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I have a weird question

  • 1.  I have a weird question

    Posted 16 days ago
    I have two BGP sessions. I need to disable one of them based on whether the other is up or not?

    Can I do that ?

    thanks a lot in advance !!


  • 2.  RE: I have a weird question

    Posted 16 days ago
    Hello, 

    Yes. You can. Using the command, show bgp summary check which BGP session you wanna disable. 

    If you are unsure about the impact, I would suggest you to perform this during a maintenance window or off-production hours.

    ------------------------------
    ***𝑫𝒐 𝒎𝒂𝒓𝒌 𝒕𝒉𝒊𝒔 𝒂𝒏𝒔𝒘𝒆𝒓 𝒂𝒔 𝑺𝒐𝒍𝒗𝒆𝒅, 𝒊𝒇 𝒊𝒕 𝒂𝒅𝒅𝒓𝒆𝒔𝒔𝒆𝒔 𝒚𝒐𝒖𝒓 𝒊𝒔𝒔𝒖𝒆***

    𝕽𝖊𝖌𝖆𝖗𝖉𝖘,
    𝖓𝖔𝖔𝖇 𝖒𝖆𝖘𝖙𝖊𝖗.
    ------------------------------



  • 3.  RE: I have a weird question

    Posted 16 days ago
    thanks a lot !!

    But I need this automatically.  Kind of ODD.


  • 4.  RE: I have a weird question

    Posted 16 days ago

     

     

    Hi , if you want to use second session as backup only , you can configure Conditional Advertisement Enabling Conditional Installation of Prefixes.

    This will allow you to announce/receive prefixes to second bgp neigbour only if some tested prefix (for example 0.0.0.0/0 ) received from primary peer is missing.

     


    Juniper Business Use Only






  • 5.  RE: I have a weird question

    Posted 16 days ago
    Actually I am looking for a workable approach to the following issue I am having.

    As I can't LAG the L2 switch for some reason and also I can't block the L2 via STP,  I will get a loop for two EVPN sessions.  A BUM traffic from the right site will have two copies into L2 switch, the L2 switch forward BUM traffic to the other VTEP to send it back to VTEP on the right.

    I am wondering whether any way can disable one EVPN session to keep only one session UP,  if the session is down, then the second session automatically comes up. Kind of crazy, right ?

    I am working on some event policy to see if I can achieve it.

    If BGP has some built-in feature to achieve this, that will save me.

    thanks a lot !!


  • 6.  RE: I have a weird question

    Posted 16 days ago

    Hmm, that is VERY bad idea.

    1. what you will do if client will send traffic to switch where bgp session is down ? in this case all traffic will be dropped
    2. switching between on/off bgp session will take too much time , i think 10s of seconds

     

    Thate are 2 options for you

    1. mc-lag/esi-lag
    2. controlling link state on CE device. enable only one link at any time.

     

    Why you can not use lag ?

     


    Juniper Business Use Only






  • 7.  RE: I have a weird question

    Posted 16 days ago
    thanks a lot !!

    Unable to use LAG is because it is a critical network for a long time, no possibility to change, also the switches are old and non juniper products.


  • 8.  RE: I have a weird question

    Posted 14 days ago

    2 questions/comments

    1 - why can't you run STP on the CE switch?

    2 - for multi-homed CE like yours, a nice capability of EVPN is supposed to allow for active/active forwarding and deal with loop prevention at the PE



    ------------------------------
    Aaron Gould
    Senior Network Engineer
    aaron@gvtc.com
    https://www.linkedin.com/in/agould123/
    ------------------------------



  • 9.  RE: I have a weird question

    Posted 14 days ago
    thanks !!
    As the both links need to be accessible from the remote sites.
    The switches are not allowed to be change for some historically reasons.

    I am trying to use event-policy to disable one of BGP sessions.