Configuring VLANs

This chapter contains the following sections:

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Information About VLANs

Understanding VLANs

A VLAN is a group of end stations in a switched network that is logically segmented by function, project team, or application, without the limitation 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 port can belong to a VLAN; all unicast, broadcast, and multicast packets are forwarded and flooded only to end stations in that VLAN. Each VLAN is considered a logical network. If a packet destination address does not belong to the VLAN, it must be forwarded through a router.

The following figure shows VLANs as logical networks. In this diagram, the stations in the engineering department are assigned to one VLAN, the stations in the marketing department are assigned to another VLAN, and the stations in the accounting department are assigned to yet another VLAN.

Figure 1. VLANs as Logically Defined Networks

VLANs are usually associated with IP subnetworks. For example, all the end stations in a particular IP subnet belong to the same VLAN. To communicate between VLANs, you must route the traffic.

By default, a newly created VLAN is operational. To disable the VLAN use the shutdown command. Additionally, you can configure VLANs to be in the active state (passing traffic), or the suspended state (in which the VLANs are not passing packets). By default, the VLANs are in the active state and pass traffic.


Note

The VLAN Trunking Protocol (VTP) mode is OFF. VTP BPDUs are dropped on all interfaces of the switch. This process has the effect of partitioning VTP domains if other switches have VTP turned on.

A VLAN can also be configured as a switched virtual interface (SVI). In this case, the switch ports in the VLAN are represented by a virtual interface to a routing or bridging system. The SVI can be configured for routing, in which case it supports Layer 3 protocols for processing packets from all switch ports associated with the VLAN, or for in-band management of the switch.

Understanding VLAN Ranges

The Cisco Nexus device supports VLAN numbers 1 to 4094 in accordance with the IEEE 802.1Q standard. These VLANs are organized into ranges. The switch is physically limited in the number of VLANs it can support. The hardware also shares this available range with its VSANs. For information about VLAN and VSAN configuration limits, see the configuration limits documentation for your device.

The following table describes the details of the VLAN ranges.

Table 1. VLAN Ranges

VLANs Numbers

Range

Usage

1

Normal

Cisco default. You can use this VLAN, but you cannot modify or delete it.

2—1005

Normal

You can create, use, modify, and delete these VLANs.

1006—4094

Extended

You can create, name, and use these VLANs. You cannot change the following parameters:

  • State is always active.

  • VLAN is always enabled. You cannot shut down these VLANs.

3968—4049 and 4094

Internally allocated

These 82 VLANs, plus VLAN 4094, are allocated for internal use. You cannot create, delete, or modify any VLANs within the block reserved for internal use.


Note

You cannot configure the internally allocated VLANs (reserved VLANs).


Note

VLANs 3968 to 4049 and 4094 are reserved for internal use; these VLANs cannot be changed or used.

Cisco NX-OS allocates a group of 82 VLAN numbers for those features, such as multicast and diagnostics, that need to use internal VLANs for their operation. By default, the system allocates VLANs numbered 3968 to 4049 for internal use. VLAN 4094 is also reserved for internal use by the switch.

You cannot use, modify, or delete any of the VLANs in the reserved group. You can display the VLANs that are allocated internally and their associated use.

Creating, Deleting, and Modifying VLANs

VLANs are numbered from 1 to 4094. All configured ports belong to the default VLAN when you first bring up the switch. The default VLAN (VLAN1) uses only default values. You cannot create, delete, or suspend activity in the default VLAN.

You create a VLAN by assigning a number to it. You can delete VLANs as well as move them from the active operational state to the suspended operational state. If you attempt to create a VLAN with an existing VLAN ID, the switch goes into the VLAN submode but does not create the same VLAN again.

Newly created VLANs remain unused until ports are assigned to the specific VLAN. All the ports are assigned to VLAN1 by default.

