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Configuring VLANs

Configuring VLANs

VLANs allow you to segment your network, limiting broadcast domains and organizing your network hierarchically.

To configure VLANs on the switch, perform these tasks:

Step 1 Configure VLAN Trunk Protocol---Create a VLAN Trunk Protocol (VTP) domain and set the VTP mode on the switch.

Step 2 Configure VLANs---Create VLANs in the VTP domain and assign switch ports to those VLANs.

Configure VLAN Trunk Protocol

VTP propagates information about the VLAN configuration throughout the switched network.

Note VTP only exchanges VLAN information over VLAN trunk links. For information on configuring trunk links, see the "Configuring EtherChannel and VLAN Trunks" section.

The switch can operate in any one of these three VTP modes:

Note Before you configure VLANs on the switch, you should decide whether to use VTP. If you decide to use VTP, you need to decide whether the switch should function as a VTP client or a VTP server. If you are connecting the switch to an existing network, make sure your VTP configuration reflects the strategy used in the rest of the network.

Configure the Switch as a VTP Server

When a switch is configured as a VTP server, you must define a VTP domain before you can create VLANs.

To configure a switch as a VTP server, perform this task in privileged mode:
Task Command

Step 1 Assign a name to the VTP management domain.

set vtp domain name

Step 2 Set the VTP mode.

set vtp mode server

Step 3 Verify the VTP configuration.

show vtp domain

This example shows how to configure a switch as a VTP server:

Console> (enable) set vtp domain BigCorp
VTP domain BigCorp modified
Console> (enable) set vtp mode server
VTP domain BigCorp modified
Console> (enable) show vtp domain
Domain Name                      Domain Index VTP Version Local Mode  Password
-------------------------------- ------------ ----------- ----------- ----------
BigCorp                          1            2           server      -
 
Vlan-count Max-vlan-storage Config Revision Notifications
---------- ---------------- --------------- -------------
5          1023             0               disabled
 
Last Updater    V2 Mode  Pruning  PruneEligible on Vlans
--------------- -------- -------- -------------------------
0.0.0.0         disabled disabled 2-1000
Console> (enable)

Configure the Switch as a VTP Client

When a switch is a VTP client, you cannot configure VLANs on the switch; instead, you configure VLANs on a VTP server in the same VTP domain as the client. The VTP client synchronizes its VLAN configuration to the configuration of the server.

To configure a switch as a VTP client, perform this task in privileged mode:
Task Command

Step 1 Assign a name to the VTP management domain.

set vtp domain name

Step 2 Set the VTP mode.

set vtp mode client

Step 3 Verify the VTP configuration. (It might take a few moments before a VTP client learns the VTP and VLAN configuration information from neighboring switches.)

show vtp domain

This example shows how to configure a switch as a VTP client:

Console> (enable) set vtp domain BigCorp
VTP domain BigCorp modified
Console> (enable) set vtp mode client   
VTP domain BigCorp modified
Console> (enable) show vtp domain
Domain Name                      Domain Index VTP Version Local Mode  Password
-------------------------------- ------------ ----------- ----------- ----------
BigCorp                          1            2           client      -
 
Vlan-count Max-vlan-storage Config Revision Notifications
---------- ---------------- --------------- -------------
5          1023             0               disabled
 
Last Updater    V2 Mode  Pruning  PruneEligible on Vlans
--------------- -------- -------- -------------------------
0.0.0.0         disabled disabled 2-1000
Console> (enable)

Configure the Switch as VTP Transparent

When a switch is in VTP transparent mode, you must configure VLAN information manually on the switch. A VTP-transparent switch does not advertise its VLAN configuration information to other switches and will ignore VTP updates from VTP clients and servers.

