SmartSwitch Router User Reference Manual 73Chapter 6: BGP Configuration GuideSetting the Autonomous System NumberAn autonomous system number identifies your autonomous system to other routers. Toset the SSR’s autonomous system number, enter the following command in Configuremode.The autonomous-system parameter sets the AS number for the router. Specify anumber from 1–65534. The loops parameter controls the number of times the ASmay appear in the as-path. The default is 1.Setting the Router IDThe router ID uniquely identifies the SSR. To set the router ID to be used by BGP, enter thefollowing command in Configure mode.If you do not explicitly specify the router ID, then an ID is chosen implicitly by the SSR. Asecondary address on the loopback interface (the primary address being 127.0.0.1) is themost preferred candidate for selection as the SSR’s router ID. If there are no secondaryaddresses on the loopback interface, then the default router ID is set to the address of thefirst 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 ispreferred over the local address of a point-to-point interface. If the router ID is implicitlychosen to be the address of a non-loopback interface, and if that interface were to godown, then the router ID is changed. When the router ID changes, an OSPF router has toflush all its LSAs from the routing domain.If you explicitly specify a router ID, then it would not change, even if all interfaces were togo down.Configuring a BGP Peer GroupA BGP peer group is a group of neighbor routers that have the same update policies. Toconfigure a BGP peer group, enter the following command in Configure mode:Set the SSR’s autonomous systemnumberip-router global set autonomous-system loops Set the SSR’s router ID ip-router global set router-id Configure a BGP peer group bgp create peer-group type external|internal|igp|routing[autonomous-system ][proto any|rip|ospf|static][interface |all]
