The DHCP_SERVER_SPECIFIC_STRINGS structure defines the names of the default user class and vendor class.

 typedef struct _DHCP_SERVER_SPECIFIC_STRINGS {
   LPWSTR DefaultVendorClassName;
   LPWSTR DefaultUserClassName;
 } DHCP_SERVER_SPECIFIC_STRINGS,
  *LPDHCP_SERVER_SPECIFIC_STRINGS;

DefaultVendorClassName: A pointer, of type LPWSTR, to a null-terminated Unicode string that contains the name of the default vendor class. The maximum number of characters allowed in this string is 255, which includes the terminating null character.

DefaultUserClassName: A pointer, of type LPWSTR, to a null-terminated Unicode string that contains the name of the default user class.  The maximum number of characters allowed in this string is 255, which includes the terminating null character.