802.1Q Tunneling And Other Features; Configuring An 802.1Q Tunneling Port - Cisco Catalyst 3750 Software Configuration Manual

Configuring 802.1Q Tunneling

802.1Q Tunneling and Other Features

Although 802.1Q tunneling works well for Layer 2 packet switching, there are incompatibilities with
some Layer 2 features and with Layer 3 switching.
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Configuring an 802.1Q Tunneling Port

Beginning in privileged EXEC mode, follow these steps to configure a port as an 802.1Q tunnel port:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
switchport access vlan vlan-id
Step 4
switchport mode dot1q-tunnel
Catalyst 3750 Metro Switch Software Configuration Guide
13-6
A tunnel port cannot be a routed port.
IP routing is not supported on a VLAN that includes 802.1Q ports. Packets received from a tunnel
port are forwarded based only on Layer 2 information. If routing is enabled on the switch virtual
interface (SVI) that includes tunnel ports, untagged IP packets received from the tunnel port are
recognized and routed by the switch. This allows the customer to access the Internet through its
native VLAN. If this access is not required, you should not configure SVIs on VLANs that include
tunnel ports.
Fallback bridging is not supported on tunnel ports. Because all 802.1Q-tagged packets received from
a tunnel port are treated as non-IP packets, if fallback bridging is enabled on VLANs that have
tunnel ports configured, IP packets would be improperly bridged across VLANs. Therefore, you
must not enable fallback bridging on VLANs with tunnel ports.
Tunnel ports do not support IP access control lists (ACLs).
Layer 3 quality of service (QoS) ACLs and other QoS features related to Layer 3 information are
not supported on tunnel ports. MAC-based QoS ACLs are supported on tunnel ports.
EtherChannel port groups are compatible with tunnel ports as long as the 802.1Q configuration is
consistent within an EtherChannel port group.
Port Aggregation Protocol (PAgP), Link Aggregation Control Protocol (LACP), and UniDirectional
Link Detection (UDLD) are supported on 802.1Q tunnel ports.
Dynamic Trunking Protocol (DTP) is not compatible with 802.1Q tunneling because you must
manually configure asymmetric links with tunnel ports and trunk ports.
VLAN Trunking Protocol (VTP) does not work between devices that are connected by an
asymmetrical link or devices that communicate through a tunnel.
Loopback detection is supported on 802.1Q tunnel ports.
When a port is configured as an 802.1Q tunnel port, spanning-tree bridge protocol data unit (BPDU)
filtering is automatically enabled on the interface. Cisco Discovery Protocol (CDP) is automatically
disabled on the interface.
Purpose
Enter global configuration mode.
Enter interface configuration mode and the interface to be configured as
a tunnel port. This should be the edge port in the service-provider network
that connects to the customer switch. Valid interfaces include physical
interfaces and port-channel logical interfaces (port channels 1 to 12).
Specify the default VLAN, which is used if the interface stops trunking.
This VLAN ID is specific to the particular customer.
Set the interface as an 802.1Q tunnel port.
Chapter 13 Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
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