Sudden 'Unauthorised network' issues on Domain

[marsdenprimary]

Hi,

 

For some weird reason about four of our Win7 64-bit PC's have started failing to be able to contact our DHCP server. Just getting 'Unauthorised network' in the connection settings and can't change it from 'Public'

 

EDIT: IT NOW SAYS 'UNIDENTIFIED NETWORK' and the 'unauthorised' bit has gone... :-/

 

It's very strange as they were fine before. They are connected to a switch in a cab on the top floor which is fibred to another cab on the lower floor. This then connects via CAT 5e to our main switch.

 

Does anyone know what it could be? I have tried the following already:

 

- Removing the ethernet adaptor and reinstalling

- ipconfig /release and ip config /renew (when doing this it fails to renew, even though it gets an IP assigned on boot up)

- Removing from domain but then failing to be able to rejoin

 

Help appreciated as it's driving me nuts!

Edited April 15, 2013 by marsdenprimary

[sted]

anything else on that switch? might be worth dragging a known working laptop there disable wifi and see what it gets

[marsdenprimary]

anything else on that switch? might be worth dragging a known working laptop there disable wifi and see what it gets

 

Only other thing on there is a Unifi Wifi access point... I'll grab a laptop and give that a whirl and report back.

[marsdenprimary]

Okay well it did it with a laptop too... so at least it rules out the machines. I think i'd have preferred it to be the machines to be honest...

 

Any other ideas?

Edited April 15, 2013 by marsdenprimary

[EvLPhenom]

We have had this happen before. It has been something spamming the network.

 

We find that the quickest way to identify it is to plug in a laptop. Disable wifi then run ping from a command promt to a ip address (usually a server) with -t. It will then report back saying that it couldn't connect or something to that effect.

 

Remove patch cables until you get a successful ping back from the machine. Then just find where the patch corresponds to in the building.

 

We have had printers wifi aps and computers all cause this problem in the past.

 

Hope this helps

[3s-gtech]

Do you have rogue AP detection running elsewhere which has singled out this AP to attack it? Certain network infrastructure/APs enable this, by DDoS'ing the AP.

[marsdenprimary]

Do you have rogue AP detection running elsewhere which has singled out this AP to attack it? Certain network infrastructure/APs enable this, by DDoS'ing the AP.

 

Just had a check and we do...although this shouldn't really affect wired machines should it? Are you suggesting I unplug the AP?

[3s-gtech]

Perhaps - try it and see! Not massively confident on that one, but just wondering if that switch is getting flooded with traffic due to the AP being attacked.

[marsdenprimary]

Right then. The problem has gone... Turned out it was the fibre optic link between cabs!!! Turned off the converters, turned them back on again, problem solved. Flipping crazy problem thanks for your help peeps!!!

[marsdenprimary]

It's BACK but in a different form... :-( Seems now the connection on the machines is intermittent. I'm definitely suspicious about the fibre optic converter...any experience of this? Tips??

[Torrevez]

Any device can fail I guess, have you got another set of converters you can try? Have you had any building work done recently near the fibre run, maybe its been damaged.

[ConradJones]

my money is on dodgy fibre or transcievers,

 

swap what you can logically, its hard if you haven't got spares.

[ass17]

Fibre converters are pants! Use proper fiber SX or LX modules.

[marsdenprimary]

Any device can fail I guess, have you got another set of converters you can try? Have you had any building work done recently near the fibre run, maybe its been damaged.

 

We have had work done but i don't think it has been near the fibre link

[marsdenprimary]

my money is on dodgy fibre or transcievers,

 

swap what you can logically, its hard if you haven't got spares.

 

Yeah that's my first port of call i think- going to order a new tranciever and take it from there :/

[sted]

Yeah that's my first port of call i think- going to order a new tranciever and take it from there :/

 

at one of the schools i used to support i swear i went through fibre convertors so quick i can remember one period where i seemed to replace them weekly from the stock of spares dreadful things

[Torrevez]

Fibre converters are pants! Use proper fiber SX or LX modules.

 

I agree, we have just removed all our converters and installed the proper modules. File transfer times have more than halved

 

They are expensive compared with the cheap converters you can pick up, but well worth the money.

[marsdenprimary]

Well- ordered a new converter with no joy, the problem was still there. We asked our local networking company to come in and have a look to see if they could fix the problem. The tech guy came in, checked through all the same things I checked through like cables, connections, switching things off and on and it still didn't work. He left. Five minutes later- the computers suddenly began receiving IP addresses and connecting to the network no problem... A few days later- they stop working again and stop receiving IP addresses.

 

I put a new switch in the cab where the PC's are terminating...still no joy.

 

Anyone out there got any idea??!!

 

The only other solution i can think of is instead of the fibre connection, using CAT5e to link the problem cab to our main hub like all the other cabs.

[ass17]

Cat 5e or 6, either will do as I don't see you have many options left. Have you updated you switch firmware at both ends?

[marsdenprimary]

Cat 5e or 6, either will do as I don't see you have many options left. Have you updated you switch firmware at both ends?

 

They're unmanaged switches so I don't have the ability to do that... looks like there is only one option left!