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DHCP messages

Why is a DHCP OFFER message is destined to IP: 10.0.0.21 (which was assigned to my PC by DHCP server later) before even the system configured it? When the host is still asking for an IP address, how can server send a unicast message. The host's IP address will still be 0.0.0.0. So, can anyone explain this?

Rakesh Nittur
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  • This is explained quite well here - http://stackoverflow.com/questions/10636699/why-are-dhcp-offer-and-ack-broadcasted/10757849#10757849 – Paras Gera Nov 17 '16 at 11:33

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If you read RFC951 document , you see DHCP flow chart . any machine send DHCP DISCOVER in network . If "dhcp server" is exist in network , it send DHCP OFFER message as you see. So if client accept this ip , send DHCP REQUEST message(broadcast). Then dhcp server send ACK . So actually, server doesnt send unicast message.its Just offer . After 4 message, client ip will be 10.0.0.21

Y.Alyaprak
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