Re: curious behaviour of DNS caching only server
What exactly did you set up? I didn't set up any DNS in 12.04 and it seems to have its own caching nameserver by default. After doing host facebook.com and host www.facebook.com, dig facebook.com came back in:
;; Query time: 105 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Mon Nov 26 23:51:50 2012
;; MSG SIZE rcvd: 126
Web browsers often have their own DNS cache, so it is possible that TTL expired from your caching nameserver and it had to fetch fresh info for dig (do you forward to your ISP's nameservers or use root servers?).
I used to run bind9 using root servers for caching DNS many years when my ISPs DNS lagged and I used Linux as a pppoe router with a DSL bridge modem. But I have not done that for a long time because the FreeBSD based modem/router I have had for about 10 years does its own caching DNS (and resolves local netbios names for machines that do Windows networking).
i5 650 3.2 GHz, 8 GB, nvidia GTX 1060, 32" 1080p & assorted older computers