No, I Will Not Fix Your #@$!! Computer → DHCP issues on one PC

I've been wrestling with this issue remotely for a few hours now, but am going onsite tomorrow morning. Here's the problem:

The network is a single subnet driven by a TZ210 as the DHCP server and router, with no VLANs, managed switches, port-based ACLs, or any of that kind of stuff. The client had some of their data wiring consolidated (basically created more home runs and eliminated some of the switch to switch to destination runs) and after the job was done, all worked well. The network was up and running on all of the PCs. This was a week or so ago.

Now, on one PC, it is not pulling DHCP. The interface is live because it's pulling a 169 address. Static IP info does not work, either. If another PC is swapped in at this station, it connects to the DHCP server just fine. The interesting thing is that if the problematic PC is plugged in at another station, it too connects to the DHCP server and joins the network without a problem.

Sounds to me like we've ruled out hardware on the PC (it works at another station) and wiring issues (a different PC works fine at the same station.) I'm not sure what I'm going to find when I go onsite tomorrow given that the wiring scheme has changed and I have not seen it yet, but I hope it's easier to troubleshoot when I have all of the hardware in front of me.

that seems odd, assuming everything you said is accurate.

curious to read what you figure out when you are on site.

who did the PC maneuvering for you, on site? is it possible they gave you wrong information when moving PCs?

what is the DHCP range? what is the lease time?

Is the problematic PC's BIOS up to date?

Tried swapping the ethernet cable between stations?

I doubt the BIOS is up to date. It's an Opti 760 or something like that. The ethernet cable to this station runs up a pole and across the ceiling (it's in a warehouse), maybe 75 feet end to end.I'm hoping that there was some miscommunication on the part of the people who were helping me onsite. They have technical skills, but not enough to know what to check prior to calling me.

The DHCP range is not contiguous (it's .30-99 and .110-139 or something like that) but there are plenty of open addresses right now. 1440 minutes is the DHCP lease. The wiring changes are actually in preparation for a new network schema with L3 switches and VLANs in order to make their addressing design more logical.

Any chance that the network cards in the two systems might have different speeds and/or configurations. If it's a case of a lower speed card being able to connect, but a higher speed card can't, then that may indicate that there is a problem somewhere in the cable run.

The TZ210 looks like it handles multiple speeds, so (even if not the case above) you might try dropping the speed of the card in the machine that isn't working. If that does the trick, then have a closer look at the cable.

Good idea, I'll check that out tomorrow.

I've seen PCs have issues when they were set for AUTO but worked fine when a speed was hard configured...

Another idea/option...

Is a pair of conductors reversed in the 'new' cabling - i.e. a Tip/Ring swap?

Some NIC's are able to cope, some, not so much...

I'd get the cable contractor out to verify the wiremap, myself...

Make sure the physical is good (since it's what was most recently changed) before diving into more obscure stuff like BIOS revisions (that worked fine before the wiring was changed, anyways)

i was thinking the same thing, but i ruled it out once he said the computer that wasnt working worked on a new drop and the pc that was moved over to the drop in question had no issues grabbing an IP address.

again, that is assuming what he instructed the person on the phone to do was accurate.

hopefully we get an update from him since he is on site, today.

I'm back, and I wish the problem/solution had been more interesting.

I went out there and was led to the PC that was having issues. It was, of course, not the one that I was picturing, which meant that the person I was dealing with gave me bad info right out of the chute.

The PC is fed by a long floor-to-warehouse-ceiling drop that has been in place for years, and the PC itself is not new either (GX620 with a Broadcom NetXtreme NIC.) I verified again that it was receiving a link local address, which i was. I changed the link speed to 100 full duplex, 10 full, 100, half, etc. with no love. I noticed that it took a long time to go from "network cable disconnected" to "identifying." I unplugged the CAT5 and plugged it into my laptop, which is a Latitude E6410 with an intel NIC. It would not even recognize the cable's presence. I plugged it back in to the desktop, and after about 15 seconds, one of the lights on the NIC came on. I pulled the cable out again and looked at the connector; about half of the wires were noticeably shorter than the others, almost as if the cable had been pulled really hard horizontally.

So, I cut off the offending connector and re-terminated it. No more problems. I suspect that the laptop they used to test the drop with had a 100mb or otherwise more tolerant network card that accepted the honked up wiring in the connector.

Glad you got it figured out Moffetts .... for some reason, I keep hearing Gary A Donahue's admonition
in his book Network Warrior, "Physical Layer First!"

Regards