Cisco Catalyst 2950 Command Reference Manual page 525

Chapter 2 Catalyst 2950 and 2955 Cisco IOS Commands
The no switchport mode form resets the mode to dynamic desirable.
Trunk ports cannot coexist on the same switch.
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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Examples This example shows how to configure a port for access mode:
Switch(config-if)# switchport mode access
This example shows how set the interface to dynamic desirable mode:
Switch(config-if)# switchport mode dynamic desirable
This example shows how to configure a port for trunk mode:
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
switchport access
switchport trunk
0L-10102-01
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.
With GigaStack GBICs, dynamic trunking is only supported when two switches are connected by a
single GigaStack GBIC link. If trunking is required when more than two switches in a stack are
connected by GigaStack GBIC links, you must manually configure trunking in this manner:
– Manually shut down the GigaStack port by using the shutdown interface configuration
command.
Manually configure trunk mode on the GigaStack port by using the switchport mode trunk
–
interface configuration command on both GBIC interfaces to cause the interfaces to become
trunks.
Use the no shutdown interface configuration command to bring up the GigaStack port.
–
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 port.
Configures the trunk characteristics when an interface is in trunking mode.
Catalyst 2950 and Catalyst 2955 Switch Command Reference
switchport mode
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