General Network Troubleshooting 3

[Genimuse]

I'm trying to help a small non-profit medical clinic with their in-house network. They have constant problems with a couple of machines transferring data very slowly, some machines occasionally not being able to see other machines, etc.

The setup is pretty simple: two buildings with a switch on each side. From the switch most connections are directly to machines, though there is one hub on one side to expand it out to a few other computers. Almost all NICs are at 10Mbs, though a few are at 100Mbps (though from the hub they're all 10s).

Anyway, I don't know much about networking, unfortunately -- just very basic stuff -- and so I was wondering if:

1. You can suggest a basic networking tutorial/overview somewhere on the web that will give me some idea of what to look out for, and

2. If you know of any free (the clinic can't pay) network troubleshooting software that might be able to point to problems for me, be it collisions or a bad machine or what have you.

Any thoughts? Thanks in advance.

 

[netmanrick]

You might want to start with a book or 2 first to get a basic understanding of what is going on in a networked environment.
Look for a book entitled Upgrading and Troubleshooting Networks.
You have some tools built in to the OS and equipment: Ping,
nbtstat,tracert,etc.

Rick Harris
SC Dept of Motor Vehicles
Network Operations

 

[bobmpalmer]

You could also check this out

http://dast.nlanr.net/Projects/Iperf/#download

Bob Palmer

http://www.resisystems.co.uk

The most common solution is H2O!

 

[Genimuse]

Thanks very much to both of you!

 

[Parcival21]

IF some of the PC's have problems you could start your troubleshooting with checking the duplex and speed setting on both NIC and Switchport. They should both be the same.
bye, busche

 

[vipergg]

As previous poster said this sounds like a speed/duplex issue on the client pc's . Depending on what type of switches they are using ,managed or unmanaged you would have to look at the switch ports to see what they are set at if it is a managed switch . If it is a umanaged switch then all pc nics should be set at auto . Basically the client pc nic settings much match what is on the other side on the switch .

 

[Genimuse]

I've been doing some looking into it, and it appears that the switches are all auto-negotiating for speed and full- or half-duplex, as, it appears, are all the cards, and all seem to be set to auto-negotiate.

Yet on the most troubled computer, I discovered that outgoing data is incredibly fast sending data and incredibly slow receiving it (copied a 3Mb file to another computer, took a few seconds, copied it back, took several minutes). This, as I understand it, is a traditional sign of a duplex problem.

If everything on the network supports full duplex, would there be a problem with me setting everything to it?

 

[jimbopalmer]

Sadly, you can only usefully set full duplex on BOTH ends of each wire, so unless you can force your switches off auto-negotiate, you cannot set the computers to full. You may find that setting just the problem computer to half duplex solves your issue.

I wrote a FAQ on this in this forum.

I tried to remain child-like, all I acheived was childish.

 

[Genimuse]

I appreciate all of the great thoughts on this topic. Unfortunately I'm still stuck.

Let me describe the network and see if it provides any insights.

Switch A has 7 computers connected, all of which have 100Mbs NICs and all of which are on auto-negotiate. Switch A is on auto-negotiate.

Switch A is connected to Switch B, where there are 5 computers connected (all 100Mbs NICs and all auto-negotiate). Two hubs are also connected to Switch B, each of which has 3 or 4 computers connected, again all with 100Mbs NICs and auto-negotiate (if I understand correctly, this puts those computers at half-duplex, right?).

One of the hubs over on Switch B has a DSL modem connected to it (I'd prefer to move the modem to the switch but it's physically infeasible).

One computer on Switch A is having problems -- its send speed is fast but its receive is incredibly slow. This would, as I now understand, indicated a duplex problem. On that computer I have replaced the NIC, replaced the cable, plugged the cable into a different port on Switch A, etc., with no change. It most definitely is set to auto-configure, but manually setting it to half-duplex 100Mbs or half-duplex 10Mbs makes no difference, the problem remains. Because I'm using entirely different drivers with the new NIC, I believe I can assume that it's not them, either.

Here's the weird part, and maybe it will shed some light: two of the computers on Switch A (same switch as the problem computer) can see the problem computer but cannot connect to it. Every other computer in the place -- including others on that switch -- can see it and connect to it just fine. This is a new problem (the slowness in the problem computer is an old problem).

Multiple reboots of all computers and the switch make no difference, so I don't think I'm just having unlucky boots (as described on a duplex troubleshooting guide I read).

I'm sorry to have described so much. If this wasn't a little non-profit medical clinic with no real budget, I'd hire a network guy who knows what he's doing instead of bugging you guys with questions.

Any more thoughts?

PS: Is an OS reinstall on the trouble computer pointless?

 

[Parcival21]

Well the next point would be to check if there are errors occuring on the switch interface (for example collisions). Someone here might be able to tell you where to get a monitoring tool cause I don't know it. If there are no errors check the traffic. Maybe the computer is sending data all the time although you don't want the computer to send data (virus, trojan??). Because of the computer using half duplex it will have a lot of problems receiving data while sending data all the time. There might be collisions again...
bye, busche

 

[magistertc]

I have seen this problem when the cable connections are not perfect - just good enough to negotiate, but too many errors in transmitting data packets. Check your connections, jacks and plugs. If possible, move the computer to a different (working) location to test it.

 

[Genimuse]

On Friday I moved the computer to a different location on the network and it exhibited the same problems (though it was different computers that couldn't see it now). This narrowed it down to the computer itself (wish I'd done that before), since I'd already changed NIC cards and drivers.

So I wiped it, reinstalled the OS, and poof, the problem is solved. Up and down speeds are both super-fast, and the whole network can see the computer.

Thanks everyone for their help.

 

[Castor66]

If this happens again - blame the user for installing some form of spyware/virus. If a system is installed by you and works acceptably for a period of time it is almost invariably some form of rubbish installed. It happens to us all the time and I find all sorts of stuff installed. 1 person had 2000+ items found by SpyBot! No wonder they complained of performance.