This customer uses her laptop at her parents house (wireless), and at her city apartment (for school… via a ethernet connection to the ISP that handles the buildings internet).

She just returned to the apartment, and found that the wired internet doesn’t work.

She disabled Trend IS, and that was the extent of her technical know-how.

The ISP technician says he can “see” her PC on their network, so the problem must be with her laptop.

When I get there, it looks like it should work. An ipconfig returns realistic looking IP addresses for the IP address, default gateway, DHCP server, and DNS servers.

I disable Trend IS, and anything else that could be causing the problem.

But ping will only work to the laptops own IP address.

An ipconfig release and renew doesn’t help.

In fact the renew takes about 1 minute to complete, then gives an error message about being unable to complete… yet it obtained the same correct-seeming addresses from before… so the network is working… and DHCP must be working, yet as soon as the all the network settings are in place, no further network traffic occurs.

In fact, looking at the activity in the local area connection status window, I can see packets being sent from the PC, but none being received.

This is highly unusual. I start up my own laptop, and plug it into the network… and it exhibits the exact same behaviour.

Aha! It must be something with the ISP (possibly a faulty network device (router, dhcp server, LAN port, whatever).

I call the ISP, and I eventually get to talk to someone friendly and helpful. Its funny how they don’t brush you off, if they hear you talking about ipconfig, dhcp… as they can tell that you know what you’re talking about.

Anyway, he admits that he can see a problem (the PC is being given the wrong DHCP IP address, so their security is blocking the laptop access to the net.

I suggest a workaround by entering the IP addresses manually… he agrees (but says the IP address could change if the DHCP server decides to change it, and then the internet will stop working).

He also escalates the problem  to “level 2 support”, and cannot give a timeframe for a resolution.

I explain this to the customer, and say that the ISP must instruct her on how to revert the settings back to automatic DHCP, etc…

She just needs the internet for the next 2 days (needed for pre-exam study), after that, she doesn’t care.

Anyway, once the internet is all working again, I re-enable all the stuff I disabled, double check everything, and I’m on to my next customer.