[j-nsp] l2circuit between ASR9k and MX80

[Marcin Kurek]

Hello,

I'm doing some interoperability tests between Cisco and Juniper routers 
and I wanted to ask about a particular piece of config.
I would expect that it shouldn't work, but it works perfectly, so I'm a 
bit confused.

There is a l2vpn circuit between ASR9k and MX80 running in VLAN mode (VC 
Type 4).

------------------- ASR9k ------------------------------------

interface TenGigE0/0/1/5.3101 l2transport
  encapsulation dot1q 3101
  rewrite ingress tag pop 1 symmetric

l2vpn
!
  pw-class PW_TYPE_VLAN
   encapsulation mpls
    transport-mode vlan
   !
  !
!
  xconnect group XCONNECT_GROUP_2
   p2p PW2
    interface TenGigE0/0/1/5.3101
    neighbor ipv4 3.3.3.3 pw-id 101
     pw-class PW_TYPE_VLAN
    !
   !
  !
------------------- MX80 -------------------------------------

  ge-1/0/1 {
         description "ESXi 2 VMNIC3";
         flexible-vlan-tagging;
         encapsulation flexible-ethernet-services;
         unit 3101 {
             encapsulation vlan-ccc;
             vlan-id 3101;

protocols {
  l2circuit {
         neighbor 4.4.4.4 {
             interface ge-1/0/1.3101 {
                 virtual-circuit-id 101;
                 no-control-word;
                 encapsulation-type ethernet-vlan;
             }
         }
     }
}

In my understanding following things should happen:
- a frame coming to ASR9k from a CE is tagged with VLAN 3101
- we are doing VLAN tag manipulation on ASR9k, the tag is popped
- since we are using VC type 4, the PW forwarder adds a dummy tag 0 
before forwarding the frame
- MX80 should get the frame with tag 0 imposed

If above is true, how does the MX handle the dummy tag?


Thanks,
Marcin