- Watch as Comcast-provided cable modem goes dead. (Not insane yet).
- Swap out cable modem at store. (Not insane yet).
- Plug in cable modem and watch router receive IP address. (Not insane yet. Happy, actually.)
- Notice machines begin trying to reach 220.127.116.11 when using TCP. (Slight insanity.)
- Observe that UDP traffic like NTP updates work properly. (Higher insanity level.)
- Notice that your cannot ping your default gateway. (Insane. Period.)
Apparently when my new cable modem is put on the network, it was given 18.104.22.168 (CPSDNS.selfprov.pa.comcast.net) as its DNS server. This is a really amazing system. Check it out.
orr:/home/richard$ nslookup www.google.com 22.214.171.124
orr:/home/richard$ nslookup www.taosecurity.com 126.96.36.199
The first 188.8.131.52 IP address is reserved. The second 184.108.40.206 belongs to act02.selfprov.pa.comcast.net, which goes to a www.comcast.net Web server. Apparently I was supposed to not use a site like Google as my home page, but something else that would bring me to the Comcast site so I could "self-provision" my new cable modem.
So why could I update time with NTP? Check out the wonders of 220.127.116.11:
orr:/home/richard$ nslookup clock.isc.org 18.104.22.168
That's not correct.
orr:/home/richard$ nslookup clock.isc.org 22.214.171.124
But guess what -- 126.96.36.199 is running a time server.
orr:/home/richard$ sudo ntpdate 188.8.131.52
Looking for host 184.108.40.206 and service ntp
host found : act02.selfprov.pa.comcast.net
5 May 20:56:17 ntpdate: adjust time server 220.127.116.11 offset 0.016223 sec
Hence, my insanity. Some applications worked (NTP), others (TCP to certain Web sites) did not. Good grief. By the way, my equipment came with zero setup instructions. I should have just called tech support earlier and said "the Internet is broken," rather than network troubleshoot!