DHCP Scope - The available IP address range as well as excluded addresses, subnet mask, lease durations, and other options.

DHCP Pools - Groupings of IP addresses (within scope)

• Each subnet has its own scope

Addresses given by DHCP have a "lease" period for which they will remain assigned to a device

A DHCP server will keep track of which mac addresses used which IPs and will assign a device the same IP it used before

Address reservation - We can manually link a particular IP address to a MAC address so that the device will always get that IP

DHCP Leases essentially auto renew:

• The device will check in with the DHCP server at two times to try to renew its IP:
  • T1: Once 50% of the lease time is up
  • T2: Once 87.5% (7/8) of the lease time is up

DHCP options - A special field in the DHCP message that includes many options

• 256 (254 usable) options
• 0 is pad, 255 is end
• Common options are subnet mask, DNS server, domain name, etc.
• Option 129: Call Server IP address
• Option 135: HTTP Proxy for phone-specific applications