Benefits of Dynamic Host Configuration Protocol - Essay Example

Dynamic host configuration protocol (DHCP) Definition This is defined as a networking /client server protocol that enables client machines be assigned IP addresses automatically by the server from a given range of addresses in the given network. Traditionally, all the TCP/IP parameters were configured manually which is commonly referred to as static configuration. Every machine required an IP address, subnet mask and a default gateway be inputted manually. If one of the values was wrongly entered, it disrupted the communication and it was hard to quickly establish the cause. Advantages/ Benefits of DHCP 1. minimized IP Address configuration errors as is attributed with the manual IP address configurations to computers 2. Network administration tasks are reduced since the TCP/IP configurations are now centralized and automated, it’s easy to handle efficiently ip addresses for client machines whose IP addresses change frequently i.e. devise on wireless network. 3. There is no address duplication since there’s automatic assignment of IP addresses. Significance of DHCP All devices on a TCP/IP-based network are required to have unique IP addresses to help the computers access the network and share resources. Without using a DHCP, it means that IP addresses must be reconfigured anytime a computer is added or moved to a different subnet and similarly the IP addresses be reclaimed when a computer from the network. DHCP on the other hand comes in handy by automating the entire process as well as central management of the same. The DHCP protocol is contained in the DHCP server which holds a pool of IP addresses and leases the given IP addresses to client machines which join the network. It uses the concept of ‘lease’ or time length that a particular IP address remains valid. The DHCP is an extension of BOOTp protocol which is an earlier network IP management protocol. Implemeting a DHCP eliminates some of configuration problems associated with manually configured TCP/IP. Some of the parameters that are passed to a DHCP client include: The clients IP address A subnet mask Default gateway Domain Name Servers Network servers Time synchronization information. Manual TCP/IP addressing Configuration The limitations of configuring TCP/IP manually mean that: 1. It’s easy for users to pick a random IP address instead of getting a valid IP address. These incorrect IP addresses lead to network problems which become difficult to trace 2. Manually typing of IP addresses, subnet masks or default gateways leads to communication problems if the credentials are wrong. 3. There are administrative overheads on internetworks when computers are frequently changed between subnets. How DHCP works DHCP server offers an automated method for IP address distribution and updating on a given network. The server offers this information to the particular client through a series of message exchanges called DHCP conversations or DHCP transactions. For communication on different subnets, a DHCP relay agent is preferred to aid the conversation. DHCP Architecture A DHCP architecture consists of DHCP servers, DHCP clients and DHCP relay agents. The DHCP client is a network-enabled device that enables the communication with the DHCP server for the purpose of getting a dynamically leased IP address. DHCP is supported in the following operating systems: Windows NT version 4, Windows 2000, Windows XP, Windows server 2003, windows 98, windows ME. The DHCP Server is in charge of maintaining the scope, reservations as well as options as set by the given administrator. Configuring a DHCP client Normally the DHCP client TCP/IP software is never configured with a static IP address but instead configured to get/obtain the IP address dynamically from the DHCP server. The leasing process of TCP/IP configuration involves the following four steps: DHCPDISCOVER-the DHCP client will broadcast a DHCP discover message that contains its specific MAC address as well as the computer name in attempt to request for an IP address from any DHCP server that contains the configuration information. Since the client does not have an IP address or know the IP address of the DHCP server, it uses 0.0.0.0 as the source address and 255.255.255.255 as the destination address. DHCPOFFER-Each of the DHCP servers that receives the DHCP discover message will respond with a DHCP offer message to the client machine that issued the DHCPDISCOVER.The DHCP offer message will contain clients MAC address, offered IP address, subnet mask, length of the lease and IP address of DHCP server. Since multiple DHCP servers will be sending DHCP offer messages, the DHCP client only accepts the first DHCP that will arrive first. DHCP REQUEST-After the DHCP client accepts the offer it broadcasts a DHCPREQUEST datagram. The said datagram will hold the IP address of the server that issued the DHCPOFFER as well as the physical location of the client. The DHCPREQUEST message is used to request the selected server to now assign the client an IP address