Interworking Protocol

Interworking is a protocol within Junos that allows layer 2 VPNs to be stitched together. Traditionally a loopback was performed within the tunnel services PIC to provided the stitching of the VPNs together. This is now handled within software via logical iw0 interface. This process removes some of the bandwidth constraints associated with the traditional approach.

The interworking between the two VPNs is carried out on an intermediary PE router. In order to configure this feature two logical iw0 interfaces must be configured with a peer unit statement under each unit to link the units together.

interface {
     iw0 {
          unit 100 {
               encapsulation vlan-ccc;
               vlan-id 100;
               peer unit 101;
          }
          unit 101
               encapsulation vlan-ccc;
               vlan-id 101;
               peer-unit 100;
          }
     }
}

The protocol must be enabled.

protocols {
     l2iw {
     }
}

The routing instances that require interworking must have the logical iw0 interfaces associate at the VRF level and the l2vpn site level. The routing-instance does not have any association with the interfaces that form part of the existing VPN as the feature is purely enable to interconnect two existing VPN sites from different routing instances.

routing-instances vpn-a {
     instance-type l2vpn;
     interface iw0.100;
     route-distinguisher 172.25.0.1:100;
     vrf-target target:65001:100;
     protocols {
          l2vpn {
               encapsulation-type ethernet-vlan;
               site CE-3 {
                    site-identifier 3;
                    interface iw0.100;
                         remote-site 1;
                    }
               }
          }
     }
}
routing-instances vpn-b {
     instance-type l2vpn;
     interface iw0.101;
     route-distinguisher 172.25.0.1:101;
     vrf-target target:65001:101;
     protocols {
          l2vpn {
               encapsulation-type ethernet-vlan;
               site CE-3 {
                    site-identifier 3;
                    interface iw0.101;
                         remote-site 2;
                    }
               }
          }
     }
}

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