Routing

# show    
r1 {
    interfaces {
        em1 {
            unit 12 {
                vlan-id 12;
                family inet {
                    address 192.168.12.1/24;
                }
                family mpls;
            }
            unit 13 {
                vlan-id 13;
                family inet {
                    address 192.168.13.1/24;
                }
                family mpls;
            }
        }
        lo0 {
            unit 1 {
                family inet {
                    address 1.1.1.1/32;
                }
            }
        }
    }
    protocols {
        rsvp {
            interface em1.12;
            interface em1.13;
        }
        mpls {
            interface em1.12;
            interface em1.13;
        }
        ospf {
            traffic-engineering;
            area 0.0.0.0 {
                interface em1.12;
                interface em1.13;
                interface lo0.1 {
                    passive;
                }
            }
        }
    }
    routing-options {
        autonomous-system 100;
    }
}
r2 {
    interfaces {
        em2 {
            unit 12 {
                vlan-id 12;
                family inet {
                    address 192.168.12.2/24;
                }
                family mpls;
            }
            unit 27 {
                vlan-id 27;
                family inet {
                    address 192.168.27.2/24;
                }
            }
        }
        lo0 {
            unit 2 {
                family inet {
                    address 2.2.2.2/32;
                }
            }
        }
    }
    protocols {
        rsvp {
            interface em2.12;
        }
        mpls {
            label-switched-path r2-r3 {
                to 3.3.3.3;
            }
            interface em2.12;
        }
        bgp {
            group ibgp {
                type internal;
                local-address 2.2.2.2;
                neighbor 3.3.3.3 {
                    family inet-vpn {
                        unicast;
                    }
                }
            }
        }
        ospf {
            traffic-engineering;
            area 0.0.0.0 {
                interface em2.12;
                interface lo0.2 {
                    passive;
                }
            }
        }
    }
    policy-options {
        policy-statement vpn-a-export {
            term 1 {
                from protocol bgp;
                then {
                    community add vpn-a;
                    accept;
                }
            }
            term 2 {
                then reject;
            }
        }
        policy-statement vpn-a-import {
            term 1 {
                from {
                    protocol bgp;
                    community vpn-a;
                }
                then accept;
            }
            term 2 {
                then reject;
            }
        }
        community vpn-a members target:100:1;
    }
    routing-instances {
        vpn-a {
            instance-type vrf;
            interface em2.27;
            route-distinguisher 100:1;
            vrf-import vpn-a-import;
            vrf-export vpn-a-export;
            vrf-table-label;
            protocols {
                bgp {
                    group vpn-a {
                        type external;
                        neighbor 192.168.27.7 {
                            peer-as 78;
                            as-override;
                        }
                    }
                }
            }
        }
    }
    routing-options {
        autonomous-system 100;
    }
}
r3 {
    interfaces {
        em2 {
            unit 13 {
                vlan-id 13;
                family inet {
                    address 192.168.13.3/24;
                }
                family mpls;
            }
            unit 35 {
                vlan-id 35;
                family inet {
                    address 192.168.35.3/24;
                }
            }
        }
        lo0 {
            unit 3 {
                family inet {
                    address 3.3.3.3/32;
                }
            }
        }
    }
    protocols {
        rsvp {      
            interface em2.13;
        }
        mpls {
            label-switched-path r3-r2 {
                to 2.2.2.2;
            }
            interface em2.13;
        }
        bgp {
            group ibgp {
                type internal;
                local-address 3.3.3.3;
                neighbor 2.2.2.2 {
                    family inet-vpn {
                        unicast;
                    }
                }
            }
        }
        ospf {
            traffic-engineering;
            area 0.0.0.0 {
                interface em2.13;
                interface lo0.3 {
                    passive;
                }
            }
        }
    }
    routing-instances {
        vpn-a {
            instance-type vrf;
            interface em2.35;
            route-distinguisher 100:1;
            vrf-target target:100:1;
            vrf-table-label;
            protocols {
                bgp {
                    group ebgp {
                        type external;
                        neighbor 192.168.35.5 {
                            peer-as 200;
                        }
                    }
                }
            }       
        }
    }
    routing-options {
        autonomous-system 100;
    }
}
r4 {
    interfaces {
        em2 {
            unit 46 {
                vlan-id 46;
                family inet {
                    address 192.168.46.4/24;
                }
                family mpls;
            }
            unit 48 {
                vlan-id 48;
                family inet {
                    address 192.168.48.4/24;
                }
            }
        }
        lo0 {
            unit 4 {
                family inet {
                    address 4.4.4.4/32;
                }
            }
        }
    }
    protocols {
        rsvp {
            interface em2.46;
        }
        mpls {
            label-switched-path r4-r5 {
                to 5.5.5.5;
            }
            interface em2.46;
        }
        bgp {
            group ibgp {
