Peculiar Pin Layout 4

[IanGlinka]

My main idea was to set up a network in my home to share a cable internet connection, well... I spent the last 5 hours trying to troubleshoot my LAN that I just set up, trying to figure out why none of the computers could ping each other...
and right from the get-go, I noticed that the cable that my modem used to plug into my ISP's provided NIC looked very odd. The pin layout was clearly nothing I had ever seen or heard of before... The first thing I noticed were the browns right in the MIDDLE of the layout. (From what I've seen, the browns should ALWAYS be on the far right in lined up with pins 7 and 8) I created a regular straight-through for it, but then the modem wouldn't transmit. It's not a crossover, either, because crossovers don't have the layout that this one did...
This is the actual layout from pin 1 to 8:
1. ORANGE
2. WHITE/ORANGE
3. GREEN
4. WHITE/GREEN
5. BROWN
6. WHITE/BROWN
7. BLUE
8. WHITE/BLUE

Anyway - After having NOTHING left to try, I made another one of those cables, and tried using it for running from my PCs to my hub, and wallah - my network is up and running now.

What the heck is going on here?

Ian

 

[daronwilson]

Interesting Pinout indeed. The concern is not so much which color is in which position, but rather the cable splits the transmit and receive pairs. Pins 1 and 2 should be on the same pair, and pins 3 and 4 should be on the same pair. While the cable you have might work for short distances and/or low speeds, it definately is suspect for solid network connectivity. I have experiened instances where mis-paired cables as you showed would work for short distances, but at 40+ feet the link light would come on and show connectivity but nothing would go anyhwere. The cable was reterminated correctly and it worked fine.

I believe the modem to the computer connection should be a straight cable, so if you are going into a hub/switch you may need to use an uplink port or a crossover cable. Mine goes into my router WAN port which already takes care of that.

I'm unsure from your post which cables you have in place that are running now, so I can't guess much further. The PC to switch/hub cables should be straight ethernet cables, the switch/hub to modem I believe should be a crossover. However, you may want to drop a router/firewall in there anyway, and most of them have a port for the WAN side already configured.

Good Luck! It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[MasterofNone]

Excuse my ignorence on this one, but are we saying the other end is terminated correctly (and to which standard). In order to understand the cable surely we need to know the pin connections. i.e. Pin 1 to Pin 1 (or not as the case may be)

 

[MasterofNone]

Just a follow up on the above, although pins 1 + 2 should be on the same pair, the transmit pairs are infact pins 3 + 6. These should infact be on the same pair and not pins 3 + 4.

 

[IanGlinka]

(I have two NICS in my sharing server)

I think Daron may have a point about lengths 40+ because this configuration will only work on my 10/100 laptop when I use a short cable, though it DOES work on my 10base-t NIC in one of the older computers in my network with my humungous wire (at least 75 feet).

And to clear up any questions about the network's layout, I have a cable modem running into a 10base-T NIC on my sharing server, then another NIC in that computer (10/100)runnning to a 10/100 hub, where the rest of the computers are connected.

Now, I'm not too learned on any wire configurations that don't go by the norm, and I don't understand which wires transmit or receive or what have you... what I do know is, I'm going to try to just make all standard cables now, and run a standard cable from my cable modem to my PC.

Thanks for all the help!
Ian

 

[IanGlinka]

What I really think the problem here is that the patch cable provided by my ISP is not configured correctly (Perhaps on purpose - to prevent geographically wide [community] sharing of a single cable run).

Could the pinouts of this inititial connection "set the tone" for the rest of the network, requiring that all subsequent cables be oriented in the same fashion?

