ Enabling the basic BGP functions
Make sure the following information is available when you configure the way to
advertise/receive BGP routing information.
■ The aggregation mode, and the aggregated route.
■ Access list number
■ Filtering direction (advertising/receiving) and the route policies to be adopted.
■ Route dampening settings, such as half-life and the thresholds.
Importing Routes With BGP employed, an AS can send its interior routing information to its
neighbor ASs. However, the interior routing information is not generated by BGP,
it is obtained by importing IGP routing information to BGP routing table. Once IGP
routing information is imported to BGP routing table, it is advertised to BGP peers.
Allow routers that belong to
non-directly connected
networks to establish EBGP
connections.
peer group-name
ebgp-max-hop [hop-count ]
Optional
By default, routers that
belong to two non-directly
connected networks cannot
establish EBGP connections.
You can configure the
maximum hops of EBGP
connection by specifying the
hop-count argument.
Table 273 Configure basic BGP functions
Operation Command Description