cisco 200-301 guide

cisco 200-301 guide.After Exam Essentials checks for address conflicts, the associated addresses are removed from the DHCP address pool and the problem is resolved manually by the administrator Be sure to familiarize yourself with the output of the command show ip dhcp conflictVideo 17.02.A multimedia demonstration of configuring and verifying a DHCP server on a Cisco router is included in the companion digital resource to this book.17.2.2 Configuring DHCP RelaysIn larger networks, network devices need to obtain addresses through DHCP, and the DHCP server is usually on a different subnet (broadcast domain) than the network devices. As stated in Chapter 5, clients use Layer 2 broadcasts to advertise DHCP requests. In most companies, DHCP servers are located at the distribution layer or data center, and routers do not forward broadcast messages by default, so DHCP does not see DHCP requests advertised by clients.The solution to this problem is to use IOS-capable DHCP relays, where the IOS routing device acts as a relay agent for DHCPREQUEST messages, as shown in Figure 17.2. In this figure, the router receives a request sent by the client as a broadcast and changes it to a unicast message with the source address of the current router and the destination address of the DHCP server, and includes the network number in it so that the DHCP server can select the correct address pool. All messages between the proxy and the DHCP server are transmitted using unicast. To the client, it appears as if it is communicating with a local DHCP server.To configure the router as a DHCP relay agent, use the following configuration.Router(config)# service dhcp Router(config)# interface type number Router(config)# ip helper-address DHCP_server_IP_addressDHCP DHCPClient server