For example, if an IP address has been reserved for a specific MAC address then the IP will always be the IP reserved.īecause environments can have multiple DHCP servers the Transaction ID will determine which offer to accept. Available options are determined based on any reservations that may have been filed. For example, WINS is two options, 44 & 46 (server and type respectively) that can be provided to clients as is LDAP (option 95). In the second step, any DHCP servers that received the request will issue an offer, which includes a number of DHCP options, such as a subnet mask (option 1), a gateway (option 3), DNS servers (option 6), amount of time a lease is valid for (option 51), the IP of the DHCP server making the offer (option 54). The request also includes all of the options that the client will need, with options being anything beyond an IP address, each potential option with a numerical identifier per this list (defined in various RFPs). These typically remain local, although most routers will allow for configuring the gateway in such a way that UDP traffic is forwarded on to other subnets.

In the Discovery step, a computer that needs an IP address sends a broadcast request to the environment. In doing so, communications are comprised of 4 steps: Discovery, Offer, Acceptance, and Acknowledgment. DHCP is critical to a number of Mac OS X Server technologies, most notably with NetBoot.

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