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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
78-17058-01
Chapter 13 Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Configuring IEEE 802.1Q Tunneling
IEEE 802.1Q Tunneling and Other Features
Although IEEE 802.1Q tunneling works well for Layer 2 packet switching, there are incompatibilities
between some Layer 2 features and Layer 3 switching.
Note Layer 3 switching is supported only when the metro IP access image is running on the switch.
• A tunnel port cannot be a routed port.
• IP routing is not supported on a VLAN that includes IEEE 802.1Q tunnel ports. Packets received
from a tunnel port are forwarded based only on Layer 2 information. If routing is enabled on a switch
virtual interface (SVI) that includes tunnel ports, untagged IP packets received from the tunnel port
are recognized and routed by the switch. Customers can access the internet through its native VLAN.
If this access is not needed, you should not configure SVIs on VLANs that include 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 is supported on tunnel ports.
• EtherChannel port groups are compatible with tunnel ports as long as the IEEE 802.1Q
configuration is consistent within an EtherChannel port group.
• UniDirectional Link Detection (UDLD) is supported on IEEE 802.1Q tunnel ports.
• Port Aggregation Protocol (PAgP) and Link Aggregation Control Protocol (LACP) are supported
only on IEEE 802.1Q tunnel ports that are network node interfaces (NNIs). UNIs do not support
PAgP and LACP.
• Loopback detection is supported on IEEE 802.1Q tunnel ports.
• When an NNI port is configured as an IEEE 802.1Q tunnel port, spanning-tree bridge protocol data
unit (BPDU) filtering is automatically enabled on the interface, and Cisco Discovery Protocol
(CDP) is automatically disabled on the interface. UNIs do not support BPDU filtering or CDP.
• In a UNI isolated VLAN, IEEE 802.1Q tunneled access ports are isolated from each other, but in a
UNI community VLAN, local switching occurs between these ports. For more information about
UNI VLANs, see Chapter 11, “Configuring VLANs.”
Configuring an IEEE 802.1Q Tunneling Port
Beginning in privileged EXEC mode, follow these steps to configure a port as an IEEE 802.1Q tunnel
port:
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode for 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 48).
Step 3
no shutdown Enable the port, if necessary. By default, UNIs are disabled, and NNIs are
enabled.