Dell MX5108n OS10 Enterprise Edition User Guide for PowerEdge MX IO Modules Re - Page 281

The Local-AS does not prepend the updates with the AS number received from the EBGP peer if you use the no prepend command. If you do not select no prepend, the default, the Local-AS adds to the first AS segment in the AS-PATH. If you use an inbound route-map to prepend the AS-PATH to the update from the peer, the Local-AS adds first. If Router B has an inbound route-map applied on Router C to prepend 65001 65002 to the AS-PATH, these events take place on Router B: • Receive and validate the update. • Prepend local-as 200 to AS-PATH. • Prepend 65001 65002 to AS-PATH. Local-AS prepends before the route map to give the appearance that the update passed through a router in AS 200 before it reaches Router B. Configure border gateway protocol BGP is disabled by default. To enable the BGP process and start to exchange information, assign an AS number and use commands in ROUTER-BGP mode to configure a BGP neighbor. BGP neighbor All BGP neighbor changes are logged adjacency changes Fast external fallover Enabled Graceful restart Disabled Local preference 100 4-byte AS Enabled MED 0 Route flap dampening parameters • half-life = 15 minutes • max-suppress-time = 60 minutes • reuse = 750 • suppress = 2000 Timers • keepalive = 60 seconds • holdtime = 180 seconds Add-path Disabled Enable BGP BGP is disabled by default. The system supports one AS number - you must assign an AS number to your device. To establish BGP sessions and route traffic, configure at least one BGP neighbor or peer. In BGP, routers with an established TCP connection are called neighbors or peers. After a connection establishes, the neighbors exchange full BGP routing tables with incremental updates afterward. Neighbors also exchange the KEEPALIVE messages to maintain the connection. You can classify BGP neighbor routers or peers as internal or external. Connect EBGP peers directly, unless you enable EBGP multihop - IBGP peers do not need direct connection. The IP address of an EBGP neighbor is usually the IP address of the interface directly Layer 3 281