We're hiring! We're hiring engineers in the US and in our development center in Granada, Spain. This means we are reviewing lots of resumes and doing initial phone screens. One of the simple phone screen questions I love to ask is related to debugging a DNS problem (except folks don't know yet there is a problem with DNS). There is really no single correct answer. There is one really poor answer: giving up. In the process of debugging the problem, candidates often come to "ping a public IP address somewhere". I ask them to give me specifically which IP address they know is up and running. I've been amazed by how many folks in Spain know of Google's public DNS service and know it's IP address by heart: 220.127.116.11.
The most recent XKCD comic illustrated the point about the importance of the 18.104.22.168 DNS server. Phone screen question busted.