To configure a switch for VTP transparent mode, perform this task in privileged mode:
Task Command

Step 1 Set the VTP mode.

set vtp mode transparent

Step 2 Verify the VTP configuration.

show vtp domain

This example shows how to configure a switch as VTP transparent:

Console> (enable) set vtp mode transparent
VTP domain  modified
Console> (enable) show vtp domain
Domain Name                      Domain Index VTP Version Local Mode  Password
-------------------------------- ------------ ----------- ----------- ----------
                                 1            2           Transparent -
 
Vlan-count Max-vlan-storage Config Revision Notifications
---------- ---------------- --------------- -------------
5          1023             0               disabled
 
Last Updater    V2 Mode  Pruning  PruneEligible on Vlans
--------------- -------- -------- -------------------------
0.0.0.0         disabled disabled 2-1000
Console> (enable)

Configure VLANs

When the switch is properly configured for VTP, you can create, modify, and delete VLANs on the switch (unless you configured the switch as a VTP client). When you configure a VLAN on a VTP server, the configuration information is distributed to switches throughout the VTP domain.

VTP clients and servers in the same domain update their VLAN configuration based on the advertised configuration. VTP transparent switches do not act on VTP updates; you must manually make changes to the VLAN configuration on such switches.

Typically, in an IP network, each VLAN is associated with a single IP subnetwork. That is, all of the hosts in a given VLAN belong to a single subnet, use the same subnet mask, and use one or more default gateways connected to that subnetwork. Remember that stations in different VLANs cannot communicate with one another without a router configured to route between the different VLANs.

The supervisor engine software supports many VLAN types, including Ethernet, Fiber Distributed Data Interface (FDDI), ATM, and Token Ring. This section describes only how to configure Ethernet VLANs. For information about configuring other types of VLANs, refer to the Software Configuration Guide for your switch.

Create VLANs

To configure an Ethernet VLAN in a VTP domain, perform this task in privileged mode:
Task Command

Step 1 Create a VLAN by assigning it a VLAN number and, if desired, a VLAN name.

set vlan vlan_num [name name]

Step 2 Verify the VLAN configuration.

show vlan vlan_num

This example shows how to create a VLAN and verify the VLAN configuration:

Console> (enable) set vlan 10 name Corporate
Vlan 10 configuration successful
Console> (enable) show vlan 10
VLAN Name                             Status    IfIndex Mod/Ports, Vlans
---- -------------------------------- --------- ------- ------------------------
10   Corporate                        active    103     
 
 
VLAN Type  SAID       MTU   Parent RingNo BrdgNo Stp  BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ ------ ---- -------- ------ ------
10   enet  100010     1500  -      -      -      -    -        0      0
 
 
VLAN DynCreated
---- ----------
10   static    
 
 
VLAN AREHops STEHops Backup CRF 1q VLAN
---- ------- ------- ---------- -------
Console> (enable)

Assign Switch Ports to VLANs

After you create a VLAN, you can assign one or more switch ports to the VLAN. Devices connected to those ports will belong to that VLAN. Make sure the connected device is properly configured with an IP address, subnet mask, and default gateway in the subnet associated with the VLAN.

To add a switch port to a VLAN, perform this task in privileged mode:
Task Command

Step 1 Add one or more switch ports to a VLAN.

set vlan vlan_num mod_num/port_num

Step 2 Verify that the ports are properly assigned to the VLAN.

show vlan vlan_num

Step 3 Check to which VLAN a particular port belongs.

show port [mod_num/port_num]

This example shows how to assign ports to a VLAN and how to verify to which VLAN the ports belong:

Console> (enable) set vlan 10 3/1-2
VLAN 10 modified.
VLAN 1 modified.
VLAN  Mod/Ports
---- -----------------------
10    3/1-2
      
Console> (enable) show vlan 10
VLAN Name                             Status    IfIndex Mod/Ports, Vlans
---- -------------------------------- --------- ------- ------------------------
10   Corporate                        active    103     3/1-2
 
<... output truncated ...>
Console> (enable) show port 3
Port  Name               Status     Vlan       Level  Duplex Speed Type
----- ------------------ ---------- ---------- ------ ------ ----- ------------
 3/1                     connected  10         normal   full  1000 1000BaseSX
 3/2                     connected  10         normal   full  1000 1000BaseSX
<... output truncated ...>
Console> (enable)


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Posted: Fri Oct 1 13:02:17 PDT 1999
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