Collision LED On Hub - What Does It Mean?

  Blitzer 17:23 28 Jan 06


Having problems at work with our small network of computers, namely that we're experiencing irritating slow down particularly noticeable using Sage software. Went to work today to try and find the cause but with little success. Tried installing anti-virus s/w on two machines (6 in total + server) and Spybot but found nothing. Also performed Windows updates again with little effect.

However, I did notice that the collision LED on the hub at times with flickering on/off and I'm assuming this is showing a problem with the network itself rather than virus? Thing is I'm no network expert so don't actually know what the collision LED signifies - does it indicate a hardware or software problem for example or could it be either?

We have a BT broadband service/modem to which the server is directly connected. All other OC's on the network are also connected to the BB modem but go through a hub. I'm sure at one point all PC's and server were turned off, but the hub still had two LEDs suggesting two PC's/hardware were still running/active on the network is that correct?

Any suggestions as to what I can do to identify the cause of the collision LED being lit and more importantly why the network is slowing down so badly would be much appreciated. Thanks in advance. :)

  De Marcus™ 17:35 28 Jan 06

Packets received simultaneously on two or more ports will result in a collision and light this LED.

Sorry not much help, but at least you know why the collision led is flashing.

  Blitzer 17:52 28 Jan 06

Thanks. :)

Just been trying to find something on the web about it and found out pretty much the same. Does point to the slow-down as this being the problem but unfortunately does not give me any idea of what is causing the collision or more importantly how to go about sorting the problem. :(

Thanks for the help - it's a start. :)

Anyone else have any ideas of where/how to locate the fault?

  Blitzer 17:54 28 Jan 06

Or should I say it does point to the collision of data as being the cause of the slow-down. Anyone have any idea whether this is more likely to be a software or hardware problem? If hardware where to start looking? Same goes for software problems I guess LOL! :)

  mgmcc 19:31 28 Jan 06

>> I'm sure at one point all PC's and server were turned off, but the hub still had two LEDs suggesting two PC's/hardware were still running/active on the network is that correct?

If the PCs were shut down, but still receiving mains power, the motherboard could still be powered and a hub connected to its network adapter will display a lit LED.

When multiple computers are transferring data over the network, there will be collisions. The light indicates that this is happening and that the hub is dealing with the collisions to prevent data corruption. This shouldn't in itself be a problem.

Are you actually using a network "hub" or a "switch"? A "switch" is a more sophisticated device which sends network traffic to the PC it is intended for. A "hub" is a very basic device to connect PCs and all data is sent to every PC in the network. The PCs then have to select which packets are intended for them. A hub will therefore be a much less efficient way of transferring data over the network.

This doesn't of course explain why there should suddenly have been a slowdown in performance, unless you have increased the number of computers in the network.

  Blitzer 13:08 29 Jan 06


98% sure it is just a hub yes. No extra PC's have been added to the network and everything did seem fine running the network with all three running Sage. i.e. Sage was smooth as what I'd regard as normal. It was not until I noticed the collision LED was flashing that I started to notice a degraded perfomance when using Sage. I've also had problems trying to backup my files to the server (about 400mb) over the network since these problems have been going on.

I'm kinda assuming that for the collision LED to light now and then would be regarded as normal. Perhaps we're now just seeing an increase in collisions which is then leading to the slow-down?

Problem is I have no idea where or what I'm looking for as a possible cause of the collisions in the first place. Virus? Network setting(s) on one or more of the PC's? faulty network card? Faulty hub? I mean could it be the hub has developed a fault and is not dealing with collisions as it shouidl anymore? I really just don't know what to do or try next?

Thanks for the help - very much appreciated, it's all helping me to understand more about how the network/hub works.

  Blitzer 13:11 29 Jan 06

Sorry my first sentence not very clear...

There's a PC dedicated as a server. Then 6 other PC's on the Network. I had three PC's switched on, each with a copy of Sage running. No collisions evident and Sage running smoothly as it should. Not until another PC was turned on and collisions started that Sage started to slow-down.

  mgmcc 08:16 30 Jan 06

Is it possible to establish if it is that *particular* fourth PC that causes a problem or if adding any additional computer causes a slowdown?

Does all of the hardware in the network support data transfer at 100Mbps? If the hub itself only supports 10Mbps, then the entire network will be reduced to this speed.

  Blitzer 12:45 30 Jan 06


Thanks for the ongoing help. :)

Nothing about the network has changed. No hardware replaced (certainly not network related), no additional PC's have been introduced etc. As far as I'm aware no new/additional software has been introduced other than anti-virus (Norton 2006) on the two XP machine plus Windows updates performed on the XP and Windows 98 machines. Also ran Spybot on these machines and found nothing significant other than the usual "Hitbox" type entries for tracking your surfing habits. The problem of course was there before these were changed anyway.

Basically something seems to have happenend whether it's failing hardware, software now playing up for no apparent reason or malicious software I really cannot say.

Did try swapping the Hub for another one today, but again no difference - actually had to swap it back as the spare had a faulty port. Also tried bypassing the BB modem thinking that may be to blame but again no luck.

Sort of systematically trying each PC in turn until the problem appears I don't know what to do. Problem is this is not my job (just the only one who really know anything about PC's here) and it's causing grief. Time and disruption have now become a big factor. Just wish I was at least closer to determining what is the cause of the slow-down. I'm assuming its down to the collisions, but even then I don't know what level of collisions would be regarded as normal? I'm assuming on a network of this size that it would be occasional, not pretty much constant as it appears.

  osama ffx 06:08 15 Feb 06

Hi everyone

I have the same problem and it start suddenly, and when this problem start the internet will be very slow or stopped.

I try everything but nothing work the problem continue even when the computer is shutdown
Finely I decide to change the network adapter, then the problem disperse

After few days the problem starts with the gate way this time!

  Blitzer 17:50 15 Feb 06

osama ffx,

We had a IT specialist come in and take a look at our network and the associated problems. His opinion was that it's probably a virus on one of the older PC's that don't have virus protection. The thought being that the virus is causing extra traffic on the network and causing the Hub to become a bottle neck as it's only 10mbs. This has now been changed to a 100mbs switch (did this earlier) and first impressions is that network traffic is back to "normal" speeds.

The plan at some point is to replace the older PC's on the network, install anti-virus software on the server that will also cover the networked PC's.

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