3Com Switch 8800 Configuration Guide Chapter 16 IP Routing Protocol Overview16-4The Switch 8800 supports the configuration of a series of dynamic routing protocolssuch as RIP, OSPF, IS-IS and BGP, as well as the static routes. In addition, the runningswitch will automatically obtain some direct routes according to the port state and userconfiguration.16.2 Routing Management PolicyFor the Switch 8800, you can configure manually the static route to a specificdestination, and configure dynamic routing protocol to interact with other routers on thenetwork. The routing algorithm can also be used to discover routes. For the configuredstatic routes and dynamic routes discovered by the routing protocol, the Switch 8800implements unified management. That is, the static routes configured by the user aremanaged together with the dynamic routes discovered by the routing protocol. Thestatic routes and the routes learned or configured by different routing protocols can alsobe shared with each other.16.2.1 Routing Protocols and the Preferences of the Corresponding RoutesDifferent routing protocols (as well as the static configuration) may generate differentroutes to the same destination, but not all these routes are optimal. In fact, at a certainmoment, only one routing protocol can determine a current route to a specificdestination. Thus, each of these routing protocols (including the static configuration) isset with a preference, and when there are multiple routing information sources, theroute discovered by the routing protocol with the highest preference will become thecurrent route. Routing protocols and the default preferences (the smaller the value is,the higher the preference is) of the routes learned by them are shown in Table 16-1.In the table, 0 indicates a direct route. 255 indicates any route from unreliable sources.Table 16-1 Routing protocols and the default preferences for the routes learned bythemRouting protocol or route type The preference of the correspondingrouteDIRECT 0OSPF 10IS-IS 15STATIC 60RIP 100OSPF ASE 150OSPF NSSA 150IBGP 256EBGP 256
