The non-negotiate option must be configured for trunk links between external physical switches and virtual switches in VST mode.

In order to communicate with virtual switches in VST mode, external switch ports must be configured as trunk ports. VST mode does not support Dynamic Trunking Protocol (DTP), so the trunk must be static and unconditional. The auto or desirable physical switch settings do not work with the ESXi Server because the physical switch communicates with the ESXi Server using DTP. The non-negotiate and on options unconditionally enable VLAN trunking on the physical switch and create a VLAN trunk link between the ESXi Server and the physical switch. The difference between non-negotiate and on options is that on mode still sends out DTP frames, whereas the non-negotiate option does not. The non-negotiate option should be used for all VLAN trunks, to minimize unnecessary network traffic for virtual switches in VST mode.