•Ensurethat the native VLAN ID on the edge-switch trunk port is not within the customer VLAN range.
Forexample, if the trunk port carries traffic of VLANs 100 to 200, assign the native VLAN a number
outsidethat range.
Figure 11: Potential Problems with IEEE 802.1Q Tunneling and Native VLANs
System MTU
Thedefault system MTU for traffic on the switch is 1500 bytes. You can configure Fast Ethernet ports on the
switchmembers in the mixed hardware switchstack to support frameslarger than 1500 bytes by using the
systemmtu global configurationcommand.
Youcan configure 10-Gigabit and Gigabit Ethernet ports to support frames larger than 1500 bytes by using
thesystem mtu jumbo globalconfiguration command.
Thesystem MTU and system jumbo MTU values do not include the IEEE 802.1Q header. Because the IEEE
802.1Qtunneling feature increases the frame size by 4 bytes when the metro tag is added, you must configure
allswitches in the service-provider network to be able to process maximum frames by adding 4 bytes to the
systemMTU and systemjumbo MTU sizes.
Forexample, the switch supports amaximum frame size of 1496 bytes with one of these configurations:
•Theswitch has a system jumbo MTU value of 1500 bytes, and the switchport mode dot1q tunnel
interfaceconfiguration command is configuredon a10-Gigabit orGigabit Ethernet switchport.
•Theswitch member has a system MTU value of 1500 bytes, and the switchport mode dot1q tunnel
interfaceconfiguration command is configuredon aFast Ethernetport of the member.
Catalyst 2960-XR Switch VLAN Configuration Guide, Cisco IOS Release 15.0(2)EX1
128 OL-29440-01
Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
IEEE 802.1Q Tunneling Configuration Guidelines