Options and identification strings can be configured on several levels.
DHCP servers support the following options, as defined in RFC 2132:
Option 1 - Subnet Mask
Option 3 - Default Routers
Option 6 - DNS Name Servers
Option 12 - Host Name
Option 15 - Domain Name
Option 44 - Netbios Name Server
Option 46 - Netbios Node Type Option
Option 50 - IP Address
Option 51 - IP Address Lease Time
Option 53 - DHCP Message Type
Option 54 - DHCP Server IP Address
Option 55 - Parameter Request List
Option 58 - Renew (T1) Timer
Option 59 - Renew (T2) Timer
Option 60 - Class Identifier
Option 61 - Client Identifier
DHCP servers also support Sub-option 13 Relay Agent Information Option 82 as specified in RFC 3046, to enable the use of a pool indicated by the DHCP client.
These options are copied into the DHCP reply message, but if the same option is defined several times, the order of priority is the following:
subnet option
pool options
options from the DHCP client request
A local DHCP server must be bound to a specified interface by referencing the server from that interface. The DHCP server is then addressable by the IP address of that interface. A normal interface or a loop-back interface can be used.
A DHCP client is defined by the MAC address and the circuit identifier. This implies that for a specific combination of MAC and circuit identifier, only one IP address can be returned; if more than one request is made, the same address is returned.