微软认证专家杂志的手持式网络分析仪应用介绍

微软认证专家杂志关注手持式网络分析仪以及哪种分析仪可以提供准确的网络预测

网络管理员可以拒绝使用陈旧的故障诊断技术或默认的诊断工具。随着网络测试仪市场的不断增长，针对不同的IT专业人员可以提供不同价位的产品。看看微软认证专家 James Carrion 是如何评论福禄克网络公司独有的解决方案。

微软认证专家：“OptiView 局域网分析仪让您拥有一双鸟的眼睛来查看整个网络的状况。NetTool 网络万用表在检测更高层上的问题方面有着卓越的能力——大多数工程师在没有笔记本电脑的情况进行故障诊断会出现困难。”

[原文摘抄]
It’s a moment every administrator dreads: Your network is crying for help, and you don’t know why. Wouldn’t it be great if, right in your hand, you had a tool that could diagnose the problem? We test four handheld analyzers to see just how they can make your job easier.

by James Carrion

July 2003 — When the network is down, screaming users and an irate boss turn some network administrators into troubleshooting machines. Others simply rely on the fates, with ad-hoc troubleshooting techniques or default diagnostic utilities. Worse yet, some put their faith in plain, dumb luck (i.e., reboot everything). Sure, the network eventually comes back up, but the extended downtime has your users and boss still fuming and, perhaps, even plotting your demise. What you really need are good troubleshooting tools that can quickly pinpoint the problem—and make everyone’s future a bit brighter.

Handheld network analyzers started out as basic, physical-layer, network-diagnostic tools and have evolved continuously. They now perform multifunction diagnostics at all layers of the OSI model, helping administrators troubleshoot myriad network problems. Ten years ago, I watched a co-worker use a multimeter to detect shorts in cables and connectors while lugging around a heavy oscilloscope to perform basic diagnostics. Today’s network analyzers—which are small, self-contained devices—can perform the same tests and provide results in a user-friendly graphical format.

 
High-Level Analysis

Fluke Networks’ OptiView Pro Gigabit Integrated Network Analyzer

To call this tool a handheld network analyzer is stretching things a bit, as it feels like you’re cradling a football. OptiView is a handheld tablet computer that comes with a PC card slot, USB and serial ports, and a touch-screen color display. OptiView is designed for LAN/WAN/wireless troubleshooting, and the standard model is configured with 10BaseT and 100-BaseTX interfaces. You can upgrade to one of the Pro models—which adds RMON2 and 100BaseFX fiber-optic interfaces, as well as packet capturing and decoding capabilities—or to the luxurious Pro Gigabit model, which offers a 1000BaseSX interface. The Pro Gigabit model tested had an optional 802.11b wireless diagnostic PC card.

OptiView troubleshoots problems at all seven layers of the OSI model, so it understands the basics of lower-level protocols (like Ethernet and IP) and is equally fluent in higher-level protocols, such as NetBIOS and Server Message Blocks (SMB). OptiView comes with two basic diagnostic programs: OptiView Analyzer, which diagnoses network problems on LAN ports, and OptiView Wireless Analyzer, which troubleshoots 802.11b wireless networks.

OptiView LAN analyzer gathers a large amount of diagnostic information—including LAN utilization, top protocols used, top talkers, top conversations and so on—to give you a bird’s-eye view of what’s happening on the network. The built-in discovery tool finds all network access devices, SNMP agents, hubs, switches and routers, IP and IPX networks, and NetBIOS hosts and domains, and reports any problems encountered. It has built-in ping, trace route and route-table viewer tools and comes with a separate Management Information Base (MIB) browser.

The built-in cable tester checks fiber and copper cables and graphically maps out wire pairs through a built-in or remote wiremapper. Another neat feature is the traffic generator, which places real traffic loads on the network. A built-in sniffer can capture and decode network traffic.

 
Figure 1. Fluke's OptiView troubleshoots problems at all seven layers of the OSI model.

I put OptiView to work by troubleshooting my own test wireless network. It immediately detected my SMC Networks access point, secured an IP address and warned me that Wired Equivalent Privacy (WEP) wasn’t enabled, so packets were being transmitted in the clear. I was able to capture all the wireless traffic between my laptop and the access point and decode the packets. In truth, I’m not too worried about the lack of security because I live out in the boondocks; unless the deer are war driving, I’m pretty safe.

Overall, the Optiview Analyzer is a great, albeit pricey, product capable of troubleshooting almost any network problem that a large enterprise network could experience. There were a couple of negatives: The color screen was hard to view, and the operating system was out of date years ago. I would hope that Fluke upgrades to Windows XP or Windows 2000, as Windows 98 is antiquated for such a device.

Small but Mighty

Fluke Networks’ NetTool Inline Network Tester

NetTool is about the size of a handheld video game and can be used to test basic network connectivity or discover devices and protocols on the network and report network problems just like its big brother, Fluke OptiView. It has two RJ45 jacks into which you can plug both ends of a patch or crossover cable to test cable length and wiremap. You can also plug it inline between a hub and a computer connection; NetTool will report LAN speed, discovered protocols, discovered devices (routers, NetWare or NetBIOS servers, printers, and so on) and network utilization. There’s also a built-in ping tool.

NetTool comes with a software package called NetTool Blaster, downloads firmware updates to NetTool’s serial port and uploads screen captures in .BMP format. You can also customize NetTool’s splash screen with your own name and graphic.

 
Figure 2. Fluke's NetTool can be used to test basic network connectivity or to discover devices and protocols on the network.

Putting it to work on my own test network, the NetTool quickly detected my test servers and verified name resolution was working. Using the Optiview Analyzer to inject a traffic load on the network, the NetTool correctly reported the network utilization rate.

As a basic layer 1 to 3 troubleshooting device, NetTool does an adequate job, and field techs will benefit from its portable size. It really shines in its ability to detect problems at higher layers—something most in-the-trenches technicians would have problems diagnosing without a laptop computer.

If a computer can’t access the network, you can quickly eliminate the source of the problem by verifying Layer 1 and 2 connectivity. This could be done by plugging in a laptop to the same network jack and using the standard Ping command, or you could use the cheaper, more portable Pinger instead.

The Future Is in Your Hands
Troubleshooting a network requires skill and patience, but you can fix any problem quickly with the right tools. On the high end, the Fluke OptiView offers all the diagnostic tools you need to find out what’s ailing your LAN/WAN or wireless network. The Fluke NetTool don’t offer the bells and whistles of the higher-end tools, but they do offer enough features for you to narrow down most physical and network layer problems. Most important, these tools will keep your network humming, your users happy, and make your job easier. 

James Carrion, MCSE, MCT, MCNE, CNI, has worked as a computer consultant and technical instructor for the past 14 years. He’s the owner of and principal instructor for MountainView Systems, LLC, which specializes in accelerated MCSE training. You can contact James about "Palm Reading" at jcarrion@mntview.com.