Why is www.google.com not reachable?

Question

I just set up a new machine on my home network running Ubuntu 10.04. For some strange reason I can't reach www.google.com. All other domains work fine, even googles sub-domains like docs.google.com. I have no idea what the problem is.

curl http://www.google.com/

curl: (6) Could not resolve host: www.google.com; nodename nor servname provided, or not known

ping www.google.com

ping: cannot resolve www.google.com: Unknown host

dig www.google.com

; <<>> DiG 9.7.3-P3 <<>> www.google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 51258
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

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

;; ANSWER SECTION:
www.google.com.     54813   IN  CNAME   www.l.google.com.

;; Query time: 46 msec
;; SERVER: 192.168.3.1#53(192.168.3.1)
;; WHEN: Tue Jan 10 14:48:35 2012
;; MSG SIZE  rcvd: 52

The google.com 301 redirect is reachable, while www.google.com is not.

Answer 1

Your dig returns incomplete results, here's what I get:

$ dig www.google.com

; <<>> DiG 9.2.1 <<>> www.google.com
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 54679
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 4, ADDITIONAL: 4

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

;; ANSWER SECTION:
www.google.com.         0       IN      CNAME   www.l.google.com.
www.l.google.com.       263     IN      A       209.85.229.99
www.l.google.com.       263     IN      A       209.85.229.103
www.l.google.com.       263     IN      A       209.85.229.104
www.l.google.com.       263     IN      A       209.85.229.105
www.l.google.com.       263     IN      A       209.85.229.147

;; AUTHORITY SECTION:
l.google.com.           33378   IN      NS      ns3.google.com.
l.google.com.           33378   IN      NS      ns4.google.com.
l.google.com.           33378   IN      NS      ns1.google.com.
l.google.com.           33378   IN      NS      ns2.google.com.

;; ADDITIONAL SECTION:
ns1.google.com.         193146  IN      A       216.239.32.10
ns2.google.com.         193146  IN      A       216.239.34.10
ns3.google.com.         193463  IN      A       216.239.36.10
ns4.google.com.         193146  IN      A       216.239.38.10

;; Query time: 147 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Tue Jan 10 16:23:30 2012
;; MSG SIZE  rcvd: 268

In particular the answer obtained by your dig lacks the A records for www.l.google.com.

I would use wireshark or similar tool to see what DNS queries were sent where and what DNS replies were received. Compare results on working and non-working PCs.

Answer 2

When you diged for an A record, your DNS server returned a CNAME with no extra records. This is quite strange and may indicate the server can't resolve www.l.google.com.

"google.com" worked because CNAME can't be used with the "@" record, so A records must be returned directly. Maybe the DNS server 192.168.3.1 is filtering out l.google.com domains. Check if dig @8.8.8.8 www.google.com gives you A records. If so, you may want to change your DNS server.

Answer 3

There seems to be some problem with DNS resolution. Maybe some issue with ISP's DNS cache. You can directly check using Google's DNS server "8.8.8.8" and check.

lab@x:~$ dig www.google.com @8.8.8.8

; <<>> DiG 9.7.3 <<>> www.google.com @8.8.8.8
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 30985
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 0

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

;; ANSWER SECTION:
www.google.com.     81660   IN  CNAME   www.l.google.com.
www.l.google.com.   113 IN  A   74.125.236.84
www.l.google.com.   113 IN  A   74.125.236.80
www.l.google.com.   113 IN  A   74.125.236.81
www.l.google.com.   113 IN  A   74.125.236.82
www.l.google.com.   113 IN  A   74.125.236.83

;; Query time: 42 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Thu Jan 12 00:25:58 2012
;; MSG SIZE  rcvd: 132

lab@x:~$ 

If this is working fine then you may change

lab@x:~$ cat /etc/resolv.conf 

to use this DNS server and then try sending a curl request.