BGP protocol Introduction

BGP protocol overview * BGP autonomous system-AS is a group of centrally managed routers that use the same internal gateway protocol and unified measurement values in AS internal routing groups, and use the external gateway protocol to route the group to other. -- BGP is used to connect to the autonomous system and provide routes between AS-. * BGP database-neighbor table * List of BGP peers-BGP forwarding database * all networks learned from peers * contains multiple paths to the destination Network * multiple attributes of BGP paths-IP route Selection table * optimal route to destination Network * peer (neighbor) * The router that sends the BGP message is known as the BGP Speaker (BGP Speaker) * The BGP Speaker exchange messages with each other as the BGP peer) * EBGP neighbor * Is In The BGP peer of different, normally, the EBGP peer is physically directly connected * routes obtained by BGP speakers from the EBGP peer are advertised to all of its BGP peers (including EBGP and IBGP) * I BGP peers * The BGP peer in the same AS is an IBGP peer. Routes learned from the IBGP peer are not advertised to other IBGP peers. * How does the AS prevent loops? By default, Routes learned by IBGP peers are not sent to their IBGP peers, therefore, they need to be fully interconnected-are the routes obtained from IBGP published to its EBGP peer and BGP synchronized? * How to Avoid black holes? ---- Synchronization rules-synchronization rule definition: * BGP does not allow direct publishing of Routes learned from the IBGP peer to the EBGP peer, unless these routes have been IGP (Note: IGP) learn -- after synchronization is enabled, it will be published to the EBGP peer * EBGP route (BGP Route learned from the external AS) only when IGP knows this IBGP route) the Management Distance of is 20 * IBGP route (the route learned from the AS system). The management distance is 200 --------------------------------------------- neighbor table: contains the neighbor with which the BGP connection is established. Run the show ip bgp summa command. Ry can view the forwarding table: all the routes learned from the neighbors are added to the BGP forwarding table. Run the show ip bgp command to view the route table: the BGP route Selection Process selects the optimal route entry to each network from the BGP forwarding table and adds it to the routing table. Run the show ip route bgp command to view the route ------------------------------------- * BGP Message Type -- open: used to establish the initial BGP connection. (Including hold-time, router-id) -- Keepalive: periodically exchanges these messages between peers to keep the session valid. (60 seconds by default) -- Update: these messages are used between peers to exchange network-layer accessibility information. -- Notification: these messages are used to notify users of errors. **************************************** * ******************* You must manually specify the neighbor ************* **************************************** ********