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Network troubleshooting with Fluke’s NetTool Small networks involving just a few PCs are easy to troubleshoot but it’s a different story with larger networks. Fluke’s NetTool is a snack to drive and it works like magic when it comes to tracing network problems. By GREG SWAIN There’s usually not a lot that can go wrong on a small computer network. After all, it either works or it doesn’t. And if it doesn’t, the problem can be quickly diagnosed without specialised test gear. That’s because small networks are really quite simple in concept. Generally, they consist of just a few computers hanging off a single hub or perhaps several hubs linked together. If you strike problems, it’s no big deal 26  Silicon Chip to check each machine for correct setup; ie, checking the installed protocols and checking that other settings, such as TCP/IP addresses, subnet masks and workgroup names, are correct. If you suspect a hardware fault, then a PC itself makes a pretty good piece of diagnostic gear. It can indicate whether or not its network interface card (NIC) is properly installed and it can be used to run diagnostic software. For example, if you are using the TCP/ IP protocol, you can try pinging other computers on the network to see if you get a response (see panel). Another diagnostic tool, Net Watch­ er, lets you view your shared resources and check who is accessing these resources. However, it cannot perform traffic analysis or indicate potential problems. Often, hardware faults are diagnosed by swapping suspect components until the problem goes away. On a small network, it’s really just a matter of using your common sense, plus a bit of trial and error. Large networks When we move to large networks, the trial and error ap­proach is just too time-consuming. There are just too many fault possibilities and other complications to make this approach practical. On a large network, you’ve probably got a DHCP server (for dynamically assigning TCP/IP addresses), primary and secondary WINS servers, a PDC (primary domain controller), a BDC (backup domain controller); SMTP and POP3 mail servers; and perhaps a DNS (domain name server). No; I’m not going to explain what all these services do. This stuff is for the professionals and if you don’t know, you probably don’t need Fluke’s NetTool. Suffice to say, there are lots of things that can go wrong on a large network. How do you know if the DHCP server has lost its marbles and started issuing duplicate IP numbers? Or if there’s a rogue protocol on one or more machines that’s gumming up the works? Or if there are lots of data collisions slowing things down? Or if the WINS server is out to lunch or signal levels are too low? To run these problems to ground, you need a serious network analysis tool such as Fluke’s NetTool. It works with 10Base-T and 100Base-TX networks and can quickly identify a wide range of problems. But its talents don’t end there – hook it into a network and it will eventually identify the major components and services on that network (it also detects Token-Ring networks and phone systems but cannot analyse them). The Fluke NetTool As you’ve probably gathered by now, NetTool is aimed at professional network administrators and installers. It’s a hand­held device that combines cable, network and PC configuration testing into a single unit that’s incredibly easy to drive. The exterior appearance of the NetTool is disarmingly sim­ ple. It has a large LCD screen that displays data in alphanumeric and graphical form; two RJ-45 sockets for accepting network cables; four tricolour LEDs; and six pushbutton switches. These switch­es include an On/Off switch (green); four Navigation but­tons arranged in an oval (up, down, left & right); and a Select button. The tricolour LED indicators (two on either side) show the link and network “health” indication at a glance. For example, the Link/CLSN/ERR LED glows green when link pulses are present, yellow when collisions are occurring and red when errors Fig.1: plug a network cable into both sockets and NetTool shows the cable length and the “wiremap”. Fig.4: the “wiremap” adapter is useful for sorting out cables in a patch cupboard. Fig.2: the cable length can also be quickly determined in single-ended node. Note the “spool” icon. Fig.5: NetTool identifies both straight-through and crossover cables. are occurring. Similarly, the UTIL (utilisation) LED is green when utilisation levels are below 40%, yellow for levels between 40% and 70% and red for levels greater than 70%. The easiest way to operate the device is to hold it in one hand and activate the pushbuttons with your thumb. You turn the unit on or off by holding down the green Power button for two seconds. Cable