Dell Force10 S4820T S4820T Configuration Guide - Page 342

www.dell.com | support.dell.com DHCP Packet Format and Options DHCP uses UDP as its transport protocol. The server listens on port 67 and transmits to port 68; the client listens on port 68 and transmits to port 67. The configuration parameters are carried as options in the DHCP packet in Type, Length, Value (TLV) format; many options are specified in RFC 2132. To limit the number of parameters that servers must provide, hosts specify the parameters that they require, and the server sends only those; some common options are given in Table 14-1. Figure 14-1. DHCP Packet Format op htype hlen hops xid secs flags ciaddr yiaddr siaddr giaddr chaddr sname file options Code Length Value Table 14-1. Common DHCP Options Option Subnet Mask Router Domain Name Server Domain Name IP Address Lease Time DHCP Message Type Parameter Request List Renewal Time Rebinding Time End Code Description 1 Specifies the client's subnet mask. 3 Specifies the router IP addresses that may serve as the client's default gateway. 6 Specifies the DNS servers that are available to the client. 15 Specifies the domain name that clients should use when resolving hostnames via DNS. 51 Specifies the amount of time that the client is allowed to use an assigned IP address. 53 1: DHCPDISCOVER 2: DHCPOFFER 3: DHCPREQUEST 4: DHCPDECLINE 5: DHCPACK 6: DHCPNACK 7: DHCPRELEASE 8: DHCPINFORM 55 Clients use this option to tell the server which parameters it requires. It is a series of octets where each octet is DHCP option code. 58 Specifies the amount of time after the IP address is granted that the client attempts to renew its lease with the original server. 59 Specifies the amount of time after the IP address is granted that the client attempts to renew its lease with any server, if the original server does not respond. 255 Signals the last option in the DHCP packet. 342 | Dynamic Host Configuration Protocol (DHCP)