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The following are prerequisites and considerations for configuring VLANs:
The following are the restrictions for configuring VLANs:
Information About VLANs
A VLAN is a switched network that is logically segmented by function, project team, or application, without regard to the physical locations of the users. VLANs have the same attributes as physical LANs, but you can group end stations even if they are not physically located on the same LAN segment. Any switch port can belong to a VLAN, and unicast, broadcast, and multicast packets are forwarded and flooded only to end stations in the VLAN. Each VLAN is considered a logical network, and packets destined for stations that do not belong to the VLAN must be forwarded through a router or a switch supporting fallback bridging. In a switch stack, VLANs can be formed with ports across the stack. Because a VLAN is considered a separate logical network, it contains its own bridge Management Information Base (MIB) information and can support its own implementation of spanning tree.
VLANs are often associated with IP subnetworks. For example, all the end stations in a particular IP subnet belong to the same VLAN. Interface VLAN membership on the switch is assigned manually on an interface-by-interface basis. When you assign switch interfaces to VLANs by using this method, it is known as interface-based, or static, VLAN membership.
Traffic between VLANs must be routed or fallback bridged.
The switch can route traffic between VLANs by using switch virtual interfaces (SVIs). An SVI must be explicitly configured and assigned an IP address to route traffic between VLANs.
The switch supports VLANs in VTP client, server, and transparent modes. VLANs are identified by a number from 1 to 4094. VLAN IDs 1002 through 1005 are reserved for Token Ring and FDDI VLANs. VTP version 1 and version 2 support only normal-range VLANs (VLAN IDs 1 to 1005). In these versions, the switch must be in VTP transparent mode when you create VLAN IDs from 1006 to 4094. VTP version 3 supports the entire VLAN range (VLANs 1 to 4094). Extended range VLANs (VLANs 1006 to 4094) are supported only in VTP version 3. You cannot convert from VTP version 3 to VTP version 2 if extended VLANs are configured in the domain.
The switch or switch stack supports a total of 1005 (normal range and extended range) VLANs. However, the number of routed ports, SVIs, and other configured features affects the use of the switch hardware.
The switch supports per-VLAN spanning-tree plus (PVST+) or rapid PVST+ with a maximum of 128 spanning-tree instances. One spanning-tree instance is allowed per VLAN.
The switch supports IEEE 802.1Q trunking methods for sending VLAN traffic over Ethernet ports.
You configure a port to belong to a VLAN by assigning a membership mode that specifies the kind of traffic the port carries and the number of VLANs to which it can belong.
When a port belongs to a VLAN, the switch learns and manages the addresses associated with the port on a per-VLAN basis.
Membership Mode |
VLAN Membership Characteristics |
VTP Characteristics |
---|---|---|
Static-access |
A static-access port can belong to one VLAN and is manually assigned to that VLAN. |
VTP is not required. If you do not want VTP to globally propagate information, set the VTP mode to transparent. To participate in VTP, there must be at least one trunk port on the switch or the switch stack connected to a trunk port of a second switch or switch stack. |
Trunk (IEEE 802.1Q) : |
A trunk port is a member of all VLANs by default, including extended-range VLANs, but membership can be limited by configuring the allowed-VLAN list. You can also modify the pruning-eligible list to block flooded traffic to VLANs on trunk ports that are included in the list. |
VTP is recommended but not required. VTP maintains VLAN configuration consistency by managing the addition, deletion, and renaming of VLANs on a network-wide basis. VTP exchanges VLAN configuration messages with other switches over trunk links. |
Dynamic access |
A dynamic-access port can belong to one VLAN (VLAN ID 1 to 4094) and is dynamically assigned by a VLAN Member Policy Server (VMPS). The VMPS can be a Catalyst 6500 series switch, for example, but never a Catalyst 2960, 2960-S, or 2960-C switch. The Catalyst 2960, 2960-S, or 2960-C switch is a VMPS client. You can have dynamic-access ports and trunk ports on the same switch, but you must connect the dynamic-access port to an end station or hub and not to another switch. |
VTP is required. Configure the VMPS and the client with the same VTP domain name. To participate in VTP, at least one trunk port on the switch or a switch stack must be connected to a trunk port of a second switch or switch stack. |
Voice VLAN |
A voice VLAN port is an access port attached to a Cisco IP Phone, configured to use one VLAN for voice traffic and another VLAN for data traffic from a device attached to the phone. |
VTP is not required; it has no effect on a voice VLAN. |
Normal-range VLANs are VLANs with VLAN IDs 1 to 1005. If the switch is in VTP server or VTP transparent mode, you can add, modify or remove configurations for VLANs 2 to 1001 in the VLAN database. (VLAN IDs 1 and 1002 to 1005 are automatically created and cannot be removed.)
