bgp route-refresh/soft reconf/clear ...

Hello,

I was testing modifying route-maps on bgp announces and fond that i don't need to issue "clear " commands.
Someone can explain or give me a link to why is working and no more need to force updates.


Two routers, eBGP between them, R1 is setting, R2 is receiving.

I set on R1 a community 1:1, on R2 i see it.
I add another community on R1, i see them on R2.
I put a AS-prepend, i get it on R2.

All this without deleting the route-map and re-create, and without "clear bgp soft".



My expected behaviour was to nothing gets updated alone.

Do the IOS evolved and at each bgp scan he re-run through the route-maps or something else????
The versions are 12.2SRD on 7600 SUP720.

Thanks for info.



Ciprian

Comments

  • Hi!

    Could you post a config snippet and some show output maybe? Thatll be very cool. Then we can check about the sequence the bgp scanner is doing the updates.

    Regards!

    Markus

  • peetypeety ✭✭✭

    Cisco snuck that into the high-end platforms a few years back.

    Folks here aren't necessarily going to be familiar with your question...7600 isn't likely to be in their labs.

  • Folks here aren't necessarily going to be familiar with your question...7600 isn't likely to be in their labs.

    But thats good because one can learn something new :). 7600 platform is daily business for me, I control about 50 of them.

     

    EDIT: Exact IOS version would be cool including feature set; e.g. 12.2(33)SRD5 adv ip services.

     

    Regards!

    Markus

  • Standard configs, R1-R2-R3
    i test also a retag on R2 in acordance with what i get from R1:

    R1:
    router bgp 1234
     bgp log-neighbor-changes
     no auto-summary
     !
     address-family ipv4 vrf Bleu
      network 4.0.0.13 mask 255.255.255.255



      neighbor 4.103.1.3 remote-as 65003
      neighbor 4.103.1.3 activate
      neighbor 4.103.1.3 send-community
      neighbor 4.103.1.3 soft-reconfiguration inbound
      neighbor 4.103.1.3 route-map TAG out
     exit-address-family



    !
    route-map TAG permit 10
     set community 13:95 13:1195
    !
    route-map TAG permit 20
    !

    R2:
    router bgp 65003
     bgp router-id 6.0.0.3
     bgp log-neighbor-changes
     bgp update-delay 30
     bgp graceful-restart restart-time 120



     bgp graceful-restart stalepath-time 360
     bgp graceful-restart
     timers bgp 5 15
     !
     address-family ipv4 vrf Bleu
      redistribute static
      redistribute connected
      neighbor 4.103.1.13 remote-as 1234



      neighbor 4.103.1.13 activate
      neighbor 4.103.1.13 send-community
      neighbor 4.103.1.13 soft-reconfiguration inbound
      neighbor 4.103.1.13 route-map TAG-IVT-IN in
     exit-address-family
     !
    ip community-list expanded IVT-Lien1 permit [0-9]+:85



    ip community-list expanded IVT-Lien2 permit [0-9]+:95

    route-map TAG-IVT-IN permit 10
     match community IVT-Lien1
     set community 3215:85 65012:13 additive
    !        
    route-map TAG-IVT-IN permit 20



     match community IVT-Lien2
     set community 3215:95 45012:13 55012:13 additive
    !        
    route-map TAG-IVT-IN permit 30
     set community 5012:13 additive
    !        

    R3: just a ebgp peer without any routemap



    Cheers,

    Ciprian







    On Mon, Feb 27, 2012 at 3:02 PM, markus.wirth <[email protected]> wrote:

    Hi!

    Could you post a config snippet and some show output maybe? Thatll be very cool. Then we can check about the sequence the bgp scanner is doing the updates.

    Regards!

    Markus







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  • Hi!

    Config looks good for me at first sight.

    I think this is related to BGP Soft reset enhancement? Never heard it before but kind of matches your question here.

     

    Link:

    http://www.cisco.com/en/US/products/ps6599/products_data_sheet09186a0080087b3a.html 

     

    Important Lines:

    Previously, in order to reconfigure the inbound routing table, both the local BGP router and the BGP peer first needed to be configured to store incoming routing policy updates using the neighbor soft-reconfiguration command. Additional resources, particularly memory, were required to store the inbound routing table updates. The clear ip bgp command could then initiate the soft reset, which generated a new set of inbound routing table updates using the stored information.

    This feature provides an additional method for soft reset that allows the dynamic exchange of route refresh requests and routing information between BGP routers, and the subsequent re-advertisement of the respective outbound routing table. Soft reset using the route refresh capability does not require preconfiguration and consumes no additional memory resources. 

     

    Maybe that hits your question here.

    Regards!

    Markus

  • Hi Ciprian,

    This hapening due to soft-reconfiguration inbound.

    What bgp soft-reconfiguration does?

    As soon as you make changes in routing policies, you should reset/clear
    the BGP peering to apply the policies(either hard reset or soft, soft is
    recommended). clear ip bgp * soft in|out. BGP neighbor soft-reconfiguration command directed the Cisco
    IOS software in the local BGP router to store all received (inbound)
    routing policy updates without modification.

    I hope it cleared now:)

  • peetypeety ✭✭✭

    Hi Ciprian,

    This hapening due to soft-reconfiguration inbound.

    What bgp soft-reconfiguration does?

    As soon as you make changes in routing policies, you should reset/clear
    the BGP peering to apply the policies(either hard reset or soft, soft is
    recommended). clear ip bgp * soft in|out. BGP neighbor soft-reconfiguration command directed the Cisco
    IOS software in the local BGP router to store all received (inbound)
    routing policy updates without modification.

    I hope it cleared now:)

    Um, no.  This has nothing to do with soft-reconfiguration.  This has to do with changes inside IOS, causing BGP to trigger an automatic outbound clear and a route refresh request when the routing policy has been modified.  It's new, it's not well publicized, and it has nothing to do with 'clear' commands or neighbor options.

  • :) nice mail
    thank's all, i'll do some testing and let you know


    On Tue, Feb 28, 2012 at 3:28 PM, peety <[email protected]> wrote:

    imageNarayan.Neupane:


    Hi Ciprian,

    This hapening due to soft-reconfiguration inbound.

    What bgp soft-reconfiguration does?

    As soon as you make changes in routing policies, you should reset/clear
    the BGP peering to apply the policies(either hard reset or soft, soft is
    recommended). clear ip bgp * soft in|out. BGP neighbor soft-reconfiguration command directed the Cisco
    IOS software in the local BGP router to store all received (inbound)
    routing policy updates without modification.

    I hope it cleared now:)

    Um, no.  This has nothing to do with soft-reconfiguration.  This has to do with changes inside IOS, causing BGP to trigger an automatic outbound clear and a route refresh request when the routing policy has been modified.  It's new, it's not well publicized, and it has nothing to do with 'clear' commands or neighbor options.




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