Configuring the ECN330-switch
2971553-KDU 137 365 Uen D 2006-06-16
When a packet enters the trunk port on the service provider’s egress switch, the
outer tag is again stripped for packet processing. However, the SPVLAN tag is
not added when it is sent out the tunnel port on the edge switch into the
customer’s network. The packet is sent as a normal IEEE 802.1Q-tagged frame,
preserving the original VLAN numbers used in the customer’s network.
Figure 118 QinQ Operational Concept
Layer 2 Flow for Packets Coming into a Tunnel 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
Double Tagged Packets
Outer Tag - Service Provider VID
Inner Tag - Customer VID
QinQ Tunneling
Service Provider
(edge router A)
Customer A
(VLANs 1-10)
Customer B
(VLANs 1-50)
Customer A
(VLANs 1-10)
Customer B
(VLANs 1-50)
Service Provider
(edge router B)
VLAN 10
Tunnel Port
Tunnel Port
VLAN 20
VLAN 10
Tunnel Port
Tunnel Port
VLAN 20
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