In VTP versions 1 and 2, the switch must be in VTP transparent mode when you create extended-range VLANs (VLANs with IDs from 1006 to 4094), but these VLANs are not saved in the VLAN database. VTP version 3 supports extended-range VLANs in VTP server and transparent mode.
Configurations for VLAN IDs 1 to 1005 are written to the file vlan.dat (VLAN database), and you can display them by entering the show vlan privileged EXEC command. The vlan.dat file is stored in flash memory. On a switch, the vlan.dat file is stored in flash memory on the stack master. Stack members have a vlan.dat file that is consistent with the stack master.
Although the switch does not support Token Ring connections, a remote device such as a Catalyst 5000 series switch with Token Ring connections could be managed from one of the supported switches. Switches running VTP Version 2 advertise information about these Token Ring VLANs:
Note |
For more information on configuring Token Ring VLANs, see the Catalyst 5000 Series Software Configuration Guide. |
You configure VLANs in the vlan global configuration command by entering a VLAN ID. Enter a new VLAN ID to create a VLAN, or enter an existing VLAN ID to modify that VLAN. You can use the default VLAN configuration or enter multiple commands to configure the VLAN. For more information about commands available in this mode, see the vlan global configuration command description in the command reference for this release. When you have finished the configuration, you must exit VLAN configuration mode for the configuration to take effect. To display the VLAN configuration, enter the show vlan privileged EXEC command.
The configurations of VLAN IDs 1 to 1005 are always saved in the VLAN database (vlan.dat file). If the VTP mode is transparent, they are also saved in the switch running configuration file. You can enter the copy running-config startup-config privileged EXEC command to save the configuration in the startup configuration file. In a switch stack, the whole stack uses the same vlan.dat file and running configuration. To display the VLAN configuration, enter the show vlan privileged EXEC command.
When you save VLAN and VTP information (including extended-range VLAN configuration information) in the startup configuration file and reboot the switch, the switch configuration is selected as follows:
Normal-range VLANs are VLANs with IDs from 1 to 1005. VTP 1 and 2 only support normal-range VLANs.
Follow these guidelines when creating and modifying normal-range VLANs in your network:
VTP 3 only supports extended-range VLANs. Extended-range VLANs are VLANs with IDs from 1006 to 4094.
Follow these guidelines when creating extended-range VLANs:
The following table displays the default configuration for Ethernet VLANs.
Note |
The switch supports Ethernet interfaces exclusively. Because FDDI and Token Ring VLANs are not locally supported, you only configure FDDI and Token Ring media-specific characteristics for VTP global advertisements to other switches. |
Parameter |
Default |
Range |
||
---|---|---|---|---|
VLAN ID |
1 |
1 to 4094.
|
||
VLAN name |
VLANxxxx, where xxxx represents four numeric digits (including leading zeros) equal to the VLAN ID number |
No range |
||
IEEE 802.10 SAID |
100001 (100000 plus the VLAN ID) |
1 to 4294967294 |
||
MTU Size |
1500 |
576-18190 |
||
Translational bridge 1 |
0 |
0 to 1005 |
||
Translational bridge 2 |
0 |
0 to 1005 |
||
VLAN state |
active |
active, suspend |
||
Remote SPAN |
disabled |
enabled, disabled |
||
Private VLANs |
none configured |
2 to 1001, 1006 to 4094 |
You can change only the MTU size, private VLAN, and the remote SPAN configuration state on extended-range VLANs; all other characteristics must remain at the default state.
How to Configure VLANs
You can set these parameters when you create a new normal-range VLAN or modify an existing VLAN in the VLAN database:
You can cause inconsistency in the VLAN database if you attempt to manually delete the vlan.dat file. If you want to modify the VLAN configuration, follow the procedures in this section.
Each Ethernet VLAN in the VLAN database has a unique, 4-digit ID that can be a number from 1 to 1001. VLAN IDs 1002 to 1005 are reserved for Token Ring and FDDI VLANs. To create a normal-range VLAN to be added to the VLAN database, assign a number and name to the VLAN.
Note |
With VTP version 1 and 2, if the switch is in VTP transparent mode, you can assign VLAN IDs greater than 1006, but they are not added to the VLAN database. |
2. vlan vlan-id
3. name vlan-name
4. mtu mtu-size
5. remote-span
7. show vlan {name vlan-name | id vlan-id}
When you delete a VLAN from a switch that is in VTP server mode, the VLAN is removed from the VLAN database for all switches in the VTP domain. When you delete a VLAN from a switch that is in VTP transparent mode, the VLAN is deleted only on that specific switch or a switch stack.
You cannot delete the default VLANs for the different media types: Ethernet VLAN 1 and FDDI or Token Ring VLANs 1002 to 1005.
