Operation Manual – DHCPH3C S5600 Series Ethernet Switches Chapter 1 DHCP Overview1-41.3 DHCP Packet FormatDHCP has eight types of packets. They have the same format, but the values of somefields in the packets are different. The DHCP packet format is based on that of theBOOTP packets. The following figure describes the packet format (the number in thebrackets indicates the field length, in bytes):Figure 1-2 DHCP packet formatThe fields are described as follows:z op: Operation types of DHCP packets, 1 for request packets and 2 for responsepackets.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 eachDHCP relay agent that the DHCP request packet passes, the field value increasesby 1.z xid: Random number that the client selects when it initiates a request. The numberis 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 DHCPresponse packet is a unicast (set to 0) or broadcast (set to 1). Other bits arereserved.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 afterit sent the request packet.z chaddr: Hardware address of the DHCP client.z sname: Name of the DHCP server.
