Facebook

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Hi,

today I was called to a customer because he could not access facebook - but all other domains.

The customer runs a small network with tinydns and an external dnscache.
His claims were justified: tinydns was working fine but
  dig a www.facebook.com or
  dnsqr a www.facebook.com
just didn't resolve.

I noticed that 
  dig @ns1.facebook.com a www.facebook.com
results in:

; <<>> DiG 9.5.1-P3 <<>> @ns1.facebook.com a www.facebook.com
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 3225
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 7, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;www.facebook.com.		IN	A

;; AUTHORITY SECTION:
www.facebook.com.	900	IN	NS	glb01.hkg1.tfbnw.net.
www.facebook.com.	900	IN	NS	glb01.ash1.tfbnw.net.
www.facebook.com.	900	IN	NS	glb01.lhr1.tfbnw.net.
www.facebook.com.	900	IN	NS	glb01.snc1.tfbnw.net.
www.facebook.com.	900	IN	NS	glb01.dfw1.tfbnw.net.
www.facebook.com.	900	IN	NS	glb01.ams1.tfbnw.net.
www.facebook.com.	900	IN	NS	glb01.sf2p.tfbnw.net.

;; Query time: 140 msec
;; SERVER: 204.74.66.132#53(204.74.66.132)
;; WHEN: Thu Mar 11 01:06:03 2010
;; MSG SIZE  rcvd: 218

which is strange.
It seems that not only the domain 'facebook.com' has name servers but the host 'www.facebook.com' has another set of 7 name servers.

Later at home (where I have a similar setup) I tried it again:

dnsqr a www.facebook.com

timed out.
However, when I ran the command the 2nd, 3rd, 4th etc. time it returned an IP number.

Both servers run Debian Linux.
The difference was that my home server had the djbdns package installed (which seems to be more standard) while the other server had the dbndns package installed. This package contains patches to support IPv6.

Not sure whether this was the problem I installed the djbdns package on the client machine as well.
Yes, and it worked as well.

While I solved the problem (at least from the customers viewpoint) I wonder whether somebody else made the same experience. Facebook must have changed something before the system had been working for months without any problem.

Did anybody make similar experiences?

Regards,
Bernd
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