as well as other TCP/IP configurations settings. It also used to notify all other DHCP servers that the client did not accept their offers. DHCPACK- after the DHCP server receives the DHCPREQUEST message; it in turn constructs a DHCPACK message which is called DHCPACK (DHCP ACKNOWLEDGEMENT). The DHCPACK will contain the IP address as well as the subnet mask for the client. It holds other TCP/IP configurations like IP address of default gateway, IP address of DNS server, IP address of WINS server. DHCP LEASE RENEWAL- All DHCP clients will attempt to renew their lease when 50% of the lease time has expired. They request the DHCP server to allow it maintain the same IP address. This is what is referred to as lease renewal. To renew the lease, a DHCP client sends a DHCPREQUEST message to the DHCP server from which it obtained the lease. If the given server is available, it renews the lease and in turn sends the client a successful acknowledgement (DHCPACK) which now contains the new lease time as well as any configuration parameters that may have been updated. In the event a client may wish to renew the IP address but it’s not able to contact the DHCP server, the client receives a message indicating that the lease cannot be renewed and hence it can still use the address since 50% of the lease time is still available. Despite the renewal process being an automated process, the DHCP client can still manually initiate the process to renew a lease. The ipconfig/renew is used when a client wants to request a lease renewal. The ipconfig/release is used when the client want to release the given IP address lease. Planning DHCP Implementation Before the DHCP is actually implemented, there is need to perform proper planning. The following are some of the key activities one has to consider while thinking about a technical implementation of the DHCP. Range of addresses to distribute- The DHCP is capable of distributing a wide range of IP addresses, subnet masks, default gateways, DNS server addresses as well as WINS server addresses. Verify the layout of your network to determine if DHCP is desirable Network Layout- The number of DHCP servers required will be determined the network layout. A single DHCP server would be desirable for a single LAN network within a given building or location. In the case you are working with a large WAN, depending on the connection type, number of clients and the location of the connection, this may necessitate the need to have multiple DHCP servers to assist in address distribution. Addressing Scheme- You need to identify your network addressing scheme since each network has a unique addressing scheme. This should include knowing the IP addresses used, subnetting method used etc. Lease Duration-you need to identify whether the leased addresses should be leased for a longer period or a short period. This is determined by the nature of the work that the network performs. Again if the network consist of portable clients who connect and reconnect from the network often it’s useful to use the shorter lease periods. Static Assignment- It’s important to identify the given devices that should be allocated static addresses and those that should acquire dynamically. Devices such as routers, switches hubs, servers should be given static IP addresses for easy administration. Installing DHCP To begin with we need to select the Microsoft Windows NT Server within the organization and ensure that the server continues to use the static IP address after installation of the DHCP.From the control panel, double-click the network icon. From the network properties sheet, click on the services tab, click on the Add button to open the Select Network dialog box. Locate the Microsoft DHCP server from the provided network list and click ok. If there is a prompt to provide the location of the Microsoft Windows NT CD-ROM, provide the path to the Microsoft Windows NT installation files and click to continue. AS the Microsoft Windows NT finishes copying the files, it may prompt a warning message stating that any network adapter that’s using the dynamic IP addresses should immediately be changed to static IP addresses. Click on the OK button and the warning is now cleared. Finally close network properties and restart the computer. Considerations to make Before Configuring DHCP You need to provide at least one scope. The scope is defined as the range of the IP addresses that the server will assign the clients. You need to ensure that no two DHCP servers’ scope overlap since the DHCP server do not exchange information with each other. You need to leave some of the IP addresses outside the scope that should be reserved for servers i.e. the DHCP, DNS, WINS servers. Take note of the number of subnets you wish to have on your network. You can use a single DHCP server to service multiple subnets, but this is only possible if a router has been configured as a DHCP relay agent. A DHCP can only assign a scope to a given subnet. Works cited Droms, Ralph. “The DHCP handbook.” Indianapolis: Sams Publishers, 2003. Print. Read More