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Layer 2 Flow for Packets Coming into a Tunnel Access Port
A QinQ tunnel port may receive either tagged or untagged packets. No matter how many tags the incoming packet has, it is
treated as tagged packet.
The ingress process does source and destination lookups. If both lookups are successful, the ingress process writes the packet
to memory. Then the egress process transmits the packet. Packets entering a QinQ tunnel port are processed in the following
manner:
1.
New SPVLAN tags are added to all incoming packets, no matter how many tags they already have. The ingress process
constructs and inserts the outer tag (SPVLAN) into the packet based on the default VLAN ID and Tag Protocol Identifier
(TPID, that is, the ether-type of the tag). This outer tag is used for learning and switching packets. The priority of the inner
tag is copied to the outer tag if it is a tagged or priority tagged packet.
2.
After successful source and destination lookup, the ingress process sends the packet to the switching process with two
tags. If the incoming packet is untagged, the outer tag is an SPVLAN tag, and the inner tag is a dummy tag (8100 0000). If
the incoming packet is tagged, the outer tag is an SPVLAN tag, and the inner tag is a CVLAN tag.
3.
After packet classification through the switching process, the packet is written to memory with one tag (an outer tag) or
with two tags (both an outer tag and inner tag).
4.
The switch sends the packet to the proper egress port.
5.
If the egress port is an untagged member of the SPVLAN, the outer tag will be stripped. If it is a tagged member, the
outgoing packets will have two tags.
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User's Manual of IGSW-2840
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