The value of sysNewQinqUntaggedSap controls the forwarding of
packets on a QinQ X.0 access SAP.
When sysNewQinqUntaggedSap is set to true, the SAP will only accept:
- frames with a single tag matching the SAP's outer tag or,
- frames with double tag where the outer tag matches the SAP's outer
tag and inner tag is set to 0.
When sysNewQinqUntaggedSap is set to false, forwarding of packets
remains unchanged.