We need to extend a specific device directly connected to the core network to an existing L2VPN with an MPLS xconnect L2VPN.

But we encounter a problem. Indeed, one side recquire sub interface and VLAN tagging because we have many services (other L2VPN, IPv4 peering, IPv6 peering, ...) and the other side to put directly the interface into the VPN because the CPE cannot perform 802.1Q (vlan tagging).

We try to use "rewrite ingress tag push X symmetric" into the PE but it's not working.

How can we perform this ?

The device on the side with tagged interface is a Juniper MX and the device in the side with the untagged interface is a Cisco ASR.

Edit :

Added Configurations

Juniper Side (IP :

unit X {
    description "L2VPN";
    encapsulation vlan-ccc;
    vlan-id 42;
neighbor {
    interface INT.42 {
        virtual-circuit-id 42;
        encapsulation-type ethernet-vlan;

Cisco side (IP

interface INT.42 l2transport
encapsulation untagged
rewrite ingress tag push dot1q 42 symmetric

p2p to_2.2.2.2
 interface INT.42
 neighbor ipv4 pw-id 42
  pw-class L2VPN

pw-class L2VPN
encapsulation mpls
 transport-mode vlan
  • Please post your configuration from either side.
    – ditrapanij
    Nov 16, 2020 at 22:38
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer.
    – Ron Maupin
    Dec 31, 2020 at 4:01

1 Answer 1


On the Juniper side, you want to pop the 802.1Q tag on ingress and push upon egress. This way, the frame is untagged while traversing the MPLS core and when it reaches the Cisco. Below is how you configure it (doc link).

Note there are varying per-platform limitations of this configuration and not all Juniper boxes will necessarily support this.

unit X {
    # leave your existing config statements as-is, and add:
    input-vlan-map pop;
    output-vlan-map push;

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.