© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public ITE I Chapter 6 1 Implementing IP Addressing Services Accessing the WAN – Chapter 7 Cisco Thai Nguyen Networking Academy © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public ITE 1 Chapter 6 2 Objectives Configure DHCP in an enterprise branch network Configure NAT on a Cisco router Configure new generation RIP (RIPng) to use IPv6 Cisco Thai Nguyen Networking Academy © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public ITE 1 Chapter 6 3 Introducing DHCP Every device that connects to a network needs an IP address. Network administrators assign static IP addresses to routers, servers, and other network devices whose locations (physical and logical) are not likely to change. Administrators enter static IP addresses manually when they configure devices to join the network. Static addresses also enable administrators to manage those devices remotely. However, computers in an organization often change locations, physically and logically. Administrators are unable to keep up with having to assign new IP addresses every time an employee moves to a different office or cubicle. Desktop clients do not require a static address. Instead, a workstation can use any address within a range of addresses. This range is typically within an IP subnet DHCP assigns IP addresses and other important network configuration information dynamically. Because desktop clients typically make up the bulk of network nodes, DHCP is an extremely useful and timesaving tool for network administrators. RFC 2131 describes DHCP. Cisco Thai Nguyen Networking Academy © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public ITE 1 Chapter 6 4 Introducing DHCP Administrators typically prefer a network server to offer DHCP services, because these solutions are scalable and relatively easy to manage. However, in a small branch or SOHO location, a Cisco router can be configured to provide DHCP services without the need for an expensive dedicated server. A Cisco IOS feature set called Easy IP offers an optional, full-featured DHCP server. Cisco Thai Nguyen Networking Academy © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public ITE 1 Chapter 6 5 DHCP Operation Providing IP addresses to clients is the most fundamental task performed by a DHCP server. DHCP includes three different address allocation mechanisms to provide flexibility when assigning IP addresses: Manual Allocation: The administrator assigns a pre-allocated IP address to the client and DHCP only communicates the IP address to the device. Automatic Allocation: DHCP automatically assigns a static IP address permanently to a device, selecting it from a pool of available addresses. There is no lease and the address is permanently assigned to a device. Dynamic Allocation: DHCP automatically dynamically assigns, or leases, an IP address from a pool of addresses for a limited period of time chosen by the server, or until the client tells the DHCP server that it no longer needs the address. Cisco Thai Nguyen Networking Academy © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public ITE 1 Chapter 6 6 BOOTP vs. DHCP The Bootstrap Protocol (BOOTP), defined in RFC 951, is the predecessor of DHCP and shares some operational characteristics. BOOTP is a way to download address and boot configurations for diskless workstations. A diskless workstation does not have a hard drive or an operating system. For example, many automated cash register systems at your local supermarket are examples of diskless workstations Both DHCP and BOOTP are client/server based and use UDP ports 67 and 68. Those ports are still known as BOOTP ports. Cisco Thai Nguyen Networking Academy © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public ITE 1 Chapter 6 7 BOOTP vs. DHCP There are three primary differences between DHCP and BOOTP: The main difference is that BOOTP was designed for manual pre-configuration of the host information in a server database, while DHCP allows for dynamic allocation of network addresses and configurations to newly attached hosts. DHCP allows for recovery and reallocation of network addresses through a leasing mechanism. Specifically, DHCP defines mechanisms through which clients can be assigned an IP address for a finite lease period. This lease period allows for reassignment of the IP address to another client later, or for the client to get another assignment if the client moves to another subnet. Clients may also renew leases and keep the same IP address. BOOTP does not use leases. BOOTP provides a limited amount of information to a host. DHCP provides additional IP configuration parameters, such as WINS and domain name Cisco Thai Nguyen Networking Academy © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public ITE 1 Chapter 6 8 DHCP Server Configuration Cisco routers running Cisco IOS software provide full support for a router to act as a DHCP server. The Cisco IOS DHCP server assigns and manages IP addresses from specified address pools within the router to DHCP clients. Cisco Thai Nguyen Networking Academy © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public ITE 1 Chapter 6 9 Cisco Thai Nguyen Networking Academy © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public ITE 1 Chapter 6 10 [...]