Foundation Summary

The Foundation Summary provides a convenient review of many key concepts in this chapter. If you are already comfortable with the topics in this chapter, this summary might help you recall a few details. If you just read this chapter, this review should help solidify some key facts. If you are doing your final prep before the exam, the following lists and tables are a convenient way to review the day before the exam.

The key features of BGP include the following:

  • iBGP neighbors are normally set up using loopback networks and external neighbors are normally set up using connected physical interfaces.

  • BGP neighbors can be configured directly or by using peer groups.

Table 15-2 summarizes the commands covered in this chapter.

Table 15-2. Summary of BGP Commands
router bgp autonomous-system-numberStarts the BGP routing process.
network network-number mask network-maskIdentifies the networks to be advertised by the BGP process.
neighbor {ip-address | peer-group-name} remote-as autonomous-system-numberIdentifies the neighbor with whom the router is synchronizing its routing table and activates a TCP session with the neighbor. It also configures the remote-as option for a peer group.
neighbor {ip-address | peer-group-name} next-hop-selfUsed to force the router to use its own IP address as the next hop when advertising to neighbors.
aggregate-address ip-address mask [summary-only] [as-set]Used to create an aggregate address. The summary-only option advertises the summary, and the as-set option lists the autonomous system numbers that the more specific routes have traversed.
debug ip bgp [dampening | events | keepalives | updates]Enables you to be very specific about the BGP debug parameters.
clear ip bgp {* | address} [soft [in | out]]Resets the session between the neighbors and reestablishes it with the new configuration that has been entered. The soft option does not tear down the sessions, but it resends the updates. The in and out options allow the configuration of inbound or outbound soft updates. The default is for both.
show ip bgp [summary | neighbors]Shows the BGP connections. A network can be specified to retrieve information on the lone network. The summary option will give the status of the BGP connections. The neighbors option gives both TCP and BGP connections.