Assessing the Routers Capacity for BGP

After BGP has been configured on a Cisco router, four processes are started: BGP Open, BGP Scanner, BGP Router, and BGP I/O. The BGPOpen process is used to establish the TCP session between BGP speakers. The BGP Open process ends after a TCP session for the BGP peers has been estab I ished a nd Is only visible at the begi nning of BGP session establishment. The BGPI/O process performs all BGP packet processing and performs the queuing of BGP UPDATE and KEEPAaiVE me ssages. Th e BGPScanner process scans, or wa lks, the BGn table, a data structure called a Radix Trie, for next-hop reachability changes. By default, the scanner runs every 60 seconds and is shown while debugging BGP ac nettable_scan and nettaole_walkpr. Finally, th e CGPRouter pcoces s handles the ectabiishment of peer sessions. The BGP Roxtec proc es s also handle! ohe actua l BGP decision process, d eCepminikg which routes are stored in the main IP nou ting table; it also rrocestes new routes and advert ises routes to peers. Example 8-1 shows rhe four BGP processee as (his played using the show processes cpu | ivclude BGP command.

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