ccna r&s v6 pdf

ccna r&s v6 pdf.When obtaining addressing information, the DHCP client goes through the following four steps.1. Client generatesDHCPDISCOVER local broadcast to explore which DHCP servers are available on the LAN segment. -2. all of the network segments in theDHCP servers may respond to a client using a DHCPOFFER unicast message, thereby providing IP addressing information to the client. If the client receives a message from more than one server, it will select one of them (usually the first one). The DHCPOFFER message sent by the server to the client contains the following information: the IP address of the client, the subnet mask of the current network segment, the IP address of the default gateway, the DNS domain name, the address of the DNS server, the address of the WINS server, and the address of the TFTP server. Note that not all the information in the DHCPOFFER message is listed here.After selecting an offer, the client sends a DHCPREQUEST message to the appropriate server indicating that it wants to use the addressing information sent by that server. If there is only one server and the information provided by that server conflicts with the client's configuration, the client responds with a DHCPDECLINE message.The DHCP server responds with a DHCPACK message, which is an acknowledgement to the client that the server has received a DHCPREQUEST message and knows that the client has accepted the offered addressing information. The server may also respond with a DHCPNACK message, which tells the client that the previous offer is no longer valid and that the client must re-request the addressing information. This can occur if the client responds with a DHCPREQUEST message long after the server has sent a DHCPOFFER message.Remember the four steps that DHCP goes through when a client requests addressing information, and the information that a DHCPOFFER message might contain: a 1P address and a subnet mask; a default gateway; the addresses of DNS servers, TFTP servers, and WINS servers; and a domain name. Most DHCP server implementations specify a limited lease period: when the lease period is up, the client must send a renewal request (DHCPREQUEST) to continue using the original address or to obtain a new address.When a client shuts down normally, it can generate a DHCPRELEASE message to tell the server that it no longer needs the IP address assigned to it. Most DHCP configurations include a lease period that specifies how long the client can use the address. When the lease period is up, the client must renew the lease or obtain new IP addressing information from the current server.Configuring a Cisco router as a DHCP server is discussed in Chapter 17.