                type internal;
                local-address 4.4.4.4;
                neighbor 5.5.5.5 {
                    family inet-vpn {
                        unicast;
                    }
                }
            }
        }
        ospf {
            traffic-engineering;
            area 0.0.0.0 {
                interface em2.46;
                interface lo0.4 {
                    passive;
                }
            }
        }
    }
    policy-options {
        policy-statement vpn-a-export {
            term 1 {
                from protocol bgp;
                then {
                    community add vpn-a;
                    accept;
                }
            }
            term 2 {
                then reject;
            }
        }
        policy-statement vpn-a-import {
            term 1 {
                from {
                    protocol bgp;
                    community vpn-a;
                }
                then accept;
            }
            term 2 {
                then reject;
            }
        }
        community vpn-a members target:100:1;
    }
    routing-instances {
        vpn-a {
            instance-type vrf;
            interface em2.48;
            route-distinguisher 100:1;
            vrf-import vpn-a-import;
            vrf-export vpn-a-export;
            vrf-table-label;
            protocols {
                bgp {
                    group vpn-a {
                        type external;
                        neighbor 192.168.48.8 {
                            peer-as 78;
                            as-override;
                        }
                    }
                }
            }
        }
    }
    routing-options {
        autonomous-system 200;
    }
}
r5 {
    interfaces {
        em1 {
            unit 35 {
                vlan-id 35;
                family inet {
                    address 192.168.35.5/24;
                }
            }
            unit 56 {
                vlan-id 56;
                family inet {
                    address 192.168.56.5/24;
                }
                family mpls;
            }
        }
        lo0 {
            unit 5 {
                family inet {
                    address 5.5.5.5/32;
                }
            }
        }           
    }
    protocols {
        rsvp {
            interface em1.56;
        }
        mpls {
            label-switched-path r5-r4 {
                to 4.4.4.4;
            }
            interface em1.56;
        }
        bgp {
            group ibgp {
                type internal;
                local-address 5.5.5.5;
                neighbor 4.4.4.4 {
                    family inet-vpn {
                        unicast;
                    }
                }
            }
        }
        ospf {
            traffic-engineering;
            area 0.0.0.0 {
                interface em1.56;
                interface lo0.5 {
                    passive;
                }
            }
        }
    }
    routing-instances {
        vpn-a {
            instance-type vrf;
            interface em1.35;
            route-distinguisher 100:1;
            vrf-target target:100:1;
            vrf-table-label;
            protocols {
                bgp {
                    group ebgp {
                        type external;
                        neighbor 192.168.35.3 {
                            peer-as 100;
                        }
                    }
                }
            }
        }
    }
    routing-options {
        autonomous-system 200;
    }
}
r6 {
    interfaces {
        em1 {
            unit 46 {
                vlan-id 46;
                family inet {
                    address 192.168.46.6/24;
                }
                family mpls;
            }
        }
        em2 {
            unit 56 {
                vlan-id 56;
                family inet {
                    address 192.168.56.6/24;
                }
                family mpls;
            }
        }
        lo0 {
            unit 6 {
                family inet {
                    address 6.6.6.6/32;
                }
            }
        }
    }
    protocols {
        rsvp {
            interface em1.46;
            interface em2.56;
        }
        mpls {
            interface em1.46;
            interface em2.56;
        }           
        ospf {
            traffic-engineering;
            area 0.0.0.0 {
                interface em1.46;
                interface em2.56;
                interface lo0.6 {
                    passive;
                }
            }
        }
    }
}
r7 {
    interfaces {
        em1 {
            unit 27 {
                vlan-id 27;
                family inet {
                    address 192.168.27.7/24;
                }
            }
        }
        lo0 {
            unit 7 {
                family inet {
                    address 7.7.7.7/32;
                }
            }
        }
    }
    protocols {
        bgp {
            group ebgp {
                type external;
                export direct;
                neighbor 192.168.27.2 {
                    peer-as 100;
                }
            }
        }
    }
    policy-options {
        policy-statement direct {
            term 1 {
                from protocol direct;
                then accept;
            }
        }
    }
    routing-options {
        autonomous-system 78;
    }
}
r8 {
    interfaces {
        em1 {
            unit 48 {
                vlan-id 48;
                family inet {
                    address 192.168.48.8/24;
                }
            }
        }
        lo0 {
            unit 8 {
                family inet {
                    address 8.8.8.8/32;
                }
            }
        }
    }
    protocols {
        bgp {
            group ebgp {
                type external;
                export direct;
                neighbor 192.168.48.4 {
                    peer-as 200;
                }
            }
        }
    }
    policy-options {
        policy-statement direct {
            term 1 {
                from protocol direct;
                then accept;
            }
        }
    }
    routing-options {
        autonomous-system 78;
    }
}

