A rchive Date
[ 22-10-2000 ]
Category
[ Information Technologies ]
sub-Categoy
[ Networking ]
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[http://www.zdnet.com/devhead/stories/articles/0,4413,1600661,00.html
Solve the Address Mess
Find out how IP management software automates the assigning and tracking of IP addresses on a large network.
By Steve Rigney, September 4, 1997
IP Address Management
Until recently, most administrators used pen and paper or a spreadsheet to keep track of all the IP addresses on their networks. As networks grew, changed, connected to the Internet, and became intranets, managing IP addresses became a task that required a lot of time and effort--sometimes even a full-time employee. Fortunately, some software developers were able to foresee this problem and develop a set of specialized IP management applications for large-scale corporate networks. In this roundup we look at three of the most popular and powerful IP management tools: Cisco Systems' Cisco DNS/DHCP Manager (CDDM), Isotro's NetID, and Quadritek's QIP.
These products provide you with the servers you need to assign and track IP addresses, and the tools to set up and manage the servers. Before discussing the benefits and drawbacks of each solution, we need to look at how these TCP/IP services work and why you need an IP manager to set them up and keep them running.
The DHCP Server
If you manage a small LAN with only a hundred devices or so, you can probably keep track of all your IP addresses with a simple spreadsheet or database. When you add or move a device, you simply pull up the spreadsheet and see what addresses are available. Unfortunately, it can become difficult to keep track of adds and moves among thousands of remote and local users distributed in various subnets stretched across an enterprise WAN. Duplicate IP addresses can result, causing devices with the same IP address to lock up. This problem becomes heightened in networks connected to the Internet, as each IP address has to be unique among the millions of devices registered on the Internet.
The other big problem is the number of addresses available for all of your devices. IP addresses are divided into three classes: A, B, and C. Each address consists of four octets, or sets of eight binary digits, separated by decimals. The first octet determines which class the IP address is in. For example, the first octet in a class A address is 1 to 127; class B includes 128 to 191, and class C is 192 to 223. Class A addresses use the last three octets to identify specific IP nodes, while class B addresses use the last two octets for this purpose, and class C addresses use the last octet. While there are only 126 class A addresses in the world, each of them can be used to create almost 17 million unique host addresses. There are more class B addresses available, but each can be used to create only 65,534 host addresses. And while class Cs are the most abundant, you can only use them to create 254 addressable nodes.
Obviously, it's almost impossible to get a class A address, and even class Bs are becoming scarce. Therefore, most networks connected to the Internet have to use multiple class C addresses or deal with the problem of too many devices and not enough addresses.
A process called the Dynamic Host Configuration Protocol (DHCP) is designed to solve these two problems. In the most basic terms, DHCP is a client/server application that automatically assigns or leases an IP address to a device when it connects to the network. The device, such as a network PC, runs a piece of software called the DHCP client that issues a request when you start up. The server receives the request and issues the client an IP address. You can configure the DHCP server to assign the device a permanent address, generally called a static address, or a temporary address for a specified time, usually called a leased address. In leasing an address, it's not necessary to have enough addresses for all of your clients, because chances are they will not all be turned on at the same time.
The DNS Server
If you have a photographic memory, you may be able to remember all of the 12 numbers that make up a typical IP address, but most of us can't. This is whereDomain Name System (DNS) servers can help you. A DNS server is a database that keeps track of your network devices' IP addresses and associated names. For example, you can use a DNS server to associate the address 204.49.54.7 with the name srigney.pcmagazine.com. While DNS servers make it easier for your users to find network hosts and other nodes, they are generally difficult to set up and maintain, requiring that you edit complicated configuration or zone files when you make a change.
Merging the Servers
All three products in this roundup come with DHCP and DNS servers, but it's how the products integrate the two types of servers that sets them apart. By themselves, DHCP and DNS can't communicate. DHCP assigns the addresses, and DNS assigns the names. If you make a change to the information on one server, you'll have to edit the other manually. For example, keeping your DNS server up to date necessitates editing the database manually each time the DHCP server allocates or changes an IP address. If you use the servers with the products here, all of your DHCP information is added automatically to your DNS servers and made available to other DHCP servers on the network. Depending on the package , this functionality is provided by standard zone transfers or a common database.
Isotro's NetID and Quadritek's QIP use either a Sybase or Oracle database to keep track of all the available IP addresses and other information, such as host (device) names and subnet masks. Both NetID and QIP update the database and any DHCP and DNS servers with real-time information, but they do it slightly differently. For example, when a change occurs, NetID's DHCP server sends information to the database and the database automatically updates the DNS server information. QIP's DHCP server sends out a dual message when a change occurs. One message is sent to the DNS server and the other to the database. Unlike with NetID, if the QIP database is down, the DNS server will still be updated by the DHCP server.
