H3C Technologies H3C S3600 Series Switches - Manual (Page 639)

1-4
Figure 1-2 DHCP packet format
The fields are described as follows:
z op: Operation types of DHCP packets, 1 for request packets and 2 for response packets.
z htype, hlen: Hardware address type and length of the DHCP client.
z hops: Number of DHCP relay agents which a DHCP packet passes. For each DHCP relay agent
that the DHCP request packet passes, the field value increases by 1.
z xid: Random number that the client selects when it initiates a request. The number is used to
identify an address-requesting process.
z secs: Elapsed time after the DHCP client initiates a DHCP request.
z flags: The first bit is the broadcast response flag bit, used to identify that the DHCP response
packet is a unicast (set to 0) or broadcast (set to 1). Other bits are reserved.
z ciaddr: IP address of a DHCP client.
z yiaddr: IP address that the DHCP server assigns to a client.
z siaddr: IP address of the DHCP server.
z giaddr: IP address of the first DHCP relay agent that the DHCP client passes after it sent the
request packet.
z chaddr: Hardware address of the DHCP client.
z sname: Name of the DHCP server.
z file: Path and name of the boot configuration file that the DHCP server specifies for the DHCP
client.
z option: Optional variable-length fields, including packet type, valid lease time, IP address of a DNS
server, and IP address of the WINS server.
Protocol Specification
Protocol specifications related to DHCP include:
z RFC2131: Dynamic Host Configuration Protocol
z RFC2132: DHCP Options and BOOTP Vendor Extensions
z RFC1542: Clarifications and Extensions for the Bootstrap Protocol
z RFC3046: DHCP Relay Agent Information option