Hi,expert

I met an interesting question

let 's look into the route adverstised by r8 to r7

r8-r4-r5-r3-r2-r7

in r5 's route table

bgp.l3vpn.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)

100:1:8.8.8.8/32 (1 entry, 0 announced)
        *BGP    Preference: 170/-101
                Route Distinguisher: 100:1
                Next hop type: Indirect
                Next-hop reference count: 3
                Source: 4.4.4.4
                Next hop type: Router, Next hop index: 865
                Next hop: 192.168.56.6 via em1.56 weight 0x1, selected
                Label-switched-path r5-r4
                Label operation: Push 16, Push 299776(top)
                Protocol next hop: 4.4.4.4
                Push 16
                Indirect next hop: 8d630a8 131070
                State: <Active Int Ext>
                Local AS:   200 Peer AS:   200
                Age: 31:53      Metric2: 2
                Task: BGP_200.4.4.4.4+179
                AS path: 78 I
                Communities: target:100:1
                Import Accepted
                VPN Label: 16
                Localpref: 100
                Router ID: 4.4.4.4
                Secondary Tables: vpn-a.inet.0

vpn table

8.8.8.8/32 (1 entry, 1 announced)
        *BGP    Preference: 170/-101
                Route Distinguisher: 100:1
                Next hop type: Indirect
                Next-hop reference count: 3
                Source: 4.4.4.4
                Next hop type: Router, Next hop index: 865
                Next hop: 192.168.56.6 via em1.56 weight 0x1, selected
                Label-switched-path r5-r4
                Label operation: Push 16, Push 299776(top)
                Protocol next hop: 4.4.4.4
                Push 16
                Indirect next hop: 8d630a8 131070
                State: <Secondary Active Int Ext>
                Local AS:   200 Peer AS:   200
                Age: 31:53      Metric2: 2
                Task: BGP_200.4.4.4.4+179
                Announcement bits (2): 0-BGP RT Background 1-KRT
                AS path: 78 I
                Communities: target:100:1
                Import Accepted
                VPN Label: 16
                Localpref: 100
                Router ID: 4.4.4.4
                Primary Routing Table bgp.l3vpn.0

in r3 's route table

# run show route 8.8.8.8/32 logical-system r3 detail

vpn-a.inet.0: 4 destinations, 4 routes (4 active, 0 holddown, 0 hidden)
8.8.8.8/32 (1 entry, 1 announced)
        *BGP    Preference: 170/-101
                Next hop type: Router, Next hop index: 895
                Next-hop reference count: 2
                Source: 192.168.35.5
                Next hop: 192.168.35.5 via em2.35, selected
                State: <Active Ext>
                Peer AS:   200
                Age: 34:59
                Task: BGP_200.192.168.35.5+52468
                Announcement bits (2): 0-BGP RT Background 1-KRT
                AS path: 200 78 I
                Communities: target:100:1
                Accepted
                Localpref: 100
                Router ID: 192.168.35.5

here is the question,when r3 advertise this 8.8.8.8 to r2,whether it will add another target:100:1 because there is a config in vpn-a
:

routing-instances {
    vpn-a {
        instance-type vrf;
        interface em2.35;
        route-distinguisher 100:1;
        vrf-target target:100:1;

in r2 's route table:

