BGP Scan process

Bit of an open ended question this one - Is there any value tuning bgp scan-time now that most processes are now event driven within BGP?

Comments

  • Hi,

       I don't actually understand your question. Can you rephrase?

    Good luck with your studies!

  • peetypeety ✭✭✭

    Rule #1: don't assume it's event-driven.  Test to be sure.

    I come from an ISP background, and would say that tuning the scan time only increases the odds that a luser will complain about pings to the routers and traceroutes through the routers show "an obvious problem that is impacting my <fill in the blanks with some useless tool>".

  • Hi,

       I don't actually understand your question. Can you rephrase?

    Good luck with your studies!

    Hi Cristian

    In the old days the scanner process would confirm that nexthop were available amongst other things.  Clearly if you lost your next hop there would be long wait (60 seconds) for the scanner process to get arround to sorting this out.  This process was CPU intensive so care had to taken not reduce this timer to a low value.

    For some time IOS has improved the status quo by allowing the above process to be event driven e.g. extenal failover when a link goes down, fall over and next hop address tracking.

    With all of these feature in mind is there any value tuning the scanner process?

    I hope this makes more sense

     

  • In the old days the scanner process would confirm that nexthop were available amongst other things.  Clearly if you lost your next hop there would be long wait (60 seconds) for the scanner process to get arround to sorting this out.  This process was CPU intensive so care had to taken not reduce this timer to a low value.

    For some time IOS has improved the status quo by allowing the above process to be event driven e.g. extenal failover when a link goes down, fall over and next hop address tracking.

    With all of these feature in mind is there any value tuning the scanner process?

    I hope this makes more sense

     

     


    hi welshydragon,
    According to CCO cmd ref, when "bgp nexthop" is configured, IOS does not accept "bgp scan-time" command. So, my impression is there is no point tuning bgp scan time while event driven update is used.
    http://www.cisco.com/en/US/docs/ios/iproute_bgp/command/reference/irg_bgp1.html#wp1116049

  • hi welshydragon,
    According to CCO cmd ref, when "bgp nexthop" is configured, IOS does not accept "bgp scan-time" command. So, my impression is there is no point tuning bgp scan time while event driven update is used.
    http://www.cisco.com/en/US/docs/ios/iproute_bgp/command/reference/irg_bgp1.html#wp1116049

    Very interesting - failed by the doc again!

    Your link shows the pertinent information about scan time.

    I have been reading the command reference for BGP over the last couple of days via PDF - mine was dated June 2010 and didn't include the following paragragh -

    While bgp nexthop address tracking (NHT) is enabled for an address family, the bgp scan-time
    command will not be accepted in that address family and will remain at the default value of 60 seconds.
    NHT must be disabled before the bgp scan-time command will be accepted in either router mode or
    address family mode.

    Whereas as lastest version of this document dated March 2011 (for the whole document - July 2011 for the relevant chapter) does include this!

    Hence my dumb question.  I use PDFs as I spend a lot of time travelling - unreliable 3G on the train - so PDF is the best option assuming it's not out of date.

    Thanks for spotting this :-)

    The other point is NHT is enabled by default so the point is you CAN'T change the scan time - unless of course you disable NHT!

  • Hi welshydragon,

       I know how the feature works, i just did no get your question meaning. Thanks for clarification anyways, and yes it is always good to look in the Conmmand Reference from time to time.:) Alexander found an excelent detail.

    Good luck with your studies!



  • We Don't Need No Stinking BGPs!

     

    http://www.youtube.com/watch?v=gx6TBrfCW54

     

     

     

     

     



     

     


     

     

     

  • Hi Rauta,

       I have to say your posts are by far the most brain consuming ones :)

    Good luck with your studies!

  • Funny you, i was to young back then to remember him!

Sign In or Register to comment.