On mixed VLAN mode devices, certain per-port features are not supported on S-VLANs that are supported on C-VLANs. Ports that are currently members of a regular VLAN can move to an S-VLAN only if there is no conflicting configuration.

When configuring S-VLAN port memberships using the svlan command, the CLI issues a warning and prompt if any of the ports listed already belong to a regular VLAN. For example:

HP Switch(config)#: svlan 200 tagged a1,a2
Ports a1, a2 will lose their cvlan memberships if any.
Do you want to continue: y/n?

The warning prompt is displayed only when there is at least one port in the port list that needs to be moved out from the C-VLAN space to the S-VLAN domain. Similarly, if ports being added to the C-VLAN are already members of an S-VLAN, the CLI issues a warning that the port's membership with its existing VLANs will be removed and will prompt for a confirmation before continuing.

If all ports are just being added or removed from within the same VLAN type domain, no prompt will appear. For example, moving ports from S-VLAN 200 to S-VLAN 300, will not result in any warning as the ports are already part of the S-VLAN domain.