# run show route 8.8.8.8/32 logical-system r2 detail   

vpn-a.inet.0: 5 destinations, 6 routes (5 active, 0 holddown, 0 hidden)
8.8.8.8/32 (1 entry, 1 announced)
        *BGP    Preference: 170/-101
                Route Distinguisher: 100:1
                Next hop type: Indirect
                Next-hop reference count: 6
                Source: 3.3.3.3
                Next hop type: Router, Next hop index: 893
                Next hop: 192.168.12.1 via em2.12 weight 0x1, selected
                Label-switched-path r2-r3
                Label operation: Push 16, Push 299808(top)
                Protocol next hop: 3.3.3.3
                Push 16
                Indirect next hop: 8d1f0a8 131073
                State: <Secondary Active Int Ext>
                Local AS:   100 Peer AS:   100
                Age: 37:15      Metric2: 2
                Task: BGP_100.3.3.3.3+179
                Announcement bits (2): 0-BGP RT Background 1-KRT
                AS path: 200 78 I
                Communities: target:100:1
                Import Accepted
                VPN Label: 16
                Localpref: 100
                Router ID: 3.3.3.3
                Primary Routing Table bgp.l3vpn.0

bgp.l3vpn.0: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden)

100:1:8.8.8.8/32 (1 entry, 0 announced)
        *BGP    Preference: 170/-101
                Route Distinguisher: 100:1
                Next hop type: Indirect
                Next-hop reference count: 6
                Source: 3.3.3.3
                Next hop type: Router, Next hop index: 893
                Next hop: 192.168.12.1 via em2.12 weight 0x1, selected
                Label-switched-path r2-r3
                Label operation: Push 16, Push 299808(top)
                Protocol next hop: 3.3.3.3
                Push 16
                Indirect next hop: 8d1f0a8 131073
                State: <Active Int Ext>
                Local AS:   100 Peer AS:   100
                Age: 37:15      Metric2: 2
                Task: BGP_100.3.3.3.3+179
                AS path: 200 78 I
                Communities: target:100:1
                Import Accepted
                VPN Label: 16
                Localpref: 100
                Router ID: 3.3.3.3
                Secondary Tables: vpn-a.inet.0
in r7:

# run show route 8.8.8.8/32 logical-system r7 detail   

inet.0: 5 destinations, 6 routes (5 active, 0 holddown, 1 hidden)
8.8.8.8/32 (1 entry, 1 announced)
        *BGP    Preference: 170/-101
                Next hop type: Router, Next hop index: 779
                Next-hop reference count: 4
                Source: 192.168.27.2
                Next hop: 192.168.27.2 via em1.27, selected
                State: <Active Ext>
                Local AS:    78 Peer AS:   100
                Age: 39:00
                Task: BGP_100.192.168.27.2+59993
                Announcement bits (1): 0-KRT
                AS path: 100 200 100 I
                Communities: target:100:1
                Accepted
                Localpref: 100
                Router ID: 192.168.27.2

1:why not r3 add another rt in this route?it seems rt community is always there,the whole path!

2: I can see rd is removed when pe import vpn route to its CE,right?

Hi Rob,

I believe RT being a "transistive extended community" you will see it as part of the route along the entire path after its addition.

I did a quick check on RFCs to find what has to be the behavior when route already has extended community. I couldn't find a conclusive answer.

RFC1997:
========
   A BGP speaker receiving a route that doesn't have the Extended
   Communities attribute MAY append this attribute to the route when
   propagating it to its peers.

   A BGP speaker receiving a route with the Extended Communities
   attribute MAY modify this attribute according to the local policy.


RFC436
======
Section 7

            d) Use of BGP makes it easy for the CE to pass attributes of
               the routes to the PE.  A complete specification of the
               set of attributes and their use is outside the scope of
               this document.  However, some examples of the way this
               may be used are the following:

Also I did a quick lab test and JUNOS don't add same extended community twice.
In one of my test, I have policy to add community twice, but eventually the route had only one community unless I had these community as different.

policy-statement expo {
    from {
        route-filter 200.1.0.0/24 exact;
    }
    then {
        community add rt-1;
        community add rt-2;
        accept;
    }
}
community rt-1 members target:100:100;
community rt-2 members target:100:100;

In another test, I had CE advertising the route with RT community, then PE doesn't add one more. It keeps as it.

So looks like when the VPN route consists of intended RT community, then JUNOS don't modify it.

Regards

Surya

haha,Surya

yes,it seems it is the behavior of junos