It is pretty standard practice to disable the default VLAN and renumber its tag ID for security reasons, from version 22.4 and above we often go this issue when performing these basic commands:
configure vlan "Default" delete ports all configure vlan Default tag 4000 disable vlan "Default"
We’d get the error as below. In our case we don’t want to run STP (Spanning Tree Protocol) because we’re using either EAPS or MLAG so its just not needed for loop prevention.
Error: VLAN Default cannot be disabled because it is configured for an L2 Protocol.
To resolve this you need to perform these steps before disabling the “Default” VLAN.
disable stpd s0 auto-bind vlan Default configure s0 delete vlan Default ports all disable vlan Default configure vlan Default tag 4000 configure vlan "Default" delete ports all
If you still get the same error, you may have already removed the “Default” VLAN from all ports, you first need to re-add the ports with: “configure vlan “Default” add ports all” then run the procedure above again. You’ll know the process when work when the “T” is removed from the flags column.
You can also try rebooting the switch, in theory the “T” flag should have disappeared when the switch has rebooted itself if even after performing the above steps you get the same error saying it can’t be disabled.