VLANs in IOS and NX-OS

There are always limitations and system-reserved resources on network platforms.  For years, certain VLANs have been “off-limits” on IOS platforms.  With NX-OS, we also have “off-limit” VLANs, however they are different from the IOS counterparts.

VLANs in Cisco IOS

On IOS platforms, we’re able to support VLAN IDs from 1 to 4094, however there are some reserved (not modifiable) VLANs within this range.  The following table shows a summary of the VLANs on most IOS platforms:

VLAN ID Range Usable? Can delete?
0 Reserved No – system use only No – you can’t see it
1 Normal Yes – default VLAN No
2-1001 Normal Yes Yes
1002-1005 Normal Yes No
1006-4094 Extended Yes Yes
4095 Reserved No – system use only No – you can’t see it

VLANs in Cisco NX-OS

As part of the cleanup of protocol support on NX-OS, we no longer have to worry about FDDI and Token Ring!  This and other factors (architectural?) leave us with a different set of usable/customizable VLANs on NX-OS:

VLAN ID Range Usable? Can delete?
1 Normal Yes – default VLAN No
2-1005 Normal Yes Yes
1006-3967 Extended Yes Yes
3968-4047 Internally Allocated No – system use only No
4048-4093 Extended Yes Yes
4094 Internally Allocated No – system use only No

Although the NX-OS configuration guide doesn’t mention VLANs 0 and 4095, I suspect that they could be there as there are many IOS similarities between the two systems.  I have no proof of this, so it’s just a guess that they’re there, but invisible to us (just like on IOS), however I have nothing to found this hypothesis on other than IOS has it (not a very good argument for the theory).

Conclusion

When architecting L2 network designs, be sure to take into account the changes in which VLANs we can work with.

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