Network Router User Manual

SmartSwitch Router User Reference Manual 127
Chapter 12: BGP Configuration Guide
Setting the Autonomous System Number
An autonomous system number identifies your autonomous system to other routers. To
set the SSR’s autonomous system number, enter the following command in Configure
mode.
The autonomous-system <num1> parameter sets the AS number for the router. Specify a
number from 1–65534. The loops <num2> parameter controls the number of times the AS
may appear in the as-path. The default is 1.
Setting the Router ID
The router ID uniquely identifies the SSR. To set the router ID to be used by BGP, enter the
following command in Configure mode.
If you do not explicitly specify the router ID, then an ID is chosen implicitly by the SSR. A
secondary address on the loopback interface (the primary address being 127.0.0.1) is the
most preferred candidate for selection as the SSR’s router ID. If there are no secondary
addresses on the loopback interface, then the default router ID is set to the address of the
first interface that is in the up state that the SSR encounters (except the interface en0,
which is the Control Module’s interface). The address of a non point-to-point interface is
preferred over the local address of a point-to-point interface. If the router ID is implicitly
chosen to be the address of a non-loopback interface, and if that interface were to go
down, then the router ID is changed. When the router ID changes, an OSPF router has to
flush all its LSAs from the routing domain.
If you explicitly specify a router ID, then it would not change, even if all interfaces were to
go down.
Configuring a BGP Peer Group
A BGP peer group is a group of neighbor routers that have the same update policies. To
configure a BGP peer group, enter the following command in Configure mode:
Set the SSR’s autonomous system
number.
ip-router global set autonomous-system <num1>
loops <num2>
Set the SSR’s router ID. ip-router global set router-id <hostname-or-IPaddr>
Configure a BGP peer group. bgp create peer-group <number-or-string>
type external|internal|routing
[autonomous-system <number>]
[proto any|rip|ospf|static]
[interface <interface-name-or-ipaddr> |all]