Switchport Trunk - Cisco Catalyst 3750 Command Reference Manual

switchport trunk

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Defaults The default encapsulation is negotiate.
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 Release
12.1(11)AX
12.1(14)EA1
Usage Guidelines Encapsulation:
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Native VLANs:
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Catalyst 3750 Switch Command Reference
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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 1 to 1005. Separate nonconsecutive VLAN
IDs with a comma; use a hyphen to designate a range of IDs.
vlan-atom is either a single VLAN number from 1 to 4094 or a continuous range of VLANs
described by two VLAN numbers, the lesser one first, separated by a hyphen.
Modification
This command was introduced.
The allowed vlan vlan-list add, remove, and except keywords were modified
to accept the VLAN1 and VLANs 1002 to 1005 values.
The switchport trunk encapsulation command is supported only for platforms and interface
hardware that can support both ISL and 802.1Q formats.
You cannot configure one end of the trunk as an 802.1Q trunk and the other end as an ISL or
nontrunk port. However, you can configure one port as an ISL trunk and a different port on the same
switch as an 802.1Q trunk.
If you enter the negotiate keywords and DTP negotiation does not resolve the encapsulation format,
ISL is the selected format. The no form of the command resets the trunk encapsulation format to the
default.
The no form of the encapsulation command resets the encapsulation format to the default.
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.
Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
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