VTP - Client can't modify VLANs
When configuring VTP, a switch that is configured as a client cannot make any changes to VLANs. This is the case for all versions of VTP.
If an attempt is made to make such a change, the following error message appears:
%VTP VLAN configuration not allowed when device is in CLIENT mode.
Only VTP servers can make changes. In the case of VTPv3, only primary servers can make such changes.
Links
https://forum.networklessons.com/t/introduction-to-vtp-vlan-trunking-protocol/870/191?u=lagapidis
https://networklessons.com/switching/introduction-to-vtp-vlan-trunking-protocol