... manner The method used depends on the ISP However, in its simplest configuration, the Ethernet interface is used to connect to a cable modem To configure an Ethernet interface as a DHCP client, the ip address dhcp command must be configured In the figure, assume that an ISP has been configured to provide select customers with IP addresses from the 209.165.201.0 / 27 range The ouput confirms the assigned... Tasks in the Configure tab From the list of tasks, click on the DHCP folder and then select DHCP Pools to add a new pool Click Add to create the new DHCP pool ITE 1 Chapter 6 © 2006 Cisco Systems, Inc All rights reserved Cisco Public 17 Cisco Thai Nguyen Networking Academy DHCP Configuration with SDM The Add DHCP Pool window contains the options you need to configure the DHCP IP address pool The IP addresses... In the figure, the output of the show running-config command verifies that the DHCP relay IP address is referencing the DHCP server address at 192.168.11.5 Step 2 Verify that the global configuration command no service dhcp has not been configured This command disables all DHCP server and relay functionality on the router The command service dhcp does not appear in the configuration, because it is the. .. ITE 1 Chapter 6 © 2006 Cisco Systems, Inc All rights reserved Cisco Public 20 Cisco Thai Nguyen Networking Academy Verify DHCP Relay Follow these steps to verify the router configuration: Step 1 Verify that the ip helper-address command is configured on the correct interface It must be present on the inbound interface of the LAN containing the DHCP client workstations and must be directed to the correct... noticed that all the examples in this course use a somewhat restricted number of IP addresses You may also have noticed the similarity between these numbers and numbers you have used in a small network to view the setup web pages of many brands of printers, DSL and cable routers, and other peripherals These are reserved private Internet addresses drawn from the three blocks shown in the figure These addresses... 1918 private address In the figure, the IP address 192.168.10.10 is assigned to the host PC1 on the inside network Inside global address - Valid public address that the inside host is given when it exits the NAT router When traffic from PC1 is destined for the web server at 209.165.201.1, router R2 must translate the address In this case, IP address 209.165.200.226 is used as the inside global address... to the packet, and verify that routers have the correct routing information to move the packet Use the debug ip nat command to verify the operation of the NAT feature by displaying information about every packet that is translated by the router ITE 1 Chapter 6 © 2006 Cisco Systems, Inc All rights reserved Cisco Public 34 Cisco Thai Nguyen Networking Academy Reasons for Using IPv6 To comprehend the. .. administrators today, consider that the IPv4 address space provides approximately 4,294,9 67, 296 unique addresses Of these, only 3 .7 billion addresses are assignable because the IPv4 addressing system separates the addresses into classes and reserves addresses for multicasting, testing, and other specific uses Based on figures as recent as January 20 07, about 2.4 billion of the available IPv4 addresses are... ITE 1 Chapter 6 © 2006 Cisco Systems, Inc All rights reserved Cisco Public 14 Cisco Thai Nguyen Networking Academy DHCP Relay In a complex hierarchical network, enterprise servers are usually contained in a server farm These servers may provide DHCP, DNS, TFTP, and FTP services for the clients The problem is that the network clients typically are not on the same subnet as those servers Therefore, the. .. come from a NAT pool ITE 1 Chapter 6 © 2006 Cisco Systems, Inc All rights reserved Cisco Public 29 Cisco Thai Nguyen Networking Academy Configure NAT on a Cisco Router There are two possible ways to configure overloading, depending on how the ISP allocates public IP addresses In the first instance, the ISP allocates one public IP address to the organization, and in the other, it allocates more than . I Chapter 6 1 Implementing IP Addressing Services Accessing the WAN – Chapter 7 Cisco Thai Nguyen Networking Academy © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public ITE 1 Chapter. reassignment of the IP address to another client later, or for the client to get another assignment if the client moves to another subnet. Clients may also renew leases and keep the same IP address farm. These servers may provide DHCP, DNS, TFTP, and FTP services for the clients. The problem is that the network clients typically are not on the same subnet as those servers. Therefore, the