Configuring 802.1Q Tunneling; Default 802.1Q Tunneling Configuration; 802.1Q Tunneling Configuration Guidelines; Native Vlans - Cisco Catalyst 3750 Software Configuration Manual

Configuring 802.1Q Tunneling

The switch supports intelligent 802.1Q tunneling QoS, or the ability to copy the inner CoS value to the
outer CoS value. For more information, see the
Domain" section on page 26-42
page

Configuring 802.1Q Tunneling

This section includes this information about configuring 802.1Q tunneling:
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Default 802.1Q Tunneling Configuration

By default, 802.1Q tunneling is disabled because the default switchport mode is dynamic auto. Tagging
of 802.1Q native VLAN packets on all 802.1Q trunk ports is also disabled.

802.1Q Tunneling Configuration Guidelines

When you configure 802.1Q tunneling, you should always use an asymmetrical link between the
customer device and the edge switch, with the customer device port configured as an 802.1Q trunk port
and the edge switch port configured as a tunnel port.
Assign tunnel ports only to VLANs that are used for tunneling.
Configuration requirements for native VLANs and maximum transmission units (MTUs) are explained
in the next sections.

Native VLANs

When configuring 802.1Q tunneling on an edge switch, you must use 802.1Q trunk ports for sending out
packets into the service-provider network. However, packets going through the core of the
service-provider network might be carried through 802.1Q trunks, ISL trunks, or nontrunking links.
When 802.1Q trunks are used in these core switches, the native VLANs of the 802.1Q trunks must not
match any native VLAN of the nontrunking (tunneling) port on the same switch because traffic on the
native VLAN would not be tagged on the 802.1Q transmitting trunk port.
See
at the ingress edge switch in the service-provider network (Switch B). Switch A of Customer X sends a
tagged packet on VLAN 30 to the ingress tunnel port of Switch B in the service-provider network, which
belongs to access VLAN 40. Because the access VLAN of the tunnel port (VLAN 40) is the same as the
native VLAN of the edge switch trunk port (VLAN 40), the metro tag is not added to tagged packets
received from the tunnel port. The packet carries only the VLAN 30 tag through the service-provider
network to the trunk port of the egress edge switch (Switch C) and is misdirected through the egress
switch tunnel port to Customer Y.
Catalyst 3750 Metro Switch Software Configuration Guide
13-4
26-45.
Default 802.1Q Tunneling Configuration, page 13-4
802.1Q Tunneling Configuration Guidelines, page 13-4
802.1Q Tunneling and Other Features, page 13-6
Configuring an 802.1Q Tunneling Port, page 13-6
Figure 13-3. VLAN 40 is configured as the native VLAN for the 802.1Q trunk port from Customer X
Chapter 13 Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
"Configuring the Trust State on Ports Within the QoS
and the "Configuring the CoS Value for an Interface" section on
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