CDDM doesn't use a common database but relies on a utility that sends name and address changes from the DHCP server to the DNS server--a process called zone transfers.
QIP and NetID provide another useful feature called dynamic DHCP addressing, which allows the DHCP client software running on the PC to use its NetBIOS or machine name as a host name. For example, the DHCP client will send the name of the PC with a request for an IP address to the DHCP server, and the server will provide that PC with an IP address and host name and then update the DNS server with all of the information. This allows you to assign each of your devices on the network with a user-friendly host name that everyone can remember. This means, however, that you need to give your PCs and other devices descriptive and unique names. CDDM currently doesn't provide dynamic DHCP addressing, but like the other two products, it does work with automatic addressing, which automatically assigns a host name you designate to a device when it requests an IP address.
Finally, all the products let you keep your previous DNS and DHCP servers in some locations if you wish. You can import the information to the database periodically and export it to update your servers, but you won't get automatic updates.
The Tools
In our testing, we found that the biggest benefit of these products, besides the server integration, was the graphical front end that helps you install and manage the servers. The tools include utilities with an easy-to-use interface for setting up your servers and configuring other settings such as your address ranges, subnets, and lease pools and then automatically editing the complicated zone files the servers need.
To make the tasks even easier, NetID and QIP include templates that you can use to set up a type of device (such as a workstation or router) once and then use the templates for all subsequent additions. Although using the administrative utilities that allow you to perform these tasks is better than editing zone files, they still aren't simple or intuitive. CDDM runs only on Unix, but NetID and QIP provide Windows-based administration utilities. Of all three, NetID provides the best interface for moving around and making changes.
Both NetID and QIP allow you to create detailed reports showing all of your addresses and how they are being used. CDDM doesn't offer any more reporting capabilities than the average DHCP server, so you will have to navigate the utility manually to gather information.
Overall, these products are expensive and complicated to install and learn. If you have fewer than a hundred IP devices, they are probably not necessary. But if you manage a large and changing network, you'll wonder how you lived without them.
All three products ease the process of configuring and maintaining DNS and DHCP servers on a large network. But QIP stands out for its combination of features and ease of use.
QIP was the only product whose DNS and DHCP servers could run on both Microsoft Windows NT and various flavors of Unix. The Editors' Choice goes to the Unix version, since we found a few bugs in the Windows NT version. QIP claimed to have fixed those bugs as we went to press.
While the features of NetID and QIP are similar--dynamic DHCP addressing, automatic updating of DNS servers with DHCP-assigned IP addresses, easy configuration of subnets, excellent reporting--QIP's installation was significantly easier than NetID's. And QIP's Web interface lets you view multiple reports from a browser. Cisco DNS/DHCP Manager is a decent solution for medium-size networks but is not as feature-rich as the other two products, and the version we tested had problems with Windows 95 and NT DHCP clients.
BIND (Berkeley Internet Name Domain)
A popular public-domain DNS server package created for the BSD (Berkeley Software Distribution) version of Unix but currently available for almost every Unix flavor.
BootP (Boot Protocol)
A protocol used for assigning IP addresses to workstations on boot-up based on the address of each station's adapter card. BootP provides data such as the subnet mask, gateway address, and DNS server addresses.
CIDR (Classless Inter-Domain Routing)
A method for combining several class C networks into a larger address pool.
DDNS (Dynamic DNS)
An open standard for dynamically assigning a user-friendly name to a DHCP-supplied IP address. (See WINS.)
DHCP (Dynamic Host Configuration Protocol)
A client/server protocol for assigning static and temporary IP addresses, and in some cases names, to network devices. DHCP can reassign IP addresses to devices on the fly.
DHCP lease
The length of time a DHCP client can use an IP address. DHCP leases are assigned by the DHCP server software.
DNS (Domain Name System)
A distributed database that maps network devices' IP addresses to user-friendly names.
Host ID
The part of an IP address used to identify a device on the network.
IP address
A 32-bit number consisting of four octets (sets of eight binary digits) that specifies a network address and a host ID on a TCP/IP network.
Subnet
A portion of a larger network that shares part of that network's IP address.
Subnet mask
A 32-bit number that uses the same four-octet format as an IP address. Subnet masks provide a method of splitting a single class A, B, or C address into smaller subnets.
TFTP (Trivial File Transfer Protocol)
A scaled-down version of FTP that allows you to transfer files between two host computers. Unlike FTP, TFTP does not provide any authentication.
