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iBGP inet6-vpn next-hop change

  • 1.  iBGP inet6-vpn next-hop change

    Posted 04-23-2021 10:35
    Hi, 

    i have maybe weird question.  I am running iBGP session (from exabgp software over ipv6) to VRF on Juniper MX router. Juniper acts as router-reflector in our AS. And I am trying inject routes into inet6-vpn on other routers over this RR. 

    iBGP session between exabgp and MX in routing-instance 
    ISP-priv-sychrov {
        protocols {
            bgp {
                path-selection always-compare-med;
                group EXABGP1 {
                    type internal;
                    local-address 2aFF:FFFF:2::1;
                    import SNET-ibgp-IN;
                    export SNET-ibgp-OUT;
                    peer-as 1234;
                    local-as 1234;
                    neighbor 2aFF:FFFF:FFFF:2::5 {
                        family inet6 {
                            unicast;
                        }
                    }
                }
            }
        }
        instance-type vrf;
        interface lo0.2;
        route-distinguisher 1234L:1100;
        vrf-target {
            import target:1234L:1100;
            export target:1234L:1100;
        }
        vrf-table-label;
    }
    ​
    received routes from iBGP session exabgp<-> routing-instance ISP-priv-sychrov :
    ISP-priv-sychrov.inet6.0: 12 destinations, 12 routes (12 active, 0 holddown, 0 hidden)
      Prefix                  Nexthop              MED     Lclpref    AS path
      2aFF:FFFF:1201:300::/56
    *                         2aFF:FFFF:1200::66           100        I
      2aFF:FFFF:1201:400::/56
    *                         2aFF:FFFF:1200::67           100        I
    ​

    Those nexthops are indirect routes to subnets on different PE routers in this L3VPN (we are solving DHCPv6 PD problem, but its not important). And i want it to be propagated to all PE routers in this L3VPN. 

    configuration of those PE routers MP BGP

    root@mx204> show configuration protocols bgp
    group ISP {
        type internal;
        local-address 1.2.3.4;
        import ISP-ibgp-IN;
        family inet {
            unicast;
        }
        family inet-vpn {
            unicast {
                loops 2;
            }
        }
        family inet6 {
            labeled-unicast {
                explicit-null;
            }
        }
        family inet6-vpn {
            unicast {
                loops 2;
            }
        }
        export SNET-ibgp-OUT;
        cluster 1.2.3.4;
        neighbor 123.189.152.255;
        
    }

    Propagation works, but it changes next-hop to Self.  But there is no policy that make it happen. And this is what i am not understanding why happens. 
    advertised routers for inet6-vpn session with PE router (RR enabled)

    root@mx204> show route table ISP-priv-sychrov.inet6.0 advertising-protocol bgp 123.189.152.255
    
    ISP-priv-sychrov.inet6.0: 12 destinations, 12 routes (12 active, 0 holddown, 0 hidden)
      Prefix                  Nexthop              MED     Lclpref    AS path
      2aFF:FFFF:1201:300::/56
    *                         Self                         100        I
      2aFF:FFFF:1201:400::/56
    *                         Self                         100        I
    

    extensive of this routes:

    * 2aFF:FFFF:1201:400::/56 (1 entry, 1 announced)
     BGP group ISP type Internal
         Route Distinguisher: 1234L:1100
         VPN Label: 201
         Nexthop: Self
         Flags: Nexthop Change
         Localpref: 100
         AS path: [1234] I
         Communities: target:1234L:1100
    
    


    Maybe this behavior is correct becouse this routes does not have lable information that is neccesary to make them works in inet6-vpn. But since this routes purpouse is to be injected into PE routers to direct towards clients CPE routers (PD) i need to propaget them withou changes. And final routing next-hop on all PEs (also this MX RR) should be find through indirect next-hop resolution (these subnets that next-hops lay in are of course in same RT, i mean this 2aFF:FFFF:1200::/64 subnet). 

    Is it possible to push this MX route-reflector to not change next-hops when advertising to his peers in inet6-vpn family? 
    Thanks a lot for your suggestions.

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    PETR DZIACK
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