31 Days Before Your CCNA Exam

Day 20 131Primary Dns Suffix . . . . . . . :Node Type . . . . . . . . . . . . : HybridIP Routing Enabled. . . . . . . . : NoWINS Proxy Enabled. . . . . . . . : NoEthernet adapter Local Area Connection:Connection-specific DNS Suffix . : cisco.comDescription . . . . . . . . . . . : Intel(R) PRO/1000 PLPhysical Address. . . . . . . . . : 00-16-41-AE-A5-A7Dhcp Enabled. . . . . . . . . . . : YesAutoconfiguration Enabled . . . . : YesIP Address. . . . . . . . . . . . : 192.168.10.11Subnet Mask . . . . . . . . . . . : 255.255.255.0Default Gateway . . . . . . . . . : 192.168.10.1DHCP Server . . . . . . . . . . . : 192.168.10.1DNS Servers . . . . . . . . . . . : 192.168.50.195209.165.202.158Primary WINS Server . . . . . . . : 192.168.10.254Lease Obtained. . . . . . . . . . : Wednesday, July 16, 2008 8:16:59 AMLease Expires . . . . . . . . . . : Friday, July 18, 2008 8:16:59 AMC:\>To release the DHCP configuration on a Windows-based client, enter the commandipconfig/release. To renew the DHCP configuration, enter the command ipconfig/renew.In a complex network, the DHCP servers are usually contained in a server farm. Therefore, clientstypically are not on the same subnet as the DHCP server, as shown in the previous example. Toensure broadcasted DHCPDISCOVER messages are sent to the remote DHCP server, use the iphelper-address address command.For example, in Figure 20-6 the DHCP server is located on the 192.168.11.0/24 LAN and is servingIP addressing information for both LANs.Without the ip helper-address command, R1 would discard any broadcasts from PC1 requestingDHCP services. To configure R1 to relay DHCPDISCOVER messages, enter the following command:R1(config)#interface fastethernet 0/0R1(config-if)#ip helper-address 192.168.11.5Notice the command is entered on the interface that will receive DHCP broadcasts. R1 then forwardsDHCP broadcast messages as a unicast to 192.168.11.5. The ip helper-address commandby default forwards the following eight UDP services:■■■■Port 37: TimePort 49: TACACSPort 53: DNSPort 67: DHCP/BOOTP client