Installation manual

3-192
SIGNAMAX LLC • www.signamax.eu
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 access 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.
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.
Tunnel Uplink Ports
Double-Tagged Packets
Outer Tag - Service Provider VID
Inner Tag - Customer VID
QinQ Tunneling
Service Provider
(edge switch A)
Customer A
(VLANs 1-10)
Customer B
(VLANs 1-50)
Customer A
(VLANs 1-10)
Customer B
(VLANs 1-50)
Service Provider
(edge switch B)
VLAN 10
Tunnel PortAccess
Tunnel Port
VLAN 20
Access
VLAN 10
Tunnel PortAccess
Tunnel Port
VLAN 20
Access