188.8.131.52 not responding to DNS queries
By default, my droplet (Ubuntu 13.04 x64) was set up with two DNS servers in resolv.conf: 184.108.40.206 and 220.127.116.11. In debugging why my client requests to Twilio were slow or failing, I found out that host resolution was timing out half the time and eventually discovered that 18.104.22.168 is not responding to queries from my droplet:
dierks@sharkodile:~$ host api.twilio.com 22.214.171.124 ;; connection timed out; no servers could be reached
It works from my desktop in my office:
~ $ host api.twilio.com 126.96.36.199 Using domain server: Name: 188.8.131.52 Address: 184.108.40.206#53 Aliases: api.twilio.com is an alias for public-vip374d1ca4e.prod.twilio.com. public-vip374d1ca4e.prod.twilio.com is an alias for ec2-174-129-254-101.compute-1.amazonaws.com. ec2-174-129-254-101.compute-1.amazonaws.com has address 220.127.116.11
This could be specific to my droplet or to DO. It's not a big concern for me (I just replaced 18.104.22.168 with 22.214.171.124 in my config; Level3 apparently doesn't want the public using 126.96.36.199 in the first place), but I thought I'd see if anyone else was seeing this problem and possibly contribute if anyone else is trying to debug similar problems.