MPLS xconnect L2VPN with tagged interface (subinterface) and untagged interface

Question

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 2.2.2.2) :

unit X {
    description "L2VPN";
    encapsulation vlan-ccc;
    vlan-id 42;
}
[...]
neighbor 1.1.1.1 {
    interface INT.42 {
        virtual-circuit-id 42;
        encapsulation-type ethernet-vlan;
    }

Cisco side (IP 1.1.1.1):

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

p2p to_2.2.2.2
 interface INT.42
 neighbor ipv4 2.2.2.2 pw-id 42
  pw-class L2VPN
 !
!

pw-class L2VPN
encapsulation mpls
 transport-mode vlan
!

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;
}