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/31 prefix for BGP

  • 1.  /31 prefix for BGP

    Posted 01-30-2018 20:35

    Can anybody help me with configuration of BGP with /31 IP address



  • 2.  RE: /31 prefix for BGP

    Posted 01-30-2018 20:45
    What issue are you facing ? isn’t it working for you?

    You want ebgp or ibgp config?


  • 3.  RE: /31 prefix for BGP

    Posted 01-30-2018 21:49

    Its just a query , I would to know when and how we use this setup



  • 4.  RE: /31 prefix for BGP

     
    Posted 01-30-2018 21:58

    /31 is basically when you're on point to point & /31 mean you want to save IP address space.

    Can you use the configuration shared above, it for iBGP & for eBGP, change type internal to external.

     

     



  • 5.  RE: /31 prefix for BGP

    Posted 01-31-2018 02:16

    /31 prefix gives you only two addresses (network and broadcast address) for the subnet. You can use these IPs for point to point connectivity. It helps you conserve IP space.



  • 6.  RE: /31 prefix for BGP

    Posted 02-02-2018 22:02

    Using a /31 subnet mask helps conserve your IP address space for point to point links.

    It doubles the number of links that you can number from a given block of IP addresses.

    If you think of large organisations that have hundreds of WAN links but are rapidly running out of address space.

     

    This is especially useful if you have paid for a block of public addresses from your ISP and so you want to utilize as many of them as possible.

     

    Not only can a /31 subnet be used on serial interfaces but it can also be assigned to ethernet interfaces.



  • 7.  RE: /31 prefix for BGP

     
    Posted 01-30-2018 20:47

     

    test@re0# show protocols bgp
    group CPE {
        type internal;
        local-address 60.60.60.2;
        family inet {
            unicast;
        }
        peer-as 44;
        neighbor 60.60.60.1;

     

    test@re0# show interfaces xe-5/3/0
    unit 0 {
        family inet {
            address 60.60.60.2/31;
        }
        family mpls;
    }

     



  • 8.  RE: /31 prefix for BGP

    Posted 02-02-2018 09:34

    @karand, 60.60.60.1 would be on a different subnet from 60.60.60.2. Your neighbor has to be 60.60.60.3 if your IP is 60.60.60.2/31.



  • 9.  RE: /31 prefix for BGP

     
    Posted 02-02-2018 10:02
    Yes, that's right. Thx.