Right, the DHCP OFFER will be sent back as you observed. What the DHCP server is ignoring is the source IP address of the client making the request.
An interesting test to perform is to observe the IP offered by the DHCP server.
Is this different to the source IP in the client sending the DHCP DISCOVER message?
Also, it would be a good idea to perfom an ipconfig /release command from the client before captuting the DHCP DISCOVER message. Then force the request issuing a ipconfig /renew command
According to RFC2131, it is stated that the clients do not use any IP address while sending the DISCOVER messages though they can do so while sending the DHCPREQUEST message to renew their leases. However, I am getting the addressable IP as the source IP address of some of the machines while sending the DHCP DISCOVER messages.
Is it due to the TCP/IP stack that may be defined somewhat different in some operating systems?
Regarding your question: Is it due to the TCP/IP stack that may be defined somewhat different in some operating systems?
Yes, as I mentioned earlier. In my opinion it will depend on the particular implementation of the RFC by a specific network operating system as well as its version and flavor.
As Minikrao mentioned, it would not matter any way. That IP address will be ignored by the server when receiving the DCHP_DISCOVER message. I believe that a good implementation of the RFC would leave that value undefined, maybe just 0s.
Yes, When we install a new NIC to any machine and if we do not connect via LAN wire then also it has an IP assigned by the NIC vendor. Here are the links -