Cisco 6500 Series Software Configuration Manual page 182

Understanding How 802.1Q Tunneling Works
The customer switches are trunk connected, but with 802.1Q tunneling, the service provider switches
only use one service provider VLAN to carry all the customer VLANs, instead of directly carrying all
the customer VLANs.
With 802.1Q tunneling, tagged customer traffic comes from an 802.1Q trunk port on a customer device
and enters the service-provider edge switch through a tunnel port. The link between the 802.1Q trunk
port on a customer device and the tunnel port is called an asymmetrical link because one end is
configured as an 802.1Q trunk port and the other end is configured as a tunnel port. You assign the tunnel
port to an access VLAN ID unique to each customer. See
page 14-3.
Figure 14-1 IEEE 802.1Q Tunnel Ports in a Service-Provider Network
Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
14-2
Customer A
VLANs 1 to 100
Tunnel port
VLAN 30
Tunnel port
VLAN 30
Tunnel port
VLAN 40
Customer B
VLANs 1 to 200
Chapter 14 Configuring IEEE 802.1Q Tunneling and Layer 2 Protocol Tunneling
Figure 14-1 on page 14-2
Service
provider
Tunnel port
Trunk Trunk
ports ports
Tunnel port
Trunk
Asymmetric link
and Figure 14-2 on
Customer A
VLANs 1 to 100
VLAN 30
VLAN 40
Customer B
VLANs 1 to 200
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