\section{Process} \fig{dhcp/dhcpdiscoverprocess}{dhcpdiscoverprocess}{DHCP Discover Process} \subsection{DHCP Messages} \begin{itemize} \item \textbf{DHCPDECLINE:} Message sent from the client to the server that the address is already in use. \item \textbf{DHCPNAK:} The server sends a refusal to the client for request for configuration. \item \textbf{DHCPRELEASE:} Client tells a server that it is giving up a lease. \item \textbf{DHCPINFORM:} A client already has an IP address but is requesting other configuration parameters that the DHCP server is configured to deliver such as DNS address. \end{itemize} \section{Example configuration} \subsection{Cisco} \begin{txt} ip dhcp excluded-address 192.168.0.254 ! ip dhcp pool LAN-1-POOL-DHCP network 192.168.0.0 255.255.255.0 default-router 192.168.0.254 lease 2 ! set in days \end{txt} When configuring a Layer 3 interface as a relay port for DHCP request for a subnet. Set the ip helper command on the interface with one \textit{or} more ip addresses. \begin{txt} interface GigabitEthernet 0/3 ip helper-address 192.168.220.220 ip helper-address 192.168.222.222 \end{txt}