![]() When you create a neighbor with the neighbor remote-as statement, an entry is created in the BGP neighbor database for the specified neighbor. header) 26 BGP: 192.168.1.225 rcv OPEN, version 4, holdtime 180 seconds BGP: 192.168.1.225 rcv OPEN w/ OPTION parameter len: 16 BGP: 192.168.1.225 rcvd OPEN w/ optional parameter type 2 (Capability) len 6 BGP: 192.168.1.225 OPEN has CAPABILITY code: 1, length 4 BGP: 192.168.1.225 OPEN has MP_EXT CAP for afi/safi: 1/1 BGP: 192.168.1.225 rcvd OPEN w/ optional parameter type 2 (Capability) len 2 BGP: 192.168.1.225 OPEN has CAPABILITY code: 128, length 0 BGP: 192.168.1.225 OPEN has ROUTE-REFRESH capability(old) for all address-families BGP: 192.168.1.225 rcvd OPEN w/ optional parameter type 2 (Capability) len 2 BGP: 192.168.1.225 OPEN has CAPABILITY code: 2, length 0 BGP: 192.168.1.225 OPEN has ROUTE-REFRESH capability(new) for all address-families BGP: 192.168.1.225 rcvd OPEN w/ remote AS 200 BGP: 192.168.1.225 went from OpenSent to OpenConfirm BGP: 192.168.1.225 went from OpenConfirm to Established Example 2-7 debug Is Used to Observe Vail’s BGP State Changes for Taos as the BGP Session Comes Up Vail# debug ip bgp BGP debugging is on for address family: IPv4 Unicast Vail# BGP: 192.168.1.225 open active, local address 192.168.1.226 BGP: 192.168.1.225 open failed: Connection refused by remote host, open active d elayed 34034ms (35000ms max, 28% jitter) BGP: 192.168.1.225 open active, local address 192.168.1.226 BGP: 192.168.1.225 went from Active to OpenSent BGP: 192.168.1.225 sending OPEN, version 4, my as: 100, holdtime 180 seconds BGP: 192.168.1.225 send message type 1, length (incl. ![]() (The multiprotocol and route refresh capabilities negotiated in this example are discussed in Chapters 6 and 4, respectively.) With capabilities agreed upon, Vail changes Taos’ state from OpenSent to OpenConfirm and then to Established. The two routers then negotiate capabilities. ![]() Then as BGP comes up at Taos, a TCP connection is accepted its state transitions from Active to OpenSent as Vail sends an Open message to begin the BGP session. 8 In the first few lines, Vail is attempting to open a connection to Taos (192.168.1.225) BGP is not yet enabled at Taos, so the attempts fail and Vail shows Taos in Active state. The BGP state changes at Vail can be seen, in Example 2-7, using debug ip bgp. Specify a neighbor and the neighbor’s AS number with neighbor remote-as.įigure 2-23 shows two routers in different autonomous systems, and Example 2-6 shows their EBGP configurations.įigure 2-23 An EBGP Session Is Established Between Taos and Vail Example 2-6 EBGP Configurations for the Routers in Figure 2-23 Taos router bgp 200 neighbor 192.168.1.226 remote-as 100 Vail router bgp 100 neighbor 192.168.1.225 remote-as 200 Establish the BGP process and specify the local AS number with router bgp. Case Study: EBGP PeeringĪ BGP session between routers is configured in two steps: This section takes you step-by-step through the configuration of BGP peering, from the most basic elements to more refined setups. BGP peering configuration, although still a little more involved than most IGP configurations, is not at all difficult. But most of the complexity around BGP involves policy. Because most networking professionals lack in-depth experience with the protocol, it is often viewed as intimidating.īGP configurations can unarguably be complex. And even when BGP is used, the configurations in small ISPs and non-ISP subscribers are usually quite basic. Outside of ISPs, most network administrators deal with BGP far less than with IGPs, if at all. The source of this sentiment is that BGP implementations are rarer than IGP implementations. Many newcomers to BGP approach the protocol with trepidation. ![]() Configuring and Troubleshooting BGP Peering
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