Riverstone Networks WICT1-12 - Manual (Page 261)

Riverstone Networks RS Switch Router User Guide Release 8.0 16-3
BGP Configuration Guide Basic BGP Tasks
If you do not explicitly specify the router ID, then an ID is chosen implicitly by the RS. A secondary address on the
loopback interface (the primary address being 127.0.0.1) is the most preferred candidate for selection as the 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 RS 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.
16.2.3 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:
where:
peer-group
<number-or-string>
Is a group ID, which can be a number or a character string.
type
Specifies the type of BGP group you are adding. You can specify one of the following:
external
In the classic external BGP group, full policy checking is applied to all incoming and
outgoing advertisements. The external neighbors must be directly reachable through one of
the machine's local interfaces.
routing
An internal group which uses the routes of an interior protocol to resolve forwarding
addresses. Type Routing groups will determine the immediate next hops for routes by using
the next hop received with a route from a peer as a forwarding address, and using this to
look up an immediate next hop in an IGP’s routes. Such groups support distant peers, but
need to be informed of the IGP whose routes they are using to determine immediate next
hops. This implementation comes closest to the IBGP implementation of other router
vendors.
autonomous-system
<number>
Specifies the autonomous system of the peer group. Specify a number from 1 to 65535.
proto
Specifies the interior protocol to be used to resolve BGP next hops.
interface
<name-or-IPaddr> |
all
Interfaces whose routes are carried via the IGP for which third-party next hops may be used instead. Use
only for type Routing group. Specify the interface or
all
for all interfaces.
Configure a BGP peer group.
bgp create peer-group
<number-or-string>
type external|routing
[autonomous-system
<number>
] [proto any|rip|ospf|static]
[interface
<interface-name-or-ipaddr>
|all]