Switchport Mode - Cisco Catalyst 3750 Command Reference Manual

Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
To autonegotiate trunking, the interfaces must be in the same VTP domain. Trunk negotiation is managed
by the Dynamic Trunking Protocol (DTP), which is a point-to-point protocol. However, some
internetworking devices might forward DTP frames improperly, which could cause misconfigurations.
To avoid this, you should configure interfaces connected to devices that do not support DTP to not
forward DTP frames, which turns off DTP.
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Access port and trunk ports are mutually exclusive.
The 802.1x feature interacts with switchport modes in these ways:
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Examples
This example shows how to configure a port for access mode:
Switch(config)# interface gigabitethernet2/0/1
Switch(config-if)# switchport mode access
This example shows how set the port to dynamic desirable mode:
Switch(config)# interface gigabitethernet2/0/1
Switch(config-if)# switchport mode dynamic desirable
This example shows how to configure a port for trunk mode:
Switch(config)# interface gigabitethernet2/0/1
Switch(config-if)# switchport mode trunk
You can verify your settings by entering the show interfaces interface-id switchport privileged EXEC
command and examining information in the Administrative Mode and Operational Mode rows.
Related Commands Command
show interfaces
switchport access
switchport trunk
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If you do not intend to trunk across those links, use the switchport mode access interface
configuration command to disable trunking.
To enable trunking to a device that does not support DTP, use the switchport mode trunk and
switchport nonegotiate interface configuration commands to cause the interface to become a trunk
but to not generate DTP frames.
If you try to enable 802.1x on a trunk port, an error message appears, and 802.1x is not enabled. If
you try to change the mode of an 802.1x-enabled port to trunk, the port mode is not changed.
If you try to enable 802.1x on a port set to dynamic auto or dynamic desirable, an error message
appears, and 802.1x is not enabled. If you try to change the mode of an 802.1x-enabled port to
dynamic auto or dynamic desirable, the port mode is not changed.
If you try to enable 802.1x on a dynamic-access (VLAN Query Protocol [VQP]) port, an error
message appears, and 802.1x is not enabled. If you try to change an 802.1x-enabled port to dynamic
VLAN assignment, an error message appears, and the VLAN configuration is not changed.
switchport
Description
Displays the administrative and operational status of a switching
(nonrouting) port, including port blocking and port protection
settings.
Configures a port as a static-access or dynamic-access port.
Configures the trunk characteristics when an interface is in trunking
mode.
Catalyst 3750 Switch Command Reference

switchport mode

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