The following show command under IOS/NX-OS will display these internal usage vlans;
show vlan internal usage
If you try to configure a vlan that's used internally, you will have an error similar to the below.
Now luck has it that cisco has created a means for reserving vlans. It's sometime best to apply this practices in big SP/ENTERPRISE networks to avoid design issues that could later conflicts with a reserved vlan.
Our socpuppets general thought has always been to craft vlans under the 4K range, and build a vlan allocation sheet that you SHOULD always review b4 vlan allocations.
The "vlan internal allocation policy ascending" or "vlan internal allocation policy descending" commands can help in determining the internal vlan allocation methods.
NOTE: I believe this is a IOS command and not widely deploy under most NX-OS switches.
NSE ( Network Security Expert) and Route/Switching Engineer.
kfelix -----a----t---- socpuppets ---dot---com
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