testing First the simple stuff. Naturally, the NetTool can be used for cable testing. To do this, you simply plug both ends of the cable into the RJ-45 jacks on either side, power up the unit and press Select when AutoTest Flashes on the screen. When you do this, the unit checks both sockets in turn and then displays the results on the LCD in graphical form – see Fig.1. The length of the cable is also shown. This is great for identifying both “straight-through” and “crossover” cables and for quickly determining cable length. It can also quickly in- Fig.3: selecting the spool icon in Fig.2 brings up this display which shows the cable status. Checking Network Cables dicate a faulty cable; eg, if one of the connections is open circuit. A variation on this theme is to use the unit in so-called “Single-Ended Mode”, whereby you plug the cable into only one socket. Again, the unit will quickly determine the length of the cable (Fig.2), after which the cable status can be displayed by navigating to the Spool icon (top, right of the LCD) and press­ing Select – see Fig.3. In this instance, the four twisted pairs are open at 4.9 metres, which is the length of the cable being tested. The single-ended mode is also useful for identifying net­work cable drops. A typical scenario is where you need to identi­fy which cable in a patch cupboard connects back to a given wall socket. This involves plugging the NetTool into the wall socket and testing each cable in the patch cupboard in turn by fitting it with the supplied “wiremap” adapter (basically, a loopback device). When the correct cable is found, the wiremap adapter symbol appears on the LCD (Fig.4). It can then be selected using the navigation buttons, and the The “wiremap” adapter is basically a loopback device that’s used to terminate a cable (via a supplied coupler) or a wall socket. It’s used mainly for cable identification. SEPTEMBER 2000  27 Services, Problems And Health or metres, enable or disable the Auto power-off feature, adjust the display contrast and program in Unwanted Protocols. Unwanted protocols Fig.6: plug the NetTool into a network and it quickly identifies what’s on either end of the cable. It also shows link speed, signal polarity, signal level and the cable connections. Fig.7: selecting the NetTool icon itself brings up the NetTool setup display. This lets you choose the units of measure, adjust the display contrast and enable the auto power-off feature. Fig.8: the Unwanted Proto­cols screen lets you program the NetTool to watch for unwanted protocols on a network. We’ve selected NetBEUI here as a demonstration. Fig.9: the Problem Log lists any network problems that are identified. Fig.10: NetTool is able to identify all protocols that are present on a network. Fig.11: the IP entry can be probed to show the IP protocols that are present. Fig.12: the Key Devices entry shows all the servers, routers and printers that NetTool has found on the network. Fig.13: once it’s found key devices, NetTool can identify their IP addresses and indicate the services offered (eg, POP3). Fig.14: probing the Health entry brings up this display. The two meters indicate the network “health” on either side of the NetTool. Select button pressed to display the internal connections – Fig.5. Service identification This is where NetTool really shines. Plug it into your network, select AutoTest and it immediately determines what’s on the other end of the cable (usually a network hub). Altern­ative­ ly, you can connect the NetTool in “Inline Mode”. This simply involves connecting it between two devices simultaneously, such as a PC and a hub – see Fig.6. This mode is particularly handy for verifying that a PC is communicating properly with a network, for example. Initially, NetTool displays the advertised speed, duplex capability and link configuration. It then eavesdrops on the PC-to-network traffic as the PC attempts to access network resources, after which it shows how the PC is configured and lists any servers, routers or printers used. 28  Silicon Chip As shown in Fig.6, the LCD shows icons at the top for devices and below it a main Menu listing Problems, Protocols, Key Devices and Health. In addition, there are several indicators near the devices that show the link and cabling information, including link speed (eg, 10MB/s or 100MB/s), polarity, signal level, whether the cables are straight-through or swapped, and the duplex setting for each device (whether full or half duplex). This information is all there, at your fingertips, in a matter of moments. So, for example, if you’ve got a dodgy connec­tion, or if signal levels are too low, or if you cannot access a DHCP or email server, you can quickly diagnose the problem. Selecting an icon takes you through