[j-nsp] A wierd problem with QinQ at QFX5100

[Andrew Osnach]

Hello,

I have a mixed VC (QFX5100 and 3500, if it means) with 14.1X53-D40.8. 
There's an interface that incapsulates C-VLANs into S-VLAN:

set interfaces ae31 flexible-vlan-tagging
set interfaces ae31 mtu 9216
set interfaces ae31 encapsulation extended-vlan-bridge
set interfaces ae31 unit 3174 vlan-id-list 21-22
set interfaces ae31 unit 3174 input-vlan-map push
set interfaces ae31 unit 3174 input-vlan-map vlan-id 3174
set interfaces ae31 unit 3174 output-vlan-map pop

The other side:

set interfaces ae0 flexible-vlan-tagging
set interfaces ae0 mtu 9216
set interfaces ae0 encapsulation extended-vlan-bridge
set interfaces ae0 unit 3174 vlan-id 3174

S-VLAN configured like this:
set vlans sv3174-qinq interface ae0.3174
set vlans sv3174-qinq interface ae31.3174

At this point everything works fine, but if I create a VLAN with the 
same ID as a C-VLAN (21 or 22):
set vlans v21-user vlan-id 21
the traffic in the C-VLAN 21 stops.
When I delete v21-user the traffic in C-VLAN 21 restores.

What's wrong with it and how can I fix it?

Kind regards.