Someone please help me understand why my CAT5 isn't supporting 100MBits

[SunnyD]

I have a spoolpak of CAT5 solid core that I got a bit over a year ago. I found the reason I wasn't able to connect properly was because of this cable.

I have a run of about 40 feet in length of it going from my machine to my switch. When I try to connect to it, the DHCP server assigns me a 169.254.x.x address. Well, at least that's what I get. There's activity on the line, but assumedly a lot of packet loss. If I force my NIC down to 10MBit (10BaseT) the world is happy once again.

But why would this be happening? Any ideas on this?

SunnyD

 

[Hard_Boiled]

I used some old cable that I took from my office after we first wired it for networking a few years ago. Wired up my house with it and everything was fine, because I was also using a bunch of old ISA 10 MBit network cards that I acquired from work.

So I decided recently to buy some 10/100 cards and a switch. I have also run different cable to other portions of my house. I have the same problem as you, the original cable that I used will not work at 100 Mbit, only 10. Took me a little while to figure out why it wasn't working.

The odd thing about the cable I first used, was that although it had 8 wires and they were all twisted in pairs, the pairs were stuck together. Most cables I've worked with have the twists but the pairs are still able to be seperated.

I think some older crummy cables just aren't rated for 100 Mbit speed. I thought all Cat5 cable was, but apparently not.

 

[rrmccabe]

When you say it isn't supporting 100 speeds, I am assuming it is working at 10??

There are several reasons that cable may not work. The first thing that comes to mind is a bad spot in the cable or improperly terminated ends. Even though the wiring scheme may be correct and it check OK for continuity, it may still not work. Cable that is not twisted properly or has too much untwisted near the plug (should be less than 1/2") will have crosstalk and not work right at the higher speeds.

I have seen many cables that will operate at 10 and not 100 because of the above mentioned issue. That is why Cat 3 cable which has 8 conductors and the same wiring will work at 10 base and not 100. It does not have the right "twist".

I hope this helps.

Rich McCabe
Computer Technologies.

(Anands very first review partner!)

 

[rrmccabe]

Also, in case you are not aware, a 169. address is something that is assigned by windows when it can not get a dynamically assigned address. That is perfectly normal in a situation where you are not getting a good connection.

Rich

 

[JackMDS]

Did you try to put the two computers, and a switch close by with 3? cable, and see if they run 100Mb/sec?

 

[Tallgeese]

Sunny:

Bit confusing, starting two closely related threads about the same issue...note Jack's question which was already answered in your other thread.
Why don't you make it simple...kill the other thread, and keep going with this one.

P.S. Check your wiring standard first. Make sure you used either 568A or 568B on both ends.
BTW: if your ends are wired straight across in matched pairs (as in: oranges, greens, blues, then browns) it won't work well, if at all, at 100TX.

 

[spidey07]

My guess would be the terminations. If not then maybe just a bad spot of cable.

 

[Tallgeese]

Did you run this cable through any walls, floors, etc.? You mentioned the basement in the other thread.
If so, it could have been damaged (cut, kinked, pinched, folded, spindled, mutilated) when it was installed.

Or, you could just have a sucky brand/vendor of cable.

 

[Nutz]

Not to mention a bit of EMI mucking up the path.

 

[ktwebb]

At 40 feet, sounds like you might have terminated the ends yourself, no? If you did make your ends, recrimping would be the first thing I would do. A kink may be the culprit but UTP will bend significantly without deterioration.

 

[SunnyD]

Okay, first, let me say thank you for all the replies. I didn't know cabling was such an "art". Wow, shows you how much I know.

First to Rich - cool, looks like I finally have a network engineer on my side. I don't think there's anything physically wrong with the cable, as I made a second length of it, and suffer the same problems. And yes, I know about those 169 addys. It's synonimous with "it just don't work".

TallGeese, it does run thorugh a wall/floor through the mudroom and across the basement floor. I don't think there's any real close power conductors to it, but I could be wrong.

>>> Or, you could just have a sucky brand/vendor of cable. <<<

The above is my guess. This is what I have: BICCGENERAL C MPR/CMR (UL) CMG 4PR 24AWG 75C 1WC---VERIFIED (UL) CAT5 ....

I will check the wiring standards tho, I think I may have just done straight-thru connections.

SunnyD

 

[SunnyD]

TallGeese - THANK YOU.

This is why you people are here - because people like me are idiots. I just cut off the ends on the original run of cable that I thought was suspect, crimped on two new ends conforming to 568B on both ends - and I'm posting this message on that very same cable on a 100MBit autosensed link to my original switch.

You've solved me 2 months of headaches.

Thanks again.

SunnyD

 

[skeletal29]

ARE you using cable ?If youa re getting that 169 ip adreress turn off all the equip for 90 seconds.YES 90 DONT BE CHEAP.and restart and everything should work fine