Starting last Thursday, I am experiencing intermittent problems with my home cable Internet connection.

After investigating what was going on, I came to the conclusion that my Linux Router/Firewall was not able to get a lease from my ISP. I confirmed my findings by disconnecting the linux box and connecting my laptop directly to the cable modem. WireShark showed the same as tcpdump did on the linux box: Whilst I was sending out DHCP DISCOVER packets, I got no DHCP OFFERS whatsoever from the almighty DHCP server.

I decided it was time to call my ISP’s helpdesk…
After dialing the number, a computer voice told me that they tested the modem and the ISP’s infrastructure is working perfectly. Now this is already enough to work on my nerves as there might be a million other things wrong with my ISP’s infrastructure besides the poor cable modem. Next a first line helpdesk guy picked up the phone. After I explained him I did not see any packets returning to my DHCP offer, he told me to ‘click start –run – cmd.exe – ipconfig/renew’… sigh
After pushing the guy a little, he finally came to his senses and to the conclusion that it might be a cable modem related issue but he immediately covered his back by stating ‘all costs for sending a technician might be for my account if the problem was not related to the cable modem (which is owned by the ISP)’ …sigh again.

So I asked the guy: ‘How can I be sure it is the cable modem according to you?’ He answered to unplug any device from the modem and wait for 2 hours (lease expiry) before reconnecting any device and then try to connect again. Fair enough, so I unplugged the RJ-45 plug from my cable modem and waited for two hours. After two hours still no lease.

The next day, I called the helpdesk once more (again a voice stating that the modem is working like a charm) and this helpdesk guy tells me that what his colleague said was wrong. I needed to unplug the modem, wait two hours (apparently the lease expiry + reset time of their setup) and try again. He told me that the old model of (CDLP) modem I have is known to block DHCP offers from time to time. The new (DOCSIS) modems do not have this problem and reset far easier so he said.
Another two hours of waiting later, I was able to get a lease right away. Happiness followed and the universe was in balance again or so it seemed.

The joy was only for a short time as today; my Internet connection suffered an outage of one hour once more. Now, I understand that my Internet connection has no SLA whatsoever but I do need this connection to work from home and I never had this frequency of outages in the past. The logs of my linux box showed the same problem. It could not renew his lease during the time of the outage.
Another call to the helpdesk and they are sending over a technician to investigate. Although the support guy still said that the techie house call might be invoiced to me if the problem is not related to my modem…. The technician coming over would be the judge of that.
Hopefully the onsite-techie will replace the modem this Friday or otherwise I am very close to short circuit the modem so I DO get a NEW one and good service once more.