Specifications
7-13
Cisco MWR 2941 Mobile Wireless Edge Router Release 3.5 Software Configuration Guide, Cisco IOS Release 15.1(3)MR
OL-26895-01
Chapter 7 Configuring VLANs
Configuring VLAN Trunks
is maintained by Cisco switches separated by a cloud of non-Cisco IEEE 802.1Q switches. The
non-Cisco IEEE 802.1Q cloud separating the Cisco switches is treated as a single trunk link between
the switches.
• If the native VLAN on one end of the trunk is different from the native VLAN on the other end,
spanning-tree loops might result. Make sure that the native VLAN for an IEEE 802.1Q trunk is the
same on both ends of the trunk link.
• Disabling spanning tree on the native VLAN of an IEEE 802.1Q trunk without disabling spanning
tree on every VLAN in the network can potentially cause spanning-tree loops. Leave spanning tree
enabled on the native VLAN of an IEEE 802.1Q trunk or disable spanning tree on every VLAN in
the network. Make sure that your network is loop-free before disabling spanning tree.
Default Layer 2 Ethernet Interface VLAN Configuration
Table 7-5 shows the default Layer 2 Ethernet interface VLAN configuration.
Configuring an Ethernet Interface as a Trunk Port
• Interaction with Other Features, page 7-13
• Defining the Allowed VLANs on a Trunk, page 7-14
• Configuring the Native VLAN for Untagged Traffic, page 7-15
Interaction with Other Features
Trunking interacts with other features in these ways:
• A trunk port cannot be a secure port.
• A trunk port cannot be a tunnel port.
• If you try to enable IEEE 802.1x on a trunk port, an error message appears, and IEEE 802.1x is not
enabled. If you try to change the mode of an IEEE 802.1x-enabled port to trunk, the port mode is
not changed.
Configuring a Trunk Port
Beginning in privileged EXEC mode, follow these steps to configure a port as an IEEE 802.1Q
trunk port:
Table 7-5 Default Layer 2 Ethernet Interface VLAN Configuration
Feature Default Setting
Interface mode switchport mode access
Allowed VLAN range VLANs 1–4094
Default VLAN (for access ports) VLAN 1
Native VLAN (for IEEE 802.1Q trunks) VLAN 1