Here's what doc cd says BGP Next-Hop Address Tracking
The BGP next-hop address tracking feature is enabled by default when a supporting Cisco software image is installed. BGP next-hop address tracking is event driven. BGP prefixes are automatically tracked as peering sessions are established. Next-hop changes are rapidly reported to the BGP routing process as they are updated in the RIB. This optimization improves overall BGP convergence by reducing the response time to next-hop changes for routes installed in the RIB. When a best-path calculation is run in between BGP scanner cycles, only next-hop changes are tracked and processed. Default BGP Scanner Behavior BGP monitors the next hop of installed routes to verify next-hop reachability and to select, install, and validate the BGP best path. By default, the BGP scanner is used to poll the RIB for this information every 60 seconds. During the 60 second time period between scan cycles, Interior Gateway Protocol (IGP) instability or other network failures can cause black holes and routing loops to temporarily form. the scanners runs through BGP rib every 60 seconds to detect changes whilst NHAT is event driven and enabled by default with no particular timer I'd also take this chance to ask that this optimisation would be the replacement of the older IGP synchronisation rule which is now disabled?? -- BR Tony > On 30 Nov 2013, at 07:38, Taqdir Singh <[email protected]> wrote: > > Hi Team is my understanding correct on this > > Scan-timer - basically scans all the rib after 60 seconds > NHAT - first it will find out how many next-hops are there..it will then > only scan for nex-hop every 5 seconds and will not walk through whole RIB ? > > -- > > > Thanks & regards, > > Taqdir Singh > Ph: (+91) 8826009496 > _______________________________________________ > Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: > > iPexpert on YouTube: www.youtube.com/ipexpertinc _______________________________________________ Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: iPexpert on YouTube: www.youtube.com/ipexpertinc
