Understanding Nexus -- Part 12 -- VLAN Configs

VLANs provide layer-2 separation boundaries for unicast, multicast, and broadcast packets. Even on Nexus the VLAN configuration is just as same as in IOS.

There are some facts which I would like to update you first.

• Each VDC supports 4094 VLANs.  VLANs 3968-4047 and 4094 are reserved for internal use.
• VLANs 1 – 3967 and 4048 – 4094 are configurable (3968-4047 and 4094 are reserved for internal use – The CLI will not let you configure them)
• VLAN 1 is the default VLAN and cannot be deleted
• Once a VLAN is created, it automatically goes in the “active” state - Use the shutdown command to disable a VLAN
• VLAN 1006 – 3967 and 4048 – 4093 cannot be disabled with the shutdown or the state suspend command – they are always “active”
• 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 re-create, that specified VLAN, the system automatically reinstates all the original ports to that VLAN.
• Commands entered in the VLAN configuration submode are immediately executed.

Here is a short table for your reference.

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—3967 and 4048—4093	Extended	You can create, name, and use these VLANs. You cannot change the following parameters: The state is always active. The VLAN is always enabled. You cannot shut down these VLANs.
3968-4047 and 4094	Internally allocated	These 80 VLANs and VLAN 4094 are allocated for internal device use. You cannot create, delete, or modify any VLANs within the block reserved for internal use.

Configuring VLAN


There are lot of options you can configure for VLAN. Here is the output for VLAN config-mode.

switch(config)# vlan 10
switch(config-vlan)# ?
  ip              Configure IP features
  media           Media type of the VLAN
  name            Ascii name of the VLAN
  no              Negate a command or set its defaults
  remote-span     Enable remote span VLAN
  service-policy  Configure service policy for an interface
  shutdown        Shutdown VLAN switching
  state           Operational state of the VLAN
switch(config-vlan)# name email-vlan
switch(config-vlan)# state active
switch(config-vlan)# no shutdown
switch(config-vlan)# vlan 11-19         --- To configure a range
switch(config-vlan)# vlan 20,30         --- To configure a range