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Informational Commands
If the problem is more thorny than a configuration issue, it can be
useful to know the perspective of the problem workstation; that is,
what the workstation can see, what it cannot see, and the state of
various informational commands as run from that workstation. You can
use various informational commands, as listed in Table 11.1, to see
the workstation's perspective on the network (these commands apply for
both Windows 9x and NT).
CAPTION: Table 11.1 Informational Commands
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Command Description
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netstat -r Shows TCP/IP routing table.
netstat -a Shows all TCP/IP sockets in use (client and server).
arp -a Displays the MAC-to-IP address translation table.
ping hostname or address Checks basic IP connectivity with hostname or
address.
tracert hostname or address Traces the route that a packet takes from
the current workstation to hostname or address. Shows each router that
the packet goes through on its way to hostname or address.
nbtstat Checks the NetBIOS name table.
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All these commands (except nbtstat) are more or less lifted from UNIX;
see Hour 12, "UNIX Networking Basics," for examples of their use in
basic TCP/IP troubleshooting. Hour 18 provides some in-the-trenches
techniques.
net
You should also be familiar with the net command. Type
net | more
at the command prompt. This will show you the multitudinous net
commands you can run. These are mostly file and print related; some
relate to networking configuration in general, as well. Some of these
functions do not have a graphical equivalent, so set aside about a
half an hour when you'll be undisturbed to check 'em out.
Friendly, Mon, Real Friendly
Say what you like about any other part of Microsoft networking, but I
will defend the built-in statistic-gathering features to the death.
Far and away the most wonderful thing about Microsoft networking, the
statistic-gathering features in the server and client programs, along
with SysMon (the affectionate term for the System Monitor), enable you
as Joe User to see how you're doing in terms of performance at any
given time. This means you can quickly and easily profile a particular
server or network segment. This is something that used to take a
network expert and a $10,000 piece of equipment to do, yet Microsoft
has now enabled everyone to do it. (Did I mention that I like this
feature?)
In all seriousness, this really allows you to do some powerful
troubleshooting cheaply. Let's look at a quick example: Suppose we
have an application that's for some reason running very slowly for a
given person. Other folks are running the application just fine, but
our confidence level is pretty low concerning how alike each
workstation is. We discover that the user can log into someone else's
workstation and work just fine.
Somebody suggests that we nuke the user's hard drive and make it just
like a setup that works. This is greeted with stony silence by the
user, who happens to be a big shot in the company. Apparently, this is
not the path that we will take.
The user says that he runs like molasses, and he seems right from what
we can tell of other people's workstations. What's going on? Is it the
client or the server? Is this subjective slowness, or is there an
objective way of measuring this?
We could break out the $10,000 network analyzer to measure the network
throughput by attaching it to the network segment and capturing each
packet between the client and server and then doing the math of amount
captured divided by number of seconds to get the amount per second.
However, because network throughput is easy to measure with the
Windows 95 System Monitor, we install this to the user's workstation
and add the Microsoft Network client's Bytes Read/Second statistic to
our chart. Figure 11.8 shows a monitor session; it reveals that the
Microsoft file and print session is running reasonably fast:
625KB-991KB per second. You can't expect much faster than that on a
10Mbps Ethernet network. You can tell that the workstation is working
hard keeping up (look at the CPU utilization and free memory). Both
drop when this file transfer is happening. In this example, we would
see normal output like this when running the application on a
different server.
[11-08t.jpg]
Figure 11.8 A monitor session.
We keep the System Monitor minimized and run the problem application.
Yes indeed, it's slow. We're seeing wide-area speeds on a LAN
connection. Right away we know that there's truly a speed problem on
the network; it has nothing to do with his workstation.
Or does it? We have a different server that runs another department's
stuff, so we decide to do the same measurements on that server using
the same application. In this case, the measurements are more in line
with what we're seeing on other workstations on the LAN. It seems that
this particular server and this person's workstation are not happy
with each other. The five minutes we spent with the System Monitor
accomplished a couple of important things:
o This person is not imagining things; we have objective data to
prove it.
o We've discovered that the workstation can connect to a
different server without the slowdown problem; we now have a
workaround while we further diagnose the problem server or
workstation.
In this particular case, the server is definitely a problem. It's not
a Microsoft server; it's a UNIX server running an older version of an
SMB server. However, the server is talking to other PCs just fine.
Something about the age of the server and the client software on the
user's PC isn't jiving properly.
We (very carefully) reinstall the Microsoft file and print client to
the workstation, consistent with other workstations in the department;
then we reapply the Windows 95 Service Pack 1. In this case, because
we're dealing with a VIP, we make a backup of his hard drive-just in
case we cause more problems through this process. After the
application of the client and the service pack, we test again with the
System Monitor. The problem is gone, and the VIP is happy.
______________________________________________________________
We'll talk more about network throughput in Hour 22, "The Network
Is Slow!"
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