menus that are relevant to that particular device. Choosing the NetTool icon, for exam­ple, brings up the NetTool Setup display (Fig.7). Here, you can choose to display cable lengths in feet Fig.8 shows the Unwanted Protocols selection screen. As an exercise, we programmed in NetBEUI as an unwanted protocol and then connected NetTool to our own network which does in fact have NetBEUI installed as a protocol (along with TCP/IP). Sure enough, NetTool immediately flagged a problem at the main menu, by dis­ playing “(1)” after the Problems entry. Each of the menu entries can be selected, to take you through the various “Discovery” screens. Selecting “Problems (1)”, for example, brings up the Problems Log screen (Fig.9). In this case, the unwanted NetBEUI protocol has been correctly identified. OK, that’s a fairly simple example. There are lots of other problems that NetTool can identify and these are broadly broken down into Link Connectivity problems, Health problems, Netware problems (eg, frame mismatches), TCP/IP problems, DHCP problems, Name Resolution problems (eg, DNS server not found or PC DNS server incorrect), NetBIOS problems, Web and Email problems, and Printer problems. If it can’t find the Primary Domain Controller or Backup Domain Controller, NetTool will tell you. If the DHCP server is issuing duplicate IP addresses, NetTool will tell you. If there’s a duplex or speed mismatch, or an unwanted protocol or a du­plicate NetBIOS name, NetTool will show you. If you cannot con­nect to a DNS server, a WINS server or a mail server, NetTool will tell you that too. Protocols and devices Selecting Protocols naturally shows the protocols present on the network and these can then be further probed to show which services are present – see Figs.10 & 11. This feature, together with the ability of the unit to flag unwanted protocols, is handy if you are migrating a network away from certain protocols and want to clear out any old remnants. The Key Devices entry is particularly interesting. This lets you check out all the servers, routers and printers that NetTool has found on the network (Fig.12). In particular, NetTool can identify HTTP, SMTP, POP3, WINS, DHCP, DNS and Netware servers, as well as a router gateway. And if that’s not enough, it can identify the IP address of each one, determine its MAC address and (usually after a while) determine the NetBIOS name as well (Fig.13). By the way, NetTool doesn’t immediately identify all the services on a network when it’s first turned on. Instead, it has to “see” a certain amount of traffic on a network or device before it can supply protocol or health information, or even identify key devices. In that sense, NetTool can be considered as a passive device that sits back and listens to network traffic. It doesn’t actively probe for devices as such. The final entry in the main menu is Health and this brings up a graphical interface showing two meters. Here, you check each side of the link for healthy frames in real time. You can also use the Navigation and Select buttons to change the meters to show utilisation, broadcast traffic, collisions or error levels from either device to which NetTool is connected (Fig.14). PC configuration Troubleshooting an individual PC on a network involves connecting the NetTool between it and the hub and selecting the PC icon. You can then use NetTool to determine the PC’s configu­ration and network health by navigating through the various menus. In particular, the health screen is quite different to before (see Fig.15) and, among other things, indicates short frames, “jabbers” and collisions. Jabbers, by the way, are frames that are longer than the maximum legal The unwanted network protocols feature is handy if you’re migrating a network from one protocol to another or if you just want to find a protocol that might be causing problems. Basic Network Troubleshooting Utilities WANT TO SEE what’s happening on a network? The Net Watch­er utility (Win95/98) lets you view your shared resources and check who is acessing those resources. You’ll find it under the System Tools entry in the Start menu. If it’s not there, you will have to install it using the Add/Remove Programs wizard in Control Panel. YOU CAN quickly check the IP address assigned to a computer (and obtain other useful information) using the Winipcfg utility. It’s started by clicking Start, Run and typing winipcfg in the Open field and clicking OK (NT users should type ipconfig at the DOS prompt). This utility is particularly handy for checking that a PC is correctly obtaining an IP address from a DHCP server, either on a local area network (LAN) or via a dial-up (eg, Internet) connection. Also shown is the address of the DHCP server, the IP address lease period, the subnet