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Symptoms of a bad ethernet cable?

Last response: in Networking
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April 30, 2009 6:39:24 PM

I have a situation with a small LAN at an office by which two PC's are unable to acquire a proper IP address and internet connectivity when wired through the patch cables in the wall.

I've done so much as moving the PC and switch directly to the router (to bypass the wall connections) and all is fine.

The LAN uses the IP 10.111.237.* and when I connect the PC's through the wall, for some strange reason the acquired IP address is 192.168.0.* without internet connectivity. Even though the wall connections run to the same router, when I connect the PC's without going through the wall, I get the proper IP address and internet connectivity.

Could a bad cable be the cause of this problem? This is the only thing left that I can possibly think of..

Any input appreciated.

Thanks!
May 1, 2009 1:56:56 PM

Are you sure those cables are going where you think they are? Only way to get a 192 address is if you have the ports set for a different vlan with a 192 scope in the dhcp server. That or those wires are going to a SOHO router.
Do you have any network test equipment where you can trace that line down?
May 1, 2009 2:34:59 PM

I dont have any test equiptment at hand. There is only ONE router in the office and I am 100% positive that the lines end up there, I was able to test that as well. There is nothing in the router configured for a vlan as well.

Thank you kindly for your reply.
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May 4, 2009 2:02:40 AM

192.168.x.x are MS's default addresses if no connectivity is available. Since the PCs work connected directly to the router but don't work when connected through wall cabling, the problem is apparently in the wall cabling. Without test equipment, you're forced into a visual inspection of the wqire mapping on each end of the wall cables. You might get lucky and spot something wrong, but you'll likely have to get at least a network continuity tester...

Bill
June 29, 2009 10:24:36 PM

Sounds to me like that wire is plugged into the management interface on the router or switch.

169.xxx. addresses are what I've always seen as far as MS self assigned IP addresses.

Routers, and Switches, home, and enterprise almost always issue 192.168.xxx ip addresses on their management interfaces (unless configured otherwise).
Tests I would try, are...

Ping the gateway... if you are set to dhcp, and are getting a gateway address... even after ipconfig release/renew then theirs your answer as far as whether or not it's a self assigned address.

nbtstat -a the device - confirm if it's yours, if it does return the hostname of your router, then you know you're connecting to the the right device. You can also test ssh if your up to it (depends on type of router).

If you are not getting a gateway address.. set a static IP etc... - release/renew the NIC and try to ping the gateway 10.111.237.xxx address

Agreed with above, a tone generator would be nice to test the cable.

From this distance, and with limited information, your problem definitely appears like a physical layer problem. However, your description does not lend any evidence towards a bad cable.

Good luck,
-N8
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