Depending on the range of the VLAN, you can configure the following parameters for VLANs (except the default VLAN):

  • VLAN name

  • Shutdown or not shutdown

When you delete a specified VLAN, the ports associated to that VLAN are shut down and no traffic flows. However, the system retains all the VLAN-to-port mapping for that VLAN, and when you reenable, or recreate, the specified VLAN, the system automatically reinstates all the original ports to that VLAN.


Note

Commands entered in the VLAN configuration submode are immediately executed.

VLANs 3968 to 4049 and 4094 are reserved for internal use; these VLANs cannot be changed or used.

About the VLAN Trunking Protocol

VLAN Trunking Protocol (VTP) is a distributed VLAN database management protocol that synchronizes the VTP VLAN database across domains. A VTP domain includes one or more network switches that share the same VTP domain name and are connected with trunk interfaces. Each switch can be in only one VTP domain. Layer 2 trunk interfaces, Layer 2 port channels, and virtual port channels (vPCs) support VTP functionality. You can configure VTP in client or server mode. In previous releases, VTP worked only in transparent mode.

The following are the different VTP modes:

  • Server mode—Allows users to perform configurations, manage the VLAN database version, and store the VLAN database.

  • Client mode—Does not allow users to perform configurations and relies on other switches in the domain to provide configuration information.

  • Off mode—Allows users to access the VLAN database (VTP is enabled) but does not participate in VTP.

  • Transparent mode—Does not participate in VTP, uses local configuration, and relays VTP packets to other forward ports. VLAN changes affect only the local switch. A VTP transparent network switch does not advertise its VLAN configuration and does not synchronize its VLAN configuration based on received advertisements.

Guidelines and Limitations for VTP

VTP has the following configuration guidelines and limitations:

  • When a switch is configured as a VTP client, you cannot create VLANs on the switch in the range of 1 to 1005.

  • VLAN 1 is required on all trunk ports used for switch interconnects if VTP is supported in the network. Disabling VLAN 1 from any of these ports prevents VTP from functioning properly.

  • If you enable VTP, you must configure either version 1 or version 2. On the Cisco Nexus device, 512 VLANs are supported. If these switches are in a distribution network with other switches, the limit remains the same.

    On the Cisco Nexus device, 512 VLANs are supported. If these switches are in a distribution network with other switches, the VLAN limit for the VTP domain is 512. If a Cisco Nexus device client/server receives additional VLANs from a VTP server, they transition to transparent mode.

  • If system vlan long-name knob is enabled, then VTP configurations will come up in OFF mode and users can change the mode to Transparent. However, changing the mode to Server or Client is not allowed.

  • The show running-configuration command does not show VLAN or VTP configuration information for VLANs 1 to 1000.

  • When deployed with vPC, both vPC switches must be configured identically. vPC performs a Type 2 consistency check for VTP configuration parameters.

  • VTP advertisements are not sent out on Cisco Nexus Fabric Extender ports.

  • Private VLANs (PVLANs) are supported only when the switch is in transparent mode.

  • If you are using VTP in a Token Ring environment, you must use version 2.

  • When a switch is configured in VTP client or server mode, VLANs 1002 to1005 are reserved VLANs.

  • VTPv3 pruning is supported from Cisco NX-OS Release 7.2(0)N1(1) onwards.

  • You must enter the copy running-config startup-config command followed by a reload after changing a reserved VLAN range. For example: 

    switch(config)# system vlan 2000 reserve 
This will delete all configs on vlans 2000-2081. Continue anyway? (y/n) [no] y

    After the switch reload, VLANs 2000 to 2081 are reserved for internal use, which requires that you enter the copy running-config startup-config command before the switch reload. Creating VLANs within this range is not allowed.

  • In SNMP, the vlanTrunkPortVtpEnabled object indicates whether the VTP feature is enabled or not.

Configuring a VLAN

Creating and Deleting a VLAN

You can create or delete all VLANs except the default VLAN and those VLANs that are internally allocated for use by the switch. Once a VLAN is created, it is automatically in the active state.


Note

When you delete a VLAN, ports associated to that VLAN shut down. The traffic does not flow and the packets are dropped.