I'm really grasping at straws!
Ian

 

[MasterofNone]

You seem to have a very strange problem. I have a cable modem connected to my PC and this uses a standard straight cable (T-568B)

Pin Color Pair Description
1 white/orange 2 TxData +
2 orange 2 TxData -
3 white/green 3 RecvData +
4 blue 1 Unused
5 white/blue 1 Unused
6 green 3 RecvData -
7 white/brown 4 Unused
8 brown 4 Unused

This is obviously matched at both ends, for a crossover the Pin 1 obviously terminates to Pin 3 and Pin 2 to Pin 6. Are you aware of what the pin terminations are?? The only time I have noted differing pin configurations was envolving Ciscos and DEC servers.

Just for Info (T568-A configuration)
Pin Color Pair Description
1 white/green 3 RecvData +
2 green 3 RecvData -
3 white/orange 2 TxData +
4 blue 1 Unused
5 white/blue 1 Unused
6 orange 2 TxData -
7 white/brown 4 Unused
8 brown 4 Unused

Remember Terminating A config one end and B config the other creates a crossover.

 

[IanGlinka]

The cable modem doesn't use a crossover... it's the same odd pinout on both ends of the cable. I made a new standard cable and replaced it for all ports, and now my network is up and running smoothly.

?????

Thanks for all the help!

(I'm just as confused as you, if not more, except the only difference is I can actually touch and see these cables.)

oy.
Thanks again

Ian

 

[daronwilson]

Sorry, pins 3 and 6 of course for one pair, not sure how that got past my error checking, thanks MasterofNone.

Again, cables not using the appropriate 'pairing' are subject to problems. Without rather complex monitoring equipment it is hard to say how much of a problem, and at what point they quit working completely. I have scanned them with my wirescope 350 and found they dont pass several test parameters, usually related to crosstalk between the pairs. Also keep in mind that different pairs have different twist rates. So on longer runs, one of the two wires may be longer than the other, making an imbalance and throwing off ability to decode the signal well.

At least it looks like you fixed it.
It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[rgroulx]

Ian,

In case you were still wondering:

The reason why split-pair Cat 5 cables work occasionally is mainly due to signal-to-noise ratio. Long cable runs & bad/weak NICs cause high attenuation (signal loss), combine this with a noisy cable (like your split-pair cable; which causes transmit pair signals to "leak" over to the adjacent receive pair, called: Near-end Crosstalk or "NEXT&quot and the end result is a non-coherent conversation.

In the event that this same cable is very short with good quality NICs at both ends, the signal may be "loud" enough so that each transmission is understood by both parties, dispite the amount of crosstalk. Lower speeds (like 10Mbps half-duplex) are more likely to work because the shape of the signal ("digital pulse" or "square wave&quotis less affected by noise. The faster the transmission, the closer together the pulses become, making it more difficult for the NIC to determine if it is a 1 or 0 (especially with added noise).

The end result is that this cable might actually work under certain circumstances, and can drive you absolutely "nutty" trying to troubleshoot it without the proper tools! It is ALWAYS a good idea to IMMEDIATELY throw away (or cut the connectors off) patch cables which are properly determined as "bad, miswired or poorly terminated".


'It takes 2 to Tango'
Ron

 

[MasterofNone]

Have to agree with Ron, troubleshooting without the proper tools does create a hit and miss affair. Having said that, you did note the improper termination of the cable, after noting the same termination at the other end, a simple swapout with a correctly terminated straight through cable would have solved your problems. Thought this is what you did in the 1st place as you did say you did create a cable, but then the modem wouldn't transmit.

Your problems are now solved, so gaining a few cable testers will help you in the future.

 

[IanGlinka]

Thanks again, everyone!!

Now it's on to security... anyone know anything about Zone Alarm?

(No one is responding to my posts in the proxy forum)

Ian

 

[WH0ELSE]

Hey there Ian
i just wanted to say a thing about ZoneAlarm.....the BEST and very easy tool to use to protect your computer, setup is quick and in the begining it will ask you as your programs are accesing the internet to allow it or not....it also tells you if anyone is trying to look into your computer and blocks the intruders stright aways good menu setup for looking into each action yourself... all in all it is an excellent program and i have been using it for a while now, i have tested it!!! WH0ELSE
I think therefore i am.....