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Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 17 Configuring IEEE 802.1Q Tunneling
Understanding How 802.1Q Tunneling Works
The customer routers are trunk connected, but with 802.1Q tunneling, the service provider routers 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 router 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
Figure 17-1 on page 17-2
and
Figure 17-2 on
page 17-3
.
Figure 17-1 IEEE 802.1Q Tunnel Ports in a Service-Provider Network
Customer A
VLANs 1 to 100
Customer B
VLANs 1 to 200
Customer B
VLANs 1 to 200
Customer A
VLANs 1 to 100
Tunnel port
VLAN 40
Tunnel port
VLAN 30
Trunk
ports
Trunk
ports
Tunnel port
VLAN 30
Tunnel port
VLAN 40
Service
provider
802.1Q trunk port
802.1Q trunk port
802.1Q trunk port
802.1Q trunk port
802.1Q trunk port
74016
Trunk
Asymmetric link
Tunnel port
VLAN 30
802.1Q trunk port
802.1Q trunk port
802.1Q trunk port
802.1Q trunk port