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CCNA Self-Study (ICND Exam): Extending Switched Networks with Virtual LANs

Chapter Description

Steve McQuerry discusses how VLANs operate to provide more effective networks by controlling broadcasts in your network.

VLAN Command Summary

Table 3-2 lists the commands covered in this chapter and briefly describes each command's function.

Table 3-2 VLAN Command Summary

Command

Description

vtp mode [server | client | transparent]

In global configuration mode, this command sets the operational VTP mode for the switch. The default is server.

vtp domain name

In global configuration mode, this command assigns a VTP domain name, which allows the switch to send VTP advertisements out trunk links. The default is NULL, which would allow a switch to join the first domain it received an update from.

show vtp status

Displays VTP status information including configuration revision number, domain name, and switch mode.

switchport mode [trunk | access | dynamic [desirable | auto | nonegotiate]]

In interface configuration mode, this configures the behavior of the interface. Trunk mode will force frame tagging. Dynamic mode can become a trunk if it negotiates with the other side of the link. Access mode is a nontrunk port.

switchport trunk encapsulation [isl | dot1q]

Used in interface configuration mode to specify a trunking protocol. For some switches, before you can set an interface to trunk mode, you must first specify the encapsulation.

show interface [type module/port] trunk

Displays trunking information about the active or specified trunk links on the switch.

show interface [type module/port] switchport

Displays Layer 2 configuration and operational parameters of the switch. This includes VLAN membership and trunking status.

vlan number

In global configuration mode, this command defines a VLAN and puts the switch into VLAN configuration mode. In VLAN configuration mode, commands such as name can be used to further define the VLAN.

show vlan [id vlan#]

Displays VLAN information. The id option allows you to specify a particular VLAN.

switchport access vlan [1-4096 | dynamic]

In interface configuration mode, this command assigns an access port to a VLAN or makes it a dynamic port.

show vlan brief

Displays a brief table of the VLANs, including the port membership for each VLAN.

show spanning-tree [vlan number]

Displays Spanning Tree information for the switch or a VLAN if the vlan option is used.


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