mask and default gateway, DNS and WINS server addresses. THE “PING” UTILITY is installed with Win95/98, NT & Windows 2000 and is handy for verifying TCP/IP connections. It’s run from the DOS prompt by typing ping [IP address] or ping [host name], (eg, ping 192.168.0.100 or ping Starbug). The utility sends a series of data packets to the remote computer, listens for a reply and displays the results (see above). If pinging the IP address gives a response but pinging the host name doesn’t, then you may have a name resolution problem (check that the host name matches the entry in the local lmhosts or hosts file). You can also ping your computer’s own IP address (eg, to verify that its TCP/IP installation is working correctly) and use the utility to verify correct entries for default gateways, etc. SEPTEMBER 2000  29 LE ($121.00); and an AC adapter ($51.70). Power for the unit is normally supplied by four AA 1.5V batteries but for heavy-duty use, the NiHM recharge­ ables are the way to go. PC Configuration Conclusion Fig.15: typical health display for an individual PC on a network. It indicates short frames, jabbers & collisions (see text). Fig.16: the link configurat­ ion display shows the signal level and polarity, as well as the link speed and the receive pair. Fig.17: the IP and MAC addresses of the PC are shown, along with its NetBIOS name. This saves checking at the PC itself. size. Just thought that you’d like to know that, so you can sleep tonight! There’s also a new menu item called “Link Configuration” (Fig.16). As before, NetTool tells you the installed network protocols, the PC’s IP and MAC addresses (Fig.17), Netware frame numbers and its NetBIOS name and flags any network problems. Selecting the hub icon brings up a similar selection of menus. A handy feature here is that you can view the network segment ID. We won’t go into all the features here. By now, you should have well and truly got the message – this is a very comprehen­sive and versatile network analysis tool. all, as Fluke’s manual states, “What would we do without a little software in our lives?” Fluke calls the software “NetTool Blaster”. Among other things, it lets you update the internal “smarts” of your NetTool with the latest software (available from Fluke’s website) – see Fig.19. Also included on the CD-ROM are copies of the Quick Reference Guide and NetTool User’s Manual, both in Adobe pdf format. The manuals are easy to follow and the full version even includes a troubleshooting guide. This gives a concise explana­tion of each problem that can be detected by the NetTool and suggests possible remedies. Updating NetTool Optional extras Included with the NetTool is the wiremap adapter, a serial cable adapt­ er, an RJ45-to-RJ45 coupler, a Quick Reference Guide and a CD-ROM. After Naturally, there are a few optional extras available for the NetTool. These include a rechargeable NiMH battery pack ($30.80); a battery charger They say that good things come in small packages and that’s certainly true of the NetTool. It mightn’t look all that impres­sive at first glance but its simple exterior hides some very clever circuitry and software. And as we said at the start, it works like magic. Unfortunately, magic doesn’t come cheap. At $3184.50 (incl. GST) for the NT-IL (NetTool Inline) model review­ ed here, this tool is clearly aimed at professionals. However, if networks are your life (or perhaps the bane of your life), that figure could well be a bargain. It should be in every professional net­work­er’s toolbox. Alternatively, you can buy the NetTool Standard (NT) model for $1864.50. This model provides single-ended testing only but comes with a 50-use trial of the Inline Option. A software upgrade lets you turn an NT model into an NT-IL. Want to find out more on the NetTool? Point your web browser to www. fluke­n etworks.com/nettool; email sales<at>fluke.com.au; or phone Fluke on (02) 8850 3333. You can buy the Fluke NetTool from Fluke, Namlea Data Systems (phone 1300 303 069) or from Anixter AusSC tralia (phone 02 9333 0800). What Would Life Be Without Some Software? Fig.19 (below): pressing the Update NetTool button shown in Fig.18 brings up this dialog box. You can then reprogram your NetTool with the latest software revision. Fig.18: the NetTool Blaster software lets you update to the latest software revision and even download screen shots on the NetTool to your PC (that’s how we got the screen shots in this article). 30  Silicon Chip Above: the NetTool is supplied with a CDROM, a serial cable adapter (for connecting it to a PC), a wiremap adapter, an RJ45-toRJ45 coupler and a Quick Reference Guide. A few optional extras are also available, including an AC adapter, a rechargeable NiMH battery pack and a battery charger.