SmartSwitch Router User Reference Manual 97Chapter 6: BGP Configuration GuideNotes on Using CommunitiesWhen originating BGP communities, the set of communities that is actually sent is theunion of the communities received with the route (if any), those specified in group policy(if any), and those specified in export policy (if any).When receiving BGP communities, the update is only matched if all communitiesspecified in the optional-attributes-list option of the ip-router policy create command arepresent in the BGP update. (If additional communities are also present in the update, itwill still be matched.)Local_Pref Attribute ExampleFigure 7 shows a BGP configuration that uses the BGP local preference (Local_Pref)attribute in a sample BGP configuration with two autonomous systems.The local preference is not set directly in the CLI, but rather is a function of the GateDpreference and setpref metric. The setpref option allows GateD to set the local preferenceto reflect GateD's own internal preference for the route, as given by the global protocolpreference value. The setpref option may be used with routing or internal type groups.BGP routes with a larger Local_Pref are preferred.The formula used to compute the local preference is as follows:Local_Pref = 254 – (global protocol preference for this route) + set preference metricNote: A value greater than 254 will be reset to 254. GateD will only send Local_Prefvalues between 0 and 254.In a mixed GateD and non-GateD network, the non-GateD IBGP implementation maysend Local_Pref values that are greater than 254. When operating a mixed network of thistype, you should make sure that all routers are restricted to sending Local_Pref values inthe range metric to 254.
