cable issue

i was at a friends house the other day and he had another guy wireing a room with ethernet cable. he has 2 pcs there neither of em is getting an ip address from the dhcp.

plugged in my laptop and got an connection to the internet. plugged in his laptop, got a connection to the internet.
both pcs worked finde in other rooms.
my educated guess is that the guy who wired the stuff did some crossover cables which are not beeing auto detected by the pcs.

any ideas / suggestions on this issue?

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Comments

JeanM

To confirm - over this ethernet cable "A" in the room laptops work fine, but the computers do not?. The same computers that do not get ip over this cable, get ip and connection over another cable "B" in another room?

So, that cables "A" and "B" have internet connection only under certain conditions correct?
PC's get internet connection only on cable "B" ?
Laptops get internet connection either on cable "A" or "B" ?

Where are all these cables connected to? Is there a switch or something with mac / port assignment?

Get one of those cable testers to check if the cables are straight or crossover?

martell1000

yes this is correct. everything is connected to an unmanaged switch. my plan is to bring another switch in and connect it to cable "A" and then connect the pcs to it. i will be there again on next thursday and will report back in if it worked out.

MAC_Addy

I'd first use a cable tester to test the connections.

Jon_Cisco

On most cables with clear clips you can see the wiring and determine if it is a crossover cable.
You might also want to bring along a straight thru cable for testing.

Good Luck

martell1000

went there yesterday and plugged in a switch, worked like a charm for about 5 minutes, then it produced sings of a flapping interface, on off on off ....
pings got lost at about half of the time. also brought a long ethernet cable to connect the pcs directly to the router, worked 100%. checked the cables in the wall jack, it was crossover, but something seemd to be wrong with the cable / and or the wall jack although i couldnt see what exactly it could be. think we are going to replace bothe of them with new equipment, since the guy who installed it first got the stuff out of an "old cable box" at his workplace...

tasman35

martell1000 wrote: »

went there yesterday and plugged in a switch, worked like a charm for about 5 minutes, then it produced sings of a flapping interface, on off on off ....
pings got lost at about half of the time. also brought a long ethernet cable to connect the pcs directly to the router, worked 100%. checked the cables in the wall jack, it was crossover, but something seemd to be wrong with the cable / and or the wall jack although i couldn't see what exactly it could be. think we are going to replace both of them with new equipment, since the guy who installed it first got the stuff out of an "old cable box" at his workplace...

First what kind of cable is it...cat5 cat5e cat6 and also what kind of jack are on the end of the cable. cat5 cat6...maybe old cat 3 jacks...also look at the jacks there should be some kind of color code sticker on the side of the jack one should be labled a and other labled b make sure they are both punched down to ether a or b they have to match...and you if your using cat 5 cable use cat5 jacks...the strands in the cat6 cable pairs are thinker than cat5 cable so you will have some play when you punch down a cat5 cable to a cat6 jack...also look at the end that you have next to the switch...did he put jacks on or did he crimp rj45 mods on if so cut them off and put on a jack and use patch cables to connect to the switch...it will make it easier to trouble shoot and the most IN PORTENT this is LABEL EVERY THING....

I have been installing cabling for networks for almost 20 years if you need more help just let me know...good luck...and label every thing...

martell1000

@tasman35: problem solved: it was indeed the wall jack. seems like the jack the other guy got out of his junk box was somehow broken or not intended for use with the cable (cat5) ... replaced it the other day and everything works fine now.

thanks for all the help guys!