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  • 1.  BGP Advertising

    Posted 04-12-2021 13:43
    Hello,

    I have 3 peers that I BGP with.  I am needing to remove advertising for certain networks to one BGP peer. I have created some policy options that I think may work but just want some clarity on them. ISP's 1 and 2 get full networks advertised from BGP, while ISP 3 will only be getting certain networks advertised.

    protocols {
    bgp {
    group internet-peers {
    type external;
    family inet {
    unicast;
    multicast;
    }
    peer-as 5XXX4;
    multipath;
    neighbor 4.XXX.XXX.173 {
    description "ISP 1"
    export adv-supernets;
    peer-as 3XX6;
    }
    neighbor 64.XXX.XXX.197 {
    description "ISP 2"
    export adv-supernets;
    peer-as 2XXX2;
    }
    neighbor 206.XXX.XXX.253 {
    description "ISP 3"
    export adv-supernets-ISP-3;
    peer-as 1XXX1;
    }

    policy-options {
    prefix-list all-supernets {
    137.XXX.XX4.0/24;
    137.XXX.XX5.0/24;
    137.XXX.X8.0/22;
    192.XXX.X2.0/20;
    208.XXX.40.0/24;
    208.XXX.41.0/24;
    208.XXX.42.0/24;
    208.XXX.43.0/24;
    208.XXX.44.0/24;
    208.XXX.45.0/24;
    prefix-list external-supernets {
    23.XXX.XX.0/24;
    137.XXX.XX6.0/24;
    137.XXX.XX7.0/24;
    192.XXX.X8.120/30;
    192.XXX.X10.0/24;
    198.XXX.XX3.0/24;
    198.XXX.XX1.0/24;
    198.XXX.XX4.0/24;
    208.XXX.46.0/24;
    208.XXX.47.0/24;
    prefix-list external-supernets-ISP-3 {
    137.XXX.XX6.0/24;
    137.XXX.XX7.0/24;
    208.XXX.46.0/24;
    208.XXX.47.0/24;

    policy-statement adv-supernets {
    term 10 {
    from {
    protocol static;
    prefix-list-filter all-supernets exact;
    }
    then accept;
    }
    term 15 {
    from {
    protocol bgp;
    prefix-list-filter external-supernets exact;
    }
    then accept;
    }
    term 20 {
    then reject;
    }
    }
    policy-statement adv-supernets-ISP-3 {
    term 10 {
    from {
    protocol static;
    prefix-list-filter all-supernets exact;
    }
    then accept;
    }
    term 15 {
    from {
    protocol bgp;
    prefix-list-filter external-supernets-ISP-3 exact;
    }
    then accept;
    }
    term 20 {
    then reject; 

    Thank you

    ------------------------------
    Jack Gonzales
    ------------------------------


  • 2.  RE: BGP Advertising

    Posted 04-13-2021 12:15
    Edited by aaron.gould 04-13-2021 12:15
    looks like the *difference* is, ISP 1 and 2 get list...

    prefix-list external-supernets

    ...and ISP 3 gets list...

    prefix-list external-supernets-ISP-3

    (the parts not mentioned are common to all)

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



  • 3.  RE: BGP Advertising

    Posted 04-13-2021 13:25

    Hello,
    ISP 1 and ISP 2 get full networks. ISP 3 only should be getting partial networks, that is why external-supernets-ISP-3 only has the networks needed to be advertised to ISP-3.

    I am looking to see if the prefix-list  external-supernets-ISP-3 in policy-statement adv-supernets-ISP-3 will only advertise those networks to ISP-3

    Thank You




  • 4.  RE: BGP Advertising

    Posted 04-13-2021 15:17
    Edited by aaron.gould 04-13-2021 15:18
    the way i read your policy is....

    ISP 1, 2 and 3 all get list ---> "all-supernets"


    ISP 1 and 2 also get...


    prefix-list external-supernets {
    23.XXX.XX.0/24;
    137.XXX.XX6.0/24;
    137.XXX.XX7.0/24;
    192.XXX.X8.120/30;
    192.XXX.X10.0/24;
    198.XXX.XX3.0/24;
    198.XXX.XX1.0/24;
    198.XXX.XX4.0/24;
    208.XXX.46.0/24;
    208.XXX.47.0/24;


    ISP-3 also get...


    prefix-list external-supernets-ISP-3 {
    137.XXX.XX6.0/24;
    137.XXX.XX7.0/24;
    208.XXX.46.0/24;
    208.XXX.47.0/24;



    - Aaron






  • 5.  RE: BGP Advertising

    Posted 04-13-2021 17:38
    yes, your configuration looks good to have the advertised prefix list be different for isp 3 than the first two.  The routes can be either static or bgp but not aggregate.

    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP)
    http://puluka.com/home
    ------------------------------