Specifications

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Catalyst 2950 and Catalyst 2955 Switch Command Reference
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Chapter 2 Cisco IOS Commands
switchport trunk
• except lists the VLANs that should be calculated by inverting the defined list of VLANs. (VLANs
are added except the ones specified.) Valid IDs are from 2 to 1001. Separate nonconsecutive VLAN
IDs with a comma; do not enter a space after the comma. Use a hyphen to designate a range of IDs;
do not enter a space before or after the hyphen. Do not enter leading zeros.
• vlan-atom is either a single VLAN number from 1 to 4094 when the EI is installed and 1 to 1005
when the SI is installed, a list of nonconsecutive VLANs, or a continuous range of VLANs described
by two VLAN numbers, the lower one first, separated by a hyphen.
For a list of nonconsecutive VLAN IDs, separate the VLAN IDs with a comma. Do not enter a space
after the comma. Do not enter leading zeroes.
For a continuous range of VLAN IDs, use a hyphen to designate the range. Do not enter a space
before or after the hyphen. Do not enter leading zeroes.
These are examples showing how to specify one or more VLANs:
– Single VLAN—101
– List of nonconsecutive VLANs—10,12,14,16,18
– Continuous range of VLANs—10-15
– List of VLAN continuous ranges—10-15,20-24
– List of nonconsecutive VLANs and VLAN continuous ranges—8,11,20-24,44
Defaults VLAN 1 is the default native VLAN ID on the port.
The default for all VLAN lists is to include all VLANs.
Command Modes Interface configuration
Command History
Usage Guidelines A trunk port cannot be a secure port or a monitor port. However, a static-access port can monitor a
VLAN on a trunk port. The VLAN monitored is the one associated with the static-access port.
Allowed VLAN:
• The no form of the allowed vlan command resets the list to the default list, which allows all VLANs.
• You cannot remove VLAN 1 or VLANs 1002 to 1005 from the allowed VLAN list.
Native VLANs:
• All untagged traffic received on an 802.1Q trunk port is forwarded with the native VLAN
configured for the port.
• If a packet has a VLAN ID that is the same as the sending port native VLAN ID, the packet is sent
without a tag; otherwise, the switch sends the packet with a tag.
• The no form of the native vlan command resets the native mode VLAN to the appropriate default
VLAN for the device.
Release Modification
12.1(6)EA2 This command was first introduced.