Administrator Guide

Layer 2 Switching Commands 839
– except lists the VLANs that should be calculated by inverting the
defined list of VLANs. (VLANs are added except the ones specified.)
–
vlan-atom is either a single VLAN number from 1 to 4093 or a
continuous range of VLANs described by two VLAN numbers, the
lesser one first, separated by a hyphen.
•
valid–id —A valid VLAN id in the range 1–4093. This is the native VLAN
for the trunk port and will accept and send traffic on this VLAN in
untagged format.
Default Configuration
A trunk port is a member of all VLANs by default.
VLAN 1 is the default native VLAN on a trunk port. The default allowed
VLAN membership on a trunk port is all VLANs.
Command Mode
Interface Configuration (gigabitethernet, port-channel, tengigabitethernet,
fortygigabitethernet) mode
Interface Range mode
Port-Channel Range mode
User Guidelines
Untagged traffic received on a trunk port is forwarded on the native VLAN, if
configured.
To drop untagged traffic on a trunk port, remove the native VLAN from the
trunk port. (Ex. switchport trunk allowed vlan remove 1.) Management
traffic is still allowed on the trunk port in this configuration.
The no form of the command sets the allowed or native VLAN membership
back to the defaults.
It is possible to exclude VLANs that have not yet been created from trunk
port membership. For example, it is possible to exclude VLANs learned
dynamically via GVRP from being configured on a trunk port using this
command.
Example
console(config-if-Gi1/0/1)#switchport trunk allowed vlan 1-1024
2CSNXXX_SWUM204.book Page 839 Monday, January 25, 2016 1:25 PM