Caution |
When you delete a VLAN, any ports assigned to that VLAN become inactive. They remain associated with the VLAN (and thus inactive) until you assign them to a new VLAN. |
Command or Action | Purpose | |
---|---|---|
Step 1 |
configure terminal Example: Switch# configure terminal |
|
Step 2 | no vlan vlan-id Example:
Switch(config)# no vlan 4
|
Removes the VLAN by entering the VLAN ID. |
Step 3 |
end Example: Switch(config)# end |
|
Step 4 | show vlan brief Example:
Switch# show vlan brief
|
Verifies the VLAN removal. |
You can assign a static-access port to a VLAN without having VTP globally propagate VLAN configuration information by disabling VTP (VTP transparent mode).
If you are assigning a port on a cluster member switch to a VLAN, first use the rcommand privileged EXEC command to log in to the cluster member switch.
If you assign an interface to a VLAN that does not exist, the new VLAN is created.
2. interface interface-id
3. switchport mode access
4. switchport access vlan vlan-id
6. show running-config interface interface-id
7. show interfaces interface-id switchport
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 |
configure terminal Example: Switch# configure terminal |
|||
Step 2 | interface interface-id Example:
Switch(config)# interface gigabitethernet2/0/1
|
Enters the interface to be added to the VLAN. |
||
Step 3 | switchport mode access Example:
Switch(config-if)# switchport mode access
|
Defines the VLAN membership mode for the port (Layer 2 access port). |
||
Step 4 | switchport access vlan vlan-id Example:
Switch(config-if)# switchport access vlan 2
|
Assigns the port to a VLAN. Valid VLAN IDs are 1 to 4094.
|
||
Step 5 |
end Example: Switch(config)# end |
|||
Step 6 | show running-config interface interface-id Example:
Switch# copy running-config startup-config
|
Verifies the VLAN membership mode of the interface. |
||
Step 7 | show interfaces interface-id switchport Example:
Switch# show interfaces gigabitethernet2/0/1
|
Verifies your entries in the Administrative Mode and the Access Mode VLAN fields of the display. |
With VTP version 1 and version 2, when the switch is in VTP transparent mode (VTP disabled), you can create extended-range VLANs (in the range 1006 to 4094). VTP 3 version supports extended-range VLANs in server or transparent move.
Extended-range VLANs enable service providers to extend their infrastructure to a greater number of customers. The extended-range VLAN IDs are allowed for any switchport commands that allow VLAN IDs.
With VTP version 1 or 2, extended-range VLAN configurations are not stored in the VLAN database, but because VTP mode is transparent, they are stored in the switch running configuration file, and you can save the configuration in the startup configuration file. Extended-range VLANs created in VTP version 3 are stored in the VLAN database.
You can change only the MTU size, private VLAN, and the remote SPAN configuration state on extended-range VLANs; all other characteristics must remain at the default state.
You create an extended-range VLAN in global configuration mode by entering the vlan global configuration command with a VLAN ID from 1006 to 4094. The extended-range VLAN has the default Ethernet VLAN characteristics and the MTU size, and RSPAN configuration are the only parameters you can change. See the description of the vlan global configuration command in the command reference for the default settings of all parameters. In VTP version 1 or 2, if you enter an extended-range VLAN ID when the switch is not in VTP transparent mode, an error message is generated when you exit VLAN configuration mode, and the extended-range VLAN is not created.
In VTP version 1 and 2, extended-range VLANs are not saved in the VLAN database; they are saved in the switch running configuration file. You can save the extended-range VLAN configuration in the switch startup configuration file by using the copy running-config startup-config privileged EXEC command. VTP version 3 saves extended-range VLANs in the VLAN database.
Note |
Before you create an extended-range VLAN, you can verify that the VLAN ID is not used internally by entering the show vlan internal usage privileged EXEC command. If the VLAN ID is used internally and you want to free it up, go to the Creating an Extended-Range VLAN with an Internal VLAN ID before creating the extended-range VLAN. |
2. vtp mode transparent
3. vlan vlan-id
4. mtu mtu size
5. remote-span
7. show vlan id vlan-id
8. copy running-config startup config
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 |
configure terminal Example: Switch# configure terminal |
|||
Step 2 | vtp mode transparent Example:
Switch(config)# vtp mode transparent
|
Configures the switch for VTP transparent mode, disabling VTP.
|
||
Step 3 | vlan vlan-id Example: Switch(config)# vlan 2000 Switch(config-vlan)# |
Enters an extended-range VLAN ID and enters VLAN configuration mode. The range is 1006 to 4094.