Procedure

  Command or Action Purpose
Step 1

switch# configure terminal

Enters global configuration mode.

Step 2

switch(config)# vlan {vlan-id | vlan-range}

Creates a VLAN or a range of VLANs.

If you enter a number that is already assigned to a VLAN, the switch moves into the VLAN configuration submode for that VLAN. If you enter a number that is assigned to an internally allocated VLAN, the system returns an error message. However, if you enter a range of VLANs and one or more of the specified VLANs is outside the range of internally allocated VLANs, the command takes effect on only those VLANs outside the range. The range is from 2 to 4094; VLAN1 is the default VLAN and cannot be created or deleted. You cannot create or delete those VLANs that are reserved for internal use.

Step 3

switch(config-vlan)# no vlan {vlan-id | vlan-range}

Deletes the specified VLAN or range of VLANs and removes you from the VLAN configuration submode. You cannot delete VLAN1 or the internally allocated VLANs.

Example

This example shows how to create a range of VLANs from 15 to 20: 

switch# configure terminal
switch(config)# vlan 15-20

Note

You can create and delete VLANs in the VLAN configuration submode.

Configuring VLAN Long-Name


Note

If VTP is enabled, it must be in transparent or in off mode. VTP cannot be in client or server mode. For more details about VTP, see the Configuring VTP chapter.

Beginning with Cisco NX-OS Release 7.3(0)N1(1), the length of VLAN name that you can configure is increased from 32 to 128 characters. In the earlier release version, you could configure the length of VLAN name up to 32 characters.

Procedure

Step 1

configure terminal

Example:

switch# configure terminal

Enters global configuration mode.

Step 2

system vlan long-name

Example:

switch(config)# system vlan long-name

Allows you to configure the length of VLAN names up to 128 characters.

Note 

Enabling or disabling the system vlan long-name command will trigger a system log message that will let you know if the VLAN long name is enabled or disabled.

If you try to enable or disable the system vlan long-name command, when it is already enabled or disabled, the system will throw error message. We recommend you view the status of the VLAN long-name knob before enabling or disabling this command.

Use the no form of this command to disable this feature.

Step 3

(Optional) copy running-config startup-config

Example:

switch(config)# copy running-config startup-config

Saves the change persistently through reboots and restarts by copying the running configuration to the startup configuration.

Step 4

show running-config | sec long-name

Example:

switch(config)# show running-config | sec long-name
Displays the VLAN long-name status information.
Note 

When you configure a VLAN name of more than 32 characters, the show vlan commands will show the output in mulitple lines with each line containing a maximum of 32 characters.

Example

This example shows how to configure VLAN long-names of up to 128 characters. 
switch# configure terminal
switch(config)# system vlan long-name
!2001 Sep 29 02:24:11 N72-3 %$ VDC-1 %$ %VLAN_MGR-2-CRITICAL_MSG: VLAN long name is Enabled!
switch(config)# copy running config startup config
switch(config)# show running-config | sec long-name 
switch# configure terminal
switch(config)# vlan 2
switch(config-vlan)# name VLAN128Char000000000000000040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002

switch(config-vlan)# exit
switch# show vlan id 2

VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
2 VLAN128Char000000000000000040000 active 
00000000000000000000000000000000 
00000000000000000000000000000000 
00000000000000000000000000000002 
.
.
.

The following example displays the error output if you try to configure a VLAN long name of more than 128 characters. 

switch# system vlan long-name
switch(config)# vlan 2
switch(config-vlan)# name 129Char123456789000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000987654321CiscoBangalore

!% String exceeded max length of (128) at '^' marker.!
Switch(config-vlan)# exit

The following example displays the error output if you try to configure VLAN name ( more than 32 characters) without enabling the system vlan long- name command. 

switch# configure terminal
switch(config)# vlan 2
switch(config-vlan)# name 33Char1234567890987CiscoBangalore
!ERROR: Long VLAN name is not enabled: Vlan name greater than 32 is not allowed!
Switch(config-vlan)# exit

Changing the Range of Reserved VLANs

To change the range of reserved VLANs, you must be in global configuration mode. After entering this command, you must do the following tasks:

  • Enter the copy running-config startup-config command

  • Reload the device

Procedure

  Command or Action Purpose
Step 1

config t

Example:

switch# config t
switch(config)#

Enters global configuration mode.

