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Catalyst 3750 Switch Command Reference
OL-8552-07
Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
switchport trunk
switchport trunk
Use the switchport trunk interface configuration command to set the trunk characteristics when the
interface is in trunking mode. Use the no form of this command to reset a trunking characteristic to the
default.
switchport trunk {allowed vlan vlan-list | encapsulation {dot1q | isl | negotiate} | native vlan
vlan-id | pruning vlan vlan-list}
no switchport trunk {allowed vlan | encapsulation | native vlan | {pruning vlan}
Syntax Description
The vlan-list format is all | none | [add | remove | except] vlan-atom [,vlan-atom...] where:
• all specifies all VLANs from 1 to 4094. This keyword is not allowed on commands that do not
permit all VLANs in the list to be set at the same time.
• none means an empty list. This keyword is not allowed on commands that require certain VLANs
to be set or at least one VLAN to be set.
• add adds the defined list of VLANs to those currently set instead of replacing the list. Valid IDs are
from 1 to 1005; extended-range VLANs (VLAN IDs greater than 1005) are valid in some cases.
Note You can add extended-range VLANs to the allowed VLAN list, but not to the
pruning-eligible VLAN list.
Separate nonconsecutive VLAN IDs with a comma; use a hyphen to designate a range of IDs.
• remove removes the defined list of VLANs from those currently set instead of replacing the list.
Valid IDs are from 1 to 1005; extended-range VLAN IDs are valid in some cases.
Note You can remove extended-range VLANs from the allowed VLAN list, but you cannot
remove them from the pruning-eligible list.
allowed vlan vlan-list Set the list of allowed VLANs that can receive and send traffic on this
interface in tagged format when in trunking mode. See the following vlan-list
format. The none keyword is not valid. The default is all.
encapsulation dot1q Set the encapsulation format on the trunk port to IEEE 802.1Q. With this
format, the switch supports simultaneous tagged and untagged traffic on a
port.
encapsulation isl Set the encapsulation format on the trunk port to Inter-Switch Link (ISL).
The switch encapsulates all received and sent packets with an ISL header and
filters native frames received from an ISL trunk port.
encapsulation
negotiate
Specify that if Dynamic Inter-Switch Link (DISL) and Dynamic Trunking
Protocol (DTP) negotiation do not resolve the encapsulation format, ISL is
the selected format.
native vlan vlan-id Set the native VLAN for sending and receiving untagged traffic when the
interface is in IEEE 802.1Q trunking mode. The range is 1 to 4094.
pruning vlan vlan-list Set the list of VLANs that are eligible for VTP pruning when in trunking
mode. The all keyword is not valid.
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