WINS (Windows Internet Naming Service)
Microsoft's proprietary method for mapping IP addresses to NetBIOS device names.
What if you don't have a large enterprise WAN that merits the purchase of a high-end IP management suite, but you still want some of the same features? Well, the solution may be right under your nose--or NOS (network operating system). The most popular NOSs, including Novell's IntranetWare and Microsoft Windows NT Workstation 4.0, provide powerful TCP/IP services for handling the needs of many small or medium-size networks. Each of these operating systems includes a DNS and DHCP server, a Web server, and a multiprotocol router. Unlike the products in the main roundup, the TCP/IP servers in IntranetWare and Windows NT don't provide dynamic DNS updating, communicate with a central database, or offer a lot of management tools, but you may not need those features.
Windows NT's DHCP server 4.0 includes a DHCP Manager that makes it easy to set up address pools to lease or assign addresses to your clients when they log on. Unlike the DHCP servers we tested, Windows NT's DHCP server doesn't work with the BootP protocol 100 percent, so you can't use a device's MAC address to assign an IP address.
The DNS server in Windows NT is also easy to install, and it adheres to all of the IETF (Internet Engineering Task Force) standards. Although the product does not provide automatic updates of DNS servers with DHCP information, it comes closer than Novell's DNS server by offering Windows Internet Naming Service (WINS). WINS uses a client/server technique to keep a database of PC NetBIOS names and their associated IP addresses. Like DHCP client dynamic updates, it allows you to add the name of the PC to its IP address in the WINS database. Unfortunately, WINS works only withWindows 3.x, Windows 95, and Windows NT clients and does not interact with the DNS server.
Novell's IP Services
Like all IntranetWare services, Novell's DHCP server runs as an NLM. But this means that the configuration interface is limited to character-based menus and is not very intuitive. The DHCP manager is difficult to maneuver and is limited in some of its features, such as the ability to exclude IP address ranges from being assigned dynamically to certain DHCP clients. Unlike Windows NT's DHCP server, however, Novell's DHCP server does work with BootP clients.
The IntranetWare DNS server is not much easier to configure than the DHCP server, but it works with any client device capable of performing DNS lookups. You configure the DNS server by using the NLM-based utility, Unicon. Unicon controls many server functions and provides several debugging and error notification options. You can update IntranetWare DNS servers by importing zone files from other DNS servers.
Although it doesn't come with a scalable database, support dynamic DHCP addressing, or provide the number of reports that NetID and QIP provide, Cisco Systems' Cisco DNS/DHCP Manager (CDDM) was the easiest of the three products tested to install and use, and it could be a solution for medium-size networks. Unfortunately, we found a serious flaw in the present version: CDDM's DHCP server is not 100 percent compatible with the DHCP client that comes with Microsoft Windows 95 and Windows NT. The Windows DHCP clients accepted the IP address but not the host name from Cisco's DHCP server. If you want CDDM to assign your network clients a DNS name automatically, you will have to use a DHCP client from another vendor, such as Frontier Technologies or FTP Software. Cisco claims to be working on a solution to this problem.
CDDM runs only under several flavors of Unix, but Cisco informed us that it will offer a new version of CDDM for Windows NT in the second quarter of 1997.
The CDDM package includes the Cisco Server Suite 1000 and the Domain Name Manager (DNM). The Server Suite consists of DNS, DHCP/BootP, Network Time Protocol (for syncing time between servers), and Trivial FTP servers, plus a graphical management utility. The Domain Name Manager is a graphical browser allowing you to manage the DNS information on your network: adding address pools, creating subnets, and making address changes.All the software pieces work together. For example, when the DHCP servers lease an IP address to a network device, they automatically update the DNS servers with information that includes the device's IP address.
CDDM retails at $6,000 for 5,000 nodes (or $20,000 for an unlimited-node license), making it one of the least expensive products in this roundup. Our favorite feature is its ease of installation. A detailed worksheet with sample data walks you through every installation step.
Although the CDDM DHCP server is able to lease IP addressesto the devices on the network successfully, it provides only automatic name addressing, not dynamic addressing. For example, for each subnet you can choose a host name for your available IP address in the DHCP pool, and CDDM will assign that name to the new devices as they connect. To keep names separate, CDDM adds a number to the end of each, such as host1, host2, and so on.
Cisco DNS/DHCP Manager 1.0. List price: Tested configuration, $6,000. Cisco Systems Inc., San Jose, CA; 800-553-6387, 408-526-4000; fax, 408-526-4100; www.cisco.com/dnsdhcp
CDDM's DHCPconfiguration utility lets you set up all of your parameters without having to type cryptic commands at the Unix console.
