We use Comcast cable internet at home. The reasons are long and painful, but it basically comes down to not having any other viable options where our house is. Because we live in an unincorporated part of our county (outside any city limits) we’re considered rural. Which means, I suppose, that bad service is what we should expect.
Ever since we started with Comcast, we’ve had great connection speeds, but bizarre intermittent outages. Abut a month ago, we started to get redirected to a strange Comcast internal search engine page because of “dns failures.” Except I find it hard to believe that Comcast couldn’t figure out how to resolve google.com or yahoo.com and had to send me to a walled garden search.
This led to a week or so of crazy madness with Comcast techs, who at one point completely shut off my service in an attempt to allow me to turn off their “helpful typo search corrector” from my comcast account console. The Comcast service techs blamed variously, the age of the OS I was running (OSX 10.6.4 in one place, and Centos 5.4 in another) or Firefox, or Chrome. They refused to acknowledge that being unable to nslookup google.com from a command line is a strong indication that it’s not a browser problem.
Armed with the knowledge that at least part of the problem is Comcast’s incompetent (or intentionally misconfigured) DNS service, it was time to go shopping for an alternative.
I tried using OpenDNS for a week (208.67.222.222 and 208.67.220.220), but that seemed slower and more erratic than Comcast’s service. A week with Google’s Public DNS (8.8.8.8 and 8.8.4.4) didn’t seem to work any better. Most recently I switched to DNS Advantage (156.154.70.1 and 156.54.71.1). So far, this seems like a working solution. Happily, all that needs to be done is to update the DNS settings in the border router in the house (which points to itself as a DNS server for dhcp clients). Of course, the problem might be inside the border router, except that I have a sniffer on the wire between the border router and the cable modem, so I can watch the traffic there for anything unusual.
I can’t find any reason why OpenDNS or Google’s Public DNS shouldn’t have been just as good as DNS Advantage – unless there’s something wacky in the way Comcast runs their network that makes these fail. All three services are 20-30 milliseconds away from me, so that’s clearly not the problem.
Anyway, here’s hoping that this remains a viable fix long term, and that I won’t have to go play around with this every few weeks because Comcast is playing cat-and-mouse to make sure I get the maximum value-add from their broken DNS service.
Meanwhile, I’ve written some scripts to try and collect long-term reliability data on Comcast’s network as seen from home, to try and figure out what, if anything, I can do.