ARP Communication

Does DHCP use ARP only as commu开发者_开发百科nication protocol to assign an IP Address?

No ARP at all.

1.Client ff:ff:ff:ff:ff:ff 0.0.0.0 255.255.255.255 DHCP Discover

2.DHCPsrvr ff:ff:ff:ff:ff:ff 192.168.1.1 255.255.255.255 DHCP Offer

3.Client ff:ff:ff:ff:ff:ff 0.0.0.0 255.255.255.255 DHCP Request

4.DHCPsrvr mac address of client 192.168.1.1 192.168.1.102 DHCP ACK

1. Client send ethernet frame saying "where is the DhCP server?" so, he sends to broadcast MAC address, because he does not the mac address of dhcp. There can be several DHCP servers. He has no ip, so in the IP packet source is 0.0.0.0. Destination IP reflects Destination MAC => Broadcast

2. Server answers with an unicast IP (OFFER), a default gateway, a DNS & other options. Since the host has not yet agreed anything with the DHCP server, the DHCP serv. will send a broadcast frame.

3. Client officially requests (REQ) the IP lease from the server. Since no agreement has been made he just sends a broadcast. from 0.0.0.0 since he stills has no confirmed IP address.

4. Server acknowledges it(ACK), from its own mac address, from its own IP, to the IP of the host with the MAC address of the host.

No. Read this page, and if you'll have further questions, ask.

When DHCP Server assign a IP Address to DHCP Client, Server use broadcast to let Client and other DHCP Servers, which is located in the same local network(There may be more than one DHCP Server in the local network), know this offered IP Address. However, it could be some ARP packets during DISCOVER/ OFFER/ REQUEST/ ACK, because Client Server want to know whether this offered IP Address is available in the local network.