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Wireless Networking Handbook
(Publisher: Macmillan Computer Publishing)
Author(s): Jim Geier
ISBN: 156205631x
Publication Date: 09/01/96

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Addressing

If you plan to use applications requiring TCP/IP interfaces or if users need access to the Internet, you have to assign a unique Internet Protocol (IP) address to each device connected to the network (workstation, printer, server, and so forth). Actually, the IP address corresponds to a network connection, so a server having two network interface cards would require two IP addresses—one for each card.

The IP packet header contains the source and destination IP address that routers will use, along with a routing table, to determine where to send the packet next. The IP address is 32 bits long, allowing 4,294,967,296 unique IP addresses.

The developers of the Internet based IP addressing on the hierarchical format shown in figure 8.12, distinguishing the address into three classes: Class A, Class B, and Class C. If users never plan to interface with the Internet, then they are free to use the IP address space any way they want. Otherwise, they must obtain official IP addresses—unique from others assigned—to operate over the Internet. You can obtain an official IP address through an Internet Service Provider (ISP) in your nearest metropolitan area. The Network Information Center (NIC) allocates IP network addresses and registers domain names. Network Solutions, Inc. was awarded the contract for NIC registration services in the early 1990s. The service providers coordinate address assignment with Network Solutions. For an official IP address, you will be given a unique network number and be free to assign addresses within the domain. For example, if you are assigned a Class C address, you will be free to assign up to 255 addresses.


Figure 8.12  The Internet Protocol address hierarchy.

Address planning requires you to obtain enough official unique IP addresses for each network connection. For example, an organization having 350 users (each needing a network connection), 10 printers, and 4 servers would require at least 364 addresses. You could satisfy this requirement by obtaining one Class B address or two Class C addresses.


NOTE:  

Because of the vast number of organizations deploying Web servers and gaining access to the Internet, unique IP addresses are quickly running out. In fact, it’s impossible to obtain a Class A address and very difficult, if not impossible, to obtain a Class B address. You will probably need to be issued multiple Class C addresses. The problem, though, is that it is difficult to manage multiple Class C addresses if they are not contiguous. Therefore, you will need to predict the number of addresses needed in the future to obtain a contiguous series of addresses.


If your network implementation requires a large number of IP addresses, or it is difficult to predict the number of addresses needed in the future, consider private addressing. The NIC has set aside a single Class A address that you can use within your network, giving you a large number of addresses. You have to agree, however, to not use these addresses on the Internet. If you need Internet access, you can deploy a proxy server that translates your private addresses into legal Internet addresses. This means you need to obtain at least one Class C address to support the connections to the Internet.

The second task of address planning is to assign a part of the address (subnet number) to each LAN connected to a router port. This address will be configured within the router using a subnet mask. You will then need to assign a unique address, within the applicable subnet number, to each network connection.

For smaller LANs (less than 50 users), you can install the IP address within the applicable configuration files at each PC. For large LANs, consider the use of DHCP (Dynamic Host Configuration Protocol). DHCP issues IP addresses automatically within a specified range to devices such as PCs when they are first powered on. The device retains the use of the IP address for a specific license period that the system administrator can define. DHCP is available as part of the Microsoft Windows NT Server NOS, and offers these advantages over manual installation:

  Efficient implementation of address assignments. With DHCP, there is no need to manually install or change IP addresses at every client workstation during initial installation or when a workstation is moved from one location to another. This saves time during installation and eliminates mistakes when allocating addresses (such as duplicate addresses or addresses having the wrong subnet number). It is very difficult to track down address-related problems that may occur when using permanently assigned addresses. This advantage is greatest for larger networks.
  Central point of address management. With DHCP, there is no need to update the IP address at each client workstation if making a change to the network’s configuration or address plan. With DHCP, you can make these changes from a single point in the network. For example, if you move the domain name service software to a different platform, you need to incorporate that change for each client workstation if using permanently assigned addresses. With DHCP, you just update the configuration screen from a single point at the NT server or remote location. Again, this advantage is greatest for larger networks.

Network Management Protocols

In order to support effective network management, be sure to incorporate network management protocols into the design to support a network management system comprising the components shown in figure 8.13 and defined below.

  Network Elements. Network elements, sometimes called managed devices, are hardware devices such as computers, routers, and terminal servers that are connected to networks.
  Agents. Agents are software modules that reside in network elements. They collect and store management information, such as the number of error packets received by a network element.
  Management Information Base (MIB). A MIB is a collection of managed objects residing in a virtual information store.
  Network Management Stations (NMSs). An NMS executes management applications that monitor and control network elements.


Figure 8.13  The network management system.

The industry’s de facto standard for network management is Simple Network Management Protocol (SNMP), which facilitates the exchange of management information between network devices. By using SNMP to access management information data (such as packets per second and network error rates), network administrators can more easily manage network performance and find and solve network problems. If you plan to deploy network monitoring and control, ensure that the devices you want to manage support SNMP.


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