Configuring IEEE 802.1Q Tunneling 23

When a double-tagged packet enters another trunk port in an intermediate or core switch in the service provider’s network, the outer tag is stripped for packet processing. When the packet exits another trunk port on the same core switch, the same SPVLAN tag is again added to the packet.

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.

Customer A (VLANs 1-10)

 

 

 

 

QinQ Tunneling

 

 

VLAN 10

Service Provider

Service Provider

 

 

(edge switch A)

(edge switch B)

Tunn

el

Access Port

 

 

 

 

 

 

 

 

 

Tunne

l A

ccess Port

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Tunnel Uplink Ports

 

 

 

 

 

 

 

VLAN 20

 

 

 

 

 

 

 

Double-Tagged Packets

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Customer B

Outer Tag - Service Provider VID

Inner Tag - Customer VID

(VLANs 1-50)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Customer A (VLANs 1-10)

VLAN 10

Tunnel Access Port

Tunnel Access Port VLAN 20

Customer B (VLANs 1-50)

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.

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Accton Technology 24/48-Port, ES4548D, ES4524D Layer 2 Flow for Packets Coming into a Tunnel Access Port, QinQ Tunneling