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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