"Interesting" situation in a classroom

[edcirh]

The network connection in one of my classrooms dropped several weeks back. As the classroom was barely used, it wasn't a high priority.

 

Anyway, doing the diagnostics pointed to the wall socket being faulty. That's now been resolved but I've still got no network connection in the room.

 

I've bunged a LAN tester on (nothing fancy, just continuity/wire order) and it shows that the cabling is fine from the plug going into the back of the PC all the way up to the plug going into the switch (i.e. all wires in the cabling connected & in the correct order). The network is Cat5e (& I use 568B wiring order everywhere if that makes a difference).

 

I've tried 4 different ports on 2 different switches, 2 different PCs, & new cables on either side of the run from classroom to switch, but still get no joy. No life on the NIC LEDs or the switch LEDs. Nothing. Nada. Nix. Zilch. Not a sausage.

 

Any ideas?

Ian

[jamesreedersmith]

cable length?

[edcirh]

From the PC to the wall socket c.14m (I know, I know, but teachers will insist on moving things around!), and from the Wall socket to the switch c.34m...

[FN-GM]

Is there a connection at all?

 

Have you tried with another computer?

[edcirh]

Even if you got your wiring order wrong, it would still show a connection, but with data errors.

 

The cable length is well under the limit.

 

How odd.

 

Has anything changed recently? New lights, fans, electrical gubbins?

 

Back in the day when i used to cable, a common problem was the cables not in their proper pairing. They'd pass the continuity test, but the switch ports would show loads of errors as the cables would pick up all sorts of noise. But if you're sure that they're paired properly, this can't be it.

 

Nope. There's been a fair bit of work in there just recently, but a) nothing electrical/electronic & b) nothing before the network connection initally went down & we had the wall box replaced.

 

Is there a connection at all?

 

Have you tried with another computer?

 

Yep, no connection at all.

 

I've even checked that the NICs haven't randomly become disabled (which has happened to me before!) but they're quite happy, just sat there, smugly displaying "network cable unplugged". I wonder if the County Network team have performed their ritual sacrifices to the Networking Gods this month...

[FN-GM]

Did you try another computer?

[edcirh]

What about the ethernet protocols... maybe auto-sense & auto-negotiate has gone south.

 

Are the switches set to auto? Try setting them to a fixed setting: 100Meg Full duplex on the switch side, see if the NICs pick that up.

 

Hmm, that's a thought - I'll try bouncing the switch before anyone gets in tomorrow just in case the auto-sense/auto-negotiate have got their knickers in a twist - I'd not really given much thought to the switch, working on the basis that it was new in in February and every other port was working fine. Not convinced that the reboot will fix things, though, because I've patched the room into the other switch in that cabinet & still get no connection.

 

Still, stranger things have happened...

 

Did you try another computer?

 

Sorry, I should have said Yep I have, & I'm still getting no connection...

[laserblazer]

I had a similar problem and it turned out to be the patch lead from the panel to the switch.

[edcirh]

Also, see if any kids have got into the switch - I assume it's managed.

Maybe they've switched off all the ports!!!!!

 

Rule 1: Never assume ANYTHING!

 

The cabinet is right above a teacher's desk - one of our stricter/most respected teachers - so I've no worries about pupils getting to it. The switches are "limited managed", whatever that means (my guess is cheap!)...

I had a similar problem and it turned out to be the patch lead from the panel to the switch.

 

I've tried different patch cables as well...

 

[edcirh]

What I meant was is there any way they could telnet into it, or do the switches have a web front end? If the passwords aren't set up, they can be remotely configured (and ports switched off).

 

nope, our kids couldn't spell telnet, let alone use it! The admin passwords were set by County when the switches were installed, there aren't any shortcuts to the admin web interface anywhere, & we've not got any pupils that are that up with IT that they'd realise there was a web interface to some networking devices...

 

Have you power cycled the switch(s)?

 

That's Plan A for tomorrow morning...

[p858snake]

Tried a different switch? would rule out/in cabling issues.

[Ric_]

Have you tried re-terminating the run at both ends?

 

I found a point the other day that some muppet a forced the socket through on which caused the pins not to connect correctly. After re-assembling the point it worked fine.

[tommccann]

i had a similar problem once and it turned out to be a cross over not straight through cable (or the other way round can never remember which)

[K.C.Leblanc]

Given the senario I'd start by testing the connection with another PC.

 

Have you double checked the wiring. I spend ages on a problem here, the previous tech had made the same wiring mistake on both ends of a connection (he'd put the 4 pairs next to each other instead of placing one middle pair inside the other), it tested fine on a dumb tester but wouldn't carry any data.

 

If the PC is ancient try forcing the switch down to 100m/b.