Dell N3200-ON Networking N-Series Switches User Guide version 6.8.0 - Page 1370

Locally-originated routes are added to Accept-RIB-In. Phase 2 of the decision process considers locally-originated routes along with routes received from peers when selecting the best BGP route to each destination. BGP can be configured to originate the same prefix through a network command and through redistribution. Dell Networking BGP creates a different path for each if the path attributes differ. BGP only advertises the prefix with the preferred path. RFC 4271 section 9.2.1.2 specifies "a minimum amount of time that must elapse between successive advertisements of UPDATE messages that report changes within the advertising BGP speaker's own autonomous systems" and refers to this as minASOriginationInterval. RFC 4271 section 10 suggests a default of 15 seconds. Dell Networking BGP does not enforce minASOriginationInterval, but relies on minRouteAdvertisementInterval, which is applied to all advertisements, to dampen flaps of locally-originated routes. Delay and hold timers limit how often phase 2 of the decision process runs. This phase 2 dampening limits route origination, as does IP event dampening when interface flaps would otherwise cause rapid origination. BGP originates a default route to all neighbors if the default-information originate command is given and the default route is among the routes BGP redistributes. Because this default origination depends on redistribution, BGP normally only originates a default if a default is in the routing table. The always option can be configured to relax this requirement. If the routing table does not contain a default route, but the network administrator wants BGP to originate a default route, the administrator can configure a static default route. To prevent the static default route from affecting the local router's forwarding, the default route can be given a preference of 255 (ip route 0.0.0.0 0.0.0.0 next-hop 255) or it can be configured as a reject route (ip route 0.0.0.0 0.0.0.0 Null0). BGP can also originate a default to a specific neighbor using neighbor default-originate. This form of default origination does not install a default route in the BGP routing table (it will not appear in show ip bgp), nor does it install a default route in the Adj-RIB-Out for the update group of peers so configured (it will not appear in show ip bgp neighbor advertised-routes). A neighbor specific default has no MED and the Origin is IGP. A neighborspecific default is only advertised if the Adj-RIB-Out does not include a 1370 BGP