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Old August 14th, 2011, 12:59 PM
andyclegg andyclegg is offline
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Default Problem with autonegotiation using GS116

Hello, I have got a problem related to auto-negotiation on a small wired network, where all devices (computers of different NIC capabilities, printer, router) are connected into a GS116 unmanaged switch. I've tried reading up on auto-negotiation, but nothing seems to cover these basic questions. I hope somebody on here can provide a bit of insight to help me diagnose the problem.

One of the computers now only works when manually configured to 10MBps Half Duplex. There is no network connection when it is set to auto-negotiate or at any other speed setting (though it used to, until a few weeks ago - not sure what changed). I've read that if manually configuring, half-duplex must be used. Rather than just accept this slow speed, I really would like it to work as fast as the various devices allow.

1) I assume that auto-negotiation is done for the whole network, rather than separately for each connection between device and switch.
2) Is auto-negotiation done regularly, or is it a one-time process ?
3) If its a one-time process, how do you instigate an auto-negotiation if say you unplug/change devices on the network ? Do you just power cycle the switch, and/or do you have to also unplug all network connections ?
4) If its a regular process, how frequently does it happen ? If I disconnected a slow/bad device, how long would it take for the network to change its speed.

Many thanks in advance,

Andy Clegg
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Old August 14th, 2011, 06:25 PM
fordem fordem is offline
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Default Re: Problem with autonegotiation using GS116

Auto-negotiation is handled on a "per port" basis with each port being able to support a different configuration as required to match the device connected to the port, and is done on a "per connection" basis - every time a device connected to a port, or if that device is powered off & back on.

If manually configuring, you really need to be able to configure both ends of the link which the GS116 will not allow you to do, so I would suggest leaving the configuration set to auto and letting it do it's thing - under normal circumstances this will work perhaps 99% of the time, and you will, very rarely, run into a situation where it doesn't work when connecting a new or different device, in which case you fiddle until you do get a working connection.

From the sound of it, you have a defective switch - open a case for it at my.netgear.com
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Old August 15th, 2011, 02:02 AM
andyclegg andyclegg is offline
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Default Re: Problem with autonegotiation using GS116

Fordem - excellent, I didn't realise that it was on a port-by-port basis. It does therefore sound like the switch may have gone defective (maybe on only one or two ports). I will try swapping the ports used, as some devices seem to work fine on auto-negotiate, whereas others won't, and maybe its just down to which port they are plugged in to.

Is there anything I should do to fully reset the GS116 , other than a simple power cycle ? I couldn't see a "reset" button on the case.

Many thanks,

Andy
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Old August 16th, 2011, 12:45 AM
andyclegg andyclegg is offline
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Default Re: Problem with autonegotiation using GS116

Looks like the GS116 is fine. When connecting the troublesome PC into a port on the GS116 that works fine with auto-negotiation on a different PC, it does exactly the same. No network for auto-negotiation, or any other speed/duplex setting, except 10Mbps Half-Duplex.

With auto-negotiation it looks like it is attempting to connect - I occasionally get the "Identifying ..." stage but quickly it reverts back to "Network cable unplugged". When manually set to 10Mbps Half-Duplex everything works fine (maybe I should just accept this )

So it looks like it is some subtle setting on NIC / operating system networking. Though I have checked most of these against the working PC. I will keep digging, and report here if I find anything. Thanks.
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Old August 16th, 2011, 04:15 AM
fordem fordem is offline
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Default Re: Problem with autonegotiation using GS116

You can - if you so choose - either replace the NIC (if it's an add-on card) or add a NIC (if it's LAN on motherboard).

Occasionally, in fact I would say very rarely, you may come across a particular NIC that is incompatible with a given switch, but this does not happen as frequently as it once did. A decade or so back I ran into the problem with a particular combination of 3Com cards, Cisco switches and a Windows/Netware combination.
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Old August 18th, 2011, 12:54 AM
andyclegg andyclegg is offline
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Default Re: Problem with autonegotiation using GS116

Hello Again, It is still not resolved, but I have done some testing to try to pinpoint my auto-negotiation problem. Here's what I think I have found out:

- with only two PCs into the GS116 (both auto-negotiate), the troublesome PC seems to give a semi-reliable connection at 100Mbps. The reason for saying "semi-reliable" is that pinging the other PC *occasionally* gives "host unreachable" or "general failure". This is with both PCs plugged directly into the switch with short LAN cables.

- with the troublesome PC connected via a hardwired socket (i.e. more cabling/connections) auto-negotiate does seem to pick up and largely maintain at 100Mbps connection though the ping failure rate seems to increase slightly (though admittedly that could be wishful thinking)

- with all devices (several PCs, a router, a printer) plugged into the switch the troublesome PC fails to establish a connection with auto-negotiate. Manually setting it to 100Mbps half-duplex seems to give the occasional good ping reply - but no way near enough for a reliable connection. Manually setting to 10Mbps half-duplex gives a very reliable (100%?) connection.

So I guess my next question is why would things degrade as you connect more devices into the switch ? Is it a loading thing ? Total cable length - perhaps combined with sub-standard cabling ? Could one of the other devices is bad causing the switch to misbehave - though they all have good network connectivity ?

Once again, many thanks for anybody who can shed some light. My knowledge of networking is slowly increasing.

Andy

BTW - troublesome PC is a laptop, so no chance of swapping/new NIC.
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