The broadcast flag is an optional element of DHCP, but a client which sets it works only with a server or relay that supports it.
Microsoft Windows NT
DHCP client support added with version 3.5 sets the broadcast flag. Version 3.51 and later no longer set it. The exception is in the remote access support: it sets the flag when it uses DHCP to acquire addresses to hand out to its PPP clients.
tcp/ip-32 for Microsoft Windows for Workgroups (WFW)
Version 3.11a sets it, but version 3.11B doesn’t.
Microsoft Windows 95
Does not set the broadcast flag.