Step 2

system vlan start-vlan reserve

Example:

switch(config)# system vlan 3968 reserve

Allows you to change the reserved VLAN range by specifying the starting VLAN ID for your desired range.

You can change the reserved VLANs to any other 82 contiguous VLAN ranges. When you reserve such a range, it frees up the range of VLANs that were allocated for internal use by default, and all of those VLANs are available for user configuration except for VLAN 4094.

Note 

To return to the default range of reserved VLANs (3968-4049 and 4094), you must enter the no system vlan start-vlan reserve command.

Step 3

copy running-config startup-config

Example:

switch(config)# copy running-config
startup-config

Copies the running configuration to the startup configuration.

Note 

You must enter this command if you change the reserved block.

Step 4

reload

Example:

switch(config)# reload

Reloads the software, and modifications to VLAN ranges become effective.

For more details about this command, see the Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 6.x.

Step 5

(Optional) show system vlan reserved

Example:

switch(config)# show system vlan reserved
 (Optional)

Displays the configured changes to the VLAN range.

Example

This example shows how to change the range of reserved VLANs: 

switch# configuration terminal
switch(config)# system vlan 1006 reserve
This will delete all configs on vlans 1006-1087. Continue anyway? (y/n) [no] yes 
Note: After switch reload, VLANs 1006-1087 will be reserved for internal use.
      This requires copy running-config to startup-config before
      switch reload.  Creating VLANs within this range is not allowed.
switch(config)# copy running-config startup-config
switch(config)# reload
switch(config)# show system vlan reserved

Note

You must reload the device for this change to take effect.

Configuring a VLAN

To configure or modify the VLAN for the following parameters, you must be in the VLAN configuration submode:

  • Name


    Note
    VLAN name can be either a short name (up to 32 characters) or long name (up to 128 characters). To configure VLAN long-name of up to 128 characters, you must enable system vlan long-name command.

  • Shut down


Note

You cannot create, delete, or modify the default VLAN or the internally allocated VLANs. Additionally, some of these parameters cannot be modified on some VLANs.

Procedure

  Command or Action Purpose
Step 1

switch# configure terminal

Enters global configuration mode.

Step 2

switch(config)# vlan {vlan-id | vlan-range}

Enters VLAN configuration submode. If the VLAN does not exist, the system first creates the specified VLAN.

Step 3

switch(config-vlan)# name vlan-name

Names the VLAN. You can enter up to 32 alphanumeric characters to name the VLAN. You cannot change the name of VLAN1 or the internally allocated VLANs. The default value is VLANxxxx where xxxx represents four numeric digits (including leading zeroes) equal to the VLAN ID number.

Step 4

switch(config-vlan)# state {active | suspend}

Sets the state of the VLAN to active or suspend. While the VLAN state is suspended, the ports associated with this VLAN are shut down, and that VLAN does not pass any traffic. The default state is active. You cannot suspend the state for the default VLAN or VLANs 1006 to 4094.

Step 5

(Optional) switch(config-vlan)# no shutdown

(Optional)

Enables the VLAN. The default value is no shutdown (or enabled). You cannot shut down the default VLAN, VLAN1, or VLANs 1006 to 4094.

Example

This example shows how to configure optional parameters for VLAN 5: 

switch# configure terminal
switch(config)# vlan 5
switch(config-vlan)# name accounting
switch(config-vlan)# state active
switch(config-vlan)# no shutdown

Adding Ports to a VLAN

After you have completed the configuration of a VLAN, assign ports to it.

Procedure

  Command or Action Purpose
Step 1

switch# configure terminal

Enters global configuration mode.

Step 2

switch(config)# interface {ethernet slot/port | port-channel number}

Specifies the interface to configure, and enters the interface configuration mode. The interface can be a physical Ethernet port or an EtherChannel.

