All Dynamic Host Configuration Protocol (DHCP) messages include a FIXED format section and a VARIABLE format section. The fixed format section consists of
several fields that are the same in every Dynamic Host Configuration Protocol (DHCP) message. The variable format section in the Dynamic Host Configuration Protocol (DHCP) contains "OPTIONS", which carry additional configuration parameters.
| DHCP Message Field |
Description |
| Operation Code | Specifies the type of the Dynamic Host Configuration Protocol (DHCP) message. Set to 1 in messages sent by a client (requests) and 2 in messages sent by a server (response). |
| Hardware Type | Specifies the network LAN architecture. For example, the ethernet type is specified when
htype is set to 1. |
| Hardware Address Length |
Link-layer address length (in bytes); defines the length of hardware address in
the chaddr field. For Ethernet, this value is 6. |
| Hops | Number of relay agents that have forwarded this message. |
|
Transaction identifier | Used by clients to match responses from servers with
previously transmitted requests. |
| seconds | Elapsed time (in seconds) since the client began theDynamic Host Configuration Protocol (DHCP) process. |
| Flags | Flags field is called the broadcast bit, can be set to 1 to
indicate that messages to the client must be broadcast |
| ciaddr | Client’s IP address; set by the client when the client has confirmed that its IP
address is valid. |
| yiaddr |
Client’s IP address; set by the server to inform the client of the client’s IP
address. |
| siaddr | IP address of the next server for the client to use in the configuration process
(for example, the server to contact for TFTP download of an operating
system kernel). |
| giaddr | Relay agent (gateway) IP address; filled in by the relay agent with the
address of the interface through which Dynamic Host Configuration Protocol (DHCP) message was received. |
| chaddr |
Client’s hardware address. (Layer 2 address) |
| sname | Name of the next server for client to use in the configuration process. |
| file | Name of the file for the client to request from the next server (for example
the name of the file that contains the operating system for this client). |
You have learned Dynamic Host Configuration Protocol (DHCP) Message Format and Dynamic Host Configuration Protocol (DHCP) Message fields in this lesson. Click "Next" to continue.
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