Internal Vlans in N7K

[ranjipremandrewp]

I did a 'show internal vlan usage' on a N7K and this is what I got.

SW1# show vlan internal usage

VLANs                   DESCRIPTION
-------------------     -----------------
3968-4031               Multicast
4032-4035,4048-4059     Online Diagnostic
4036-4039,4060-4087     ERSPAN
4042                    Satellite
3968-4095               Current

Can you please explain the meaning of each usage?

[ahmedshoaib]

Hi;

Beginning with Cisco release 5.2(1) for Cisco Nexus 7000 Series devices, VLANs 3968 to 4094 are reserved for internal use in each VDC by default.

You can change the reserved VLANs to any other 128 contiguous VLAN range. 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. All VDCs inherit the new reserved range of VLANs

To modify the system reserved vlan via below command:

system reserve vlan <vlan range>

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/layer2/configuration/guide/Cisco_Nexus_7000_Series_NX-OS_Layer_2_Switching_Configuration_Guide_Release_5-x_chapter4.html

Thanks & Best regards;

[ranjipremandrewp]

I want to understand the significance of each internal vlan

[ahmedshoaib]

Hi;

If you got the information please also share it on the group & this will be helpful for everyone.

Thanks & Best regards;

[sbhadrav@cisco.com]

The software allocates a group of VLAN numbers for features such as multicast and diagnostics that need to use internal VLANs for their operation. 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.

Beginning with Cisco NX-OS Release 5.2(1), the system allocates a block of 128 reserved VLANs (3968 to 4094) for these internal uses. You can change the block of 128 reserved VLANs to occupy another range of 128 adjacent VLANs. For example, you can change the reserved block of VLANs to be 400 to 528. You cannot assign a previously created VLAN as part of the 128 range of reserved VLANs. Anytime you change the reserved block of VLANs for the device, you must do the following:
Enter the copy running-configuration startup-configuration command
Reload the device
When you change the range of reserved VLANs, the existing configurations for the new range of VLANs get deleted. A warning note is displayed as in the following example:

switch(config)# system vlan 2000 reserve
This will delete all configs on vlans 2000-2127. Continue anyway? (y/n) [no] y
Note: After switch reload, VLANs 2000-2127 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)#