With a Windows-based management interface, easy-to-define templates, powerful DNS and DHCP servers, and a Web gateway, Isotro Network Management's NetID 2.1 includes everything you need to install and manage an enterprise intranet.
Unfortunately, all these features make for a very complicated installation and configuration routine. NetID currently runs on several flavors of Unix and requires an Oracle or Sybase database already installed on your network.
The NetID Admin Tool, DNS and DHCP servers, and Web Gateway are separate modules that make up the NetID Enterprise family. By the time you add all of these modules, the product costs $18,000 with a 5,000-node DHCP license.
NetID was the most difficult product to install and configure in this roundup. The first thing you must do is install an Oracle or Sybase database. Fortunately, Isotro will resell you a copy of Sybase. After installation, you have to add the NetID users manually and set up the required security. The final steps involve installing the Sybase Open Client and Admin tool on a Windows-based PC, and then the DNS and DHCP servers on your Unix hosts. Isotro claims to be working on a Windows NT version of the TCP/IP servers, which may be available by the time you read this.
NetID stores all of the DNS names and DHCP IP addresses in the database, which the two servers constantly monitor for updates. Both NetID and QIP provide dynamic DHCP addressing, which means that the DHCP client can use its machine name to update the host name in the DNS server.
The Admin Tool runs on Windows 3.x, Windows 95, and Windows NT 3.51/4.0 and performs all of the NetID configuration and management tasks. It's fairly intuitive and uses multiple windows to show you information on your network, subnets, hosts, and IP addresses. You can also create basic text-based reports that provide information on the currently available addresses, leased addresses, and your subnets.
NetID allows you to create templates for adding, deleting, and changing IP information and for subnets and static IP addresses. The Web Gateway is a useful tool for performing basic management tasks from a remote location via a browser. It runs as a Unix application that uses JavaScript to convert the database information into HTML format. You can't perform every function from a browser, but you can make basic changes such as adding, deleting, and updating hosts.
NetID 2.1. List price: Tested configuration, $18,000. Isotro Network Management Inc., Ottawa, ON; 800-476-8762, 613-722-1921; fax, 613-722-1997; www.isotro.com
NetIDmakes it easy to divide your address ranges into subnets.
Having its own runtime database, DNS and DHCP servers, and Web interface, along with all the management tools you need, QIP is an excellent IP-address management tool for medium- size and large networks. QIP 3.0, from Quadritek Systems, is the first product in this roundup whose servers run on Microsoft Windows NT. Like NetID, QIP offers a Windows-based administration utility and provides dynamic integration between its DNS and DHCP servers. Although the Windows NT version provides a sigh of relief for Unix novices, we did find some bugs in the program. Thus, we gave our Editors' Choice to the Unix version only.
Having most of the same tools and features as NetID, QIP is also a fairly expensive package. Pricing is on a sliding scale starting at $5 per address for up to 2,000 addresses, progressing to $2 per address when you have more than 250,000 addresses. The configuration we tested, for 5,000 addresses, is priced at $22,500.
When it comes to ease of installation, QIP falls between CDDM and NetID. Its installation utility automatically installs the bundled database, unless you have an existing Oracle or Sybase database you want to use, and installs the utilities for managing the DNS and DHCP servers. One welcome feature is the menu system that lists commands in the order you need to execute them. For example, you can't create a subnet range before a subnet group.
Like NetID, QIP relies on a database to keep track of all the IP address information on the network. Unlike what happens with NetID, however, QIP's DHCP serversends multiple changes to the DNS server at the same time it is updating the database. By making two copies of the data, QIP guarantees that the DHCP information will be saved, even if the DNS server and database fail.
The Windows NT version is easy to install, but we found in our testing that it was unable to release an IP lease from the database, even when we turned off the client PC and used the Windows 95 IP configuration utility to release the address manually. Fortunately, the Unix version didn't have the same problem, and Quadritek is working on a fix for the Windows NT version.
Like NetID, QIP offers a Web interface. It allows you not only to add, change, and delete hosts and addresses but also to view multiple reports from a browser. QIP uses CGI scripts to convert the database information to HTML. A nice twist to the QIP Web interface is its ability to view reports. You can view reports based on IP usage, host names, and even the MAC addresses of your client PCs. Unfortunately, the Web browser caches the reports, so when you request another and select Submit, you end up viewing the same one unless you turn off caching in your browser.
QIP 3.0. List price: Tested configuration, $22,500. Quadritek Systems Inc., Malvern, PA; 888-683-2254, 610-725-8535; fax, 610-725-8559; www.quadritek.com.
QIP'sWeb interface lets you add, delete, and make changes to your IP addresses and servers from a Web browser]
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