|
||
Step 4 | mtu mtu size Example: Switch(config-vlan)# mtu 1024
|
Modifies the VLAN by changing the MTU size. |
||
Step 5 | remote-span Example:
Switch(config-vlan)# remote-span
|
(Optional) Configures the VLAN as the RSPAN VLAN. |
||
Step 6 |
end Example: Switch(config)# end |
|||
Step 7 | show vlan id vlan-id Example:
Switch# show vlan id 2000
|
Verifies that the VLAN has been created. |
||
Step 8 | copy running-config startup config Example:
Switch# copy running-config startup-config
|
Saves your entries in the switch startup configuration file. To save an extended-range VLAN configuration, you need to save the VTP transparent mode configuration and the extended-range VLAN configuration in the switch startup configuration file. Otherwise, if the switch resets, it will default to VTP server mode, and the extended-range VLAN IDs will not be saved.
|
If you enter an extended-range VLAN ID that is already assigned to an internal VLAN, an error message is generated, and the extended-range VLAN is rejected. To manually free an internal VLAN ID, you must temporarily shut down the routed port that is using the internal VLAN ID.
1. show vlan internal usage
2. configure terminal
3. interface interface-id
4. shutdown
5. exit
6. vtp mode transparent
7. vlan vlan-id
8. exit
9. interface interface-id
10. no shutdown
11. end
12. copy running-config startup config
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 | show vlan internal usage Example:
Switch# show vlan internal usage
|
Displays the VLAN IDs being used internally by the switch. If the VLAN ID that you want to use is an internal VLAN, the display shows the routed port that is using the VLAN ID. Enter that port number in Step 3. |
||
Step 2 | configure terminal Example:
Switch# configure terminal
|
Enters global configuration mode. |
||
Step 3 | interface interface-id Example:
Switch(config)# interface gigabitethernet1/0/3
|
Specifies the interface ID for the routed port that is using the VLAN ID, and enters interface configuration mode. |
||
Step 4 | shutdown Example:
Switch(config-if)# shutdown
|
Shuts down the port to free the internal VLAN ID. |
||
Step 5 | exit Example:
Switch(config-if)# exit
|
Returns to global configuration mode. |
||
Step 6 | vtp mode transparent Example:
Switch(config)# vtp mode transparent
|
Sets the VTP mode to transparent for creating extended-range VLANs.
|
||
Step 7 | vlan vlan-id Example:
Switch(config-vlan)# vlan 2000
|
Enters the new extended-range VLAN ID, and enters VLAN configuration mode. |
||
Step 8 | exit Example:
Switch(config-vlan)# exit
|
Exits from VLAN configuration mode, and returns to global configuration mode. |
||
Step 9 | interface interface-id Example:
Switch(config)# interface gigabitethernet1/0/3
|
Specifies the interface ID for the routed port that you shut down in Step 4, and enters interface configuration mode. |
||
Step 10 | no shutdown Example:
Switch(config)# no shutdown
|
Reenables the routed port. It will be assigned a new internal VLAN ID. |
||
Step 11 | end Example:
Switch(config)# end
|
Returns to privileged EXEC mode. |
||
Step 12 | copy running-config startup config Example:
Switch# copy running-config startup-config
|
Saves your entries in the switch startup configuration file. To save an extended-range VLAN configuration, you need to save the VTP transparent mode configuration and the extended-range VLAN configuration in the switch startup configuration file. Otherwise, if the switch resets, it will default to VTP server mode, and the extended-range VLAN IDs will not be saved.
|
Command |
Purpose |
---|---|
show interfaces [vlan vlan-id] |
Displays characteristics for all interfaces or for the specified VLAN configured on the switch. |
Configuration Examples
This example shows how to create Ethernet VLAN 20, name it test20, and add it to the VLAN database:
Switch# configure terminal Switch(config)# vlan 20 Switch(config-vlan)# name test20 Switch(config-vlan)# end
This example shows how to configure a port as an access port in VLAN 2:
Switch# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Switch(config)# interface gigabitethernet2/0/1 Switch(config-if)# switchport mode access Switch(config-if)# switchport access vlan 2 Switch(config-if)# end
This example shows how to create a new extended-range VLAN with all default characteristics, enter VLAN configuration mode, and save the new VLAN in the switch startup configuration file:
Switch(config)# vtp mode transparent Switch(config)# vlan 2000 Switch(config-vlan)# end Switch# copy running-config startup config
After configuring VLANs, you can configure the following:
Related Topic | Document Title |
---|---|
For complete syntax and usage information for the commands used in this chapter. |
Standard/RFC | Title |
---|---|
— |
— |
MIB | MIBs Link |
---|---|
All supported MIBs for this release. |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
Description | Link |
---|---|
The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies. To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds. Access to most tools on the Cisco Support website requires a Cisco.com user ID and password. |
Release | Modification |
---|---|
Cisco IOS 15.0(2)EX1 |
This feature was introduced. |