Cisco Catalyst 3120 User Manual

16-7
Cisco Catalyst Blade Switch 3120 for HP Software Configuration Guide
OL-12247-01
Chapter 16 Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Understanding Layer 2 Protocol Tunneling
Use the no switchport mode dot1q-tunnel interface configuration command to return the port to the
default state of dynamic desirable. Use the no vlan dot1q tag native global configuration command to
disable tagging of native VLAN packets.
This example shows how to configure an interface as a tunnel port, enable tagging of native VLAN
packets, and verify the configuration. In this configuration, the VLAN ID for the customer connected to
Gigabit Ethernet interface 7 on stack member 1 is VLAN 22.
Switch(config)# interface gigabitethernet1/0/7
Switch(config-if)# switchport access vlan 22
% Access VLAN does not exist. Creating vlan 22
Switch(config-if)# switchport mode dot1q-tunnel
Switch(config-if)# exit
Switch(config)# vlan dot1q tag native
Switch(config)# end
Switch# show dot1q-tunnel interface gigabitethernet1/0/7
Port
-----
Gi1/0/1Port
-----
Switch# show vlan dot1q tag native
dot1q native vlan tagging is enabled
Understanding Layer 2 Protocol Tunneling
Customers at different sites connected across a service-provider network need to use various Layer 2
protocols to scale their topologies to include all remote sites, as well as the local sites. STP must run
properly, and every VLAN should build a proper spanning tree that includes the local site and all remote
sites across the service-provider network. Cisco Discovery Protocol (CDP) must discover neighboring
Cisco devices from local and remote sites. VLAN Trunking Protocol (VTP) must provide consistent
VLAN configuration throughout all sites in the customer network.
When protocol tunneling is enabled, edge switches on the inbound side of the service-provider network
encapsulate Layer 2 protocol packets with a special MAC address and send them across the
service-provider network. Core switches in the network do not process these packets but forward them
Step 5
exit Return to global configuration mode.
Step 6
vlan dot1q tag native (Optional) Set the switch to enable tagging of native VLAN packets on all
IEEE 802.1Q trunk ports. When not set, and a customer VLAN ID is the
same as the native VLAN, the trunk port does not apply a metro tag, and
packets could be sent to the wrong destination.
Step 7
end Return to privileged EXEC mode.
Step 8
show running-config
show dot1q-tunnel
Display the ports configured for IEEE 802.1Q tunneling.
Display the ports that are in tunnel mode.
Step 9
show vlan dot1q tag native Display IEEE 802.1Q native VLAN tagging status.
Step 10
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose

Cisco Catalyst 3120 Specifications

General

Brand	Cisco
Model	Catalyst 3120
Category	Switch
Language	English