As many of you know, I run a computer shop, I am fairly well versed in basic networking, routers, and internet connections.
This week I got a weird one.
The hardware: Dual core Vista Home Premium, 2G ram, 250GB HDD
Modem: uBee DDM3513 Docsis 3.0 Cable Modem
Machine is plugged directly into modem via ethernet cable, no router.
Customer calls, can’t get internet to work. Customer has had Comcast onsite techs out, who say its the computer. Connection works with Comcast techs laptop, works with my laptop.
I remove a few viruses, go through the usual internet connection stuff.
No browsing, the machine will not seem to connect to comcast DNS.
So I try manually specifying both Google DNS and Open DNS addresses for DNS resolution. - Nada
2 of 4 packets lost - destination unreachable
I can browse to the modem configuration page on the modem, so its not like I have a dead ethernet card.
Replace cables and network card - Nope
Swap for motorola Surfboard Cable Modem - Nope
Take machine back to shop, plug into our router, works perfectly
Tried plugging directly to our modem, works perfectly.
Wipe and reload machine to eliminate possibility of some exotic setting or residual virus damage causing problem.
Back to customers house - Still nothing
On a hunch I try hooking up a router to customers modem and PC to router.
Clouds part, angels sing, internet flows like champagne in the hamptons.
The question: Why?
What would stop a fresh load of windows from pulling DNS from any old comcast connection but once a router asks, well sure here ya go, browse away.