Note 

If this is a QSFP+ GEM or a breakout port, the port syntax is QSFP-module/port .

Step 3

switch(config-if)# switchport access vlan vlan-id

Sets the access mode of the interface to the specified VLAN.

Example

This example shows how to configure an Ethernet interface to join VLAN 5:

switch# configure terminal

switch(config)# interface ethernet 1/13

switch(config-if)# switchport access vlan 5

Configuring VTP

You can configure VTP in the client or server mode on Cisco Nexus devices.

You can enable VTP and then configure the VTP mode (server [default], client, transparent, or off). If you enable VTP, you must configure either version 1 or version 2. If you are using VTP in a Token Ring environment, you must use version 2.

Procedure

  Command or Action Purpose
Step 1

switch# configure terminal

Enters global configuration mode.

Step 2

switch(config)# feature vtp

Enables VTP on the device. The default is disabled.

Step 3

switch(config)# vtp domain domain-name

Specifies the name of the VTP domain that you want this device to join. The default is blank.

Step 4

switch(config)# vtp version {1 | 2}

Sets the VTP version that you want to use. The default is version 1.

Step 5

switch(config)# vtp mode {client | server| transparent| off}

Sets the VTP mode to client, server, transparent, or off.

You can configure VTP in client or server mode.

Step 6

switch(config)# vtp file file-name

Specifies the ASCII filename of the IFS file system file where the VTP configuration is stored.

Step 7

switch(config)# vtp password password-value

Specifies the password for the VTP administrative domain.

Step 8

switch(config)# exit

Exits the configuration submode.

Step 9

(Optional) switch# show vtp status

(Optional)

Displays information about the VTP configuration on the device, such as the version, mode, and revision number.

Step 10

(Optional) switch# show vtp counters

(Optional)

Displays information about VTP advertisement statistics on the device.

Step 11

(Optional) switch# show vtp interface

(Optional)

Displays the list of VTP-enabled interfaces.

Step 12

(Optional) switch# show vtp password

(Optional)

Displays the password for the management VTP domain.

Step 13

(Optional) switch# copy running-config startup-config

(Optional)

Copies the running configuration to the startup configuration.

Example

This example shows how to configure VTP in transparent mode for the device: 

switch# config t
switch(config)# feature vtp 
switch(config)# vtp domain accounting 
switch(config)# vtp version 2 
switch(config)# vtp mode transparent
switch(config)# exit 
switch#

This example shows the VTP status and that the switch is capable of supporting Version 2 and that the switch is running Version 1: 

switch(config)# show vtp status
VTP Status Information
----------------------
VTP Version                     : 2 (capable)
Configuration Revision          : 0
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 502
VTP Operating Mode              : Transparent
VTP Domain Name                 :
VTP Pruning Mode                : Disabled (Operationally Disabled)
VTP V2 Mode                     : Disabled
VTP Traps Generation            : Disabled
MD5 Digest                      : 0xF5 0xF1 0xEC 0xE7 0x29 0x0C 0x2D 0x01
Configuration last modified by 60.10.10.1 at 0-0-00 00:00:00
VTP version running             : 1

Verifying the VLAN Configuration

Use one of the following commands to verify the configuration:

Command

Purpose
switch# show running-config vlan [vlan_id | vlan_range]

Displays VLAN information.
switch# show vlan [brief | id [vlan_id | vlan_range] | name name | summary ]

Displays selected configuration information for the defined VLAN(s).
switch# show system vlan reserved

Displays the system reserved VLAN range.

Feature History for Configuring VLANs

This table lists the release history for this feature.

Note 

The feature history table is added/updated in this guide from Cisco Nexus Release 7.3(0)N1(1) onwards.

Table 2. Feature History for Configuring VLANs

Feature Name

Releases

Feature Information

Configure VLAN long-name.

7.3(0)N1(1)

You can configure VLAN long-names of up to 128 characters. The following command was introduced:

  • system vlan long-name