Why can I not access imgur.com and gravatar.com from Ubuntu but can do so from Windows?

Question

I have this strange problem, I am unable to access imgur.com from Ubuntu !

I have checked the /etc/hosts file, there seems to no entry related to imgur. I can access it from Windows(same connection).

I cannot ping it or traceroute it, I cannot even ping the IP of imgur. I have cleared iptables too, what could be the cause ?

i cannot access gravatar.com too !! I just noticed that sorry.

Running host imgur.com (the same output with google's dns servers)

gowtham@gowtham-hacktohell:~$ host imgur.com
imgur.com has address 23.23.110.58
imgur.com has address 23.23.110.81
imgur.com has address 54.243.128.92
imgur.com mail is handled by 5 alt1.aspmx.l.google.com.
imgur.com mail is handled by 1 aspmx.l.google.com.
imgur.com mail is handled by 10 aspmx2.googlemail.com.
imgur.com mail is handled by 5 alt2.aspmx.l.google.com.
imgur.com mail is handled by 10 aspmx3.googlemail.com.

Running tcptraceroute

gowtham@gowtham-hacktohell:~$ tcptraceroute imgur.com
Selected device ppp0, address 117.199.141.54, port 44995 for outgoing packets
Tracing the path to imgur.com (54.243.128.92) on TCP port 80 (http), 30 hops max
 1  117.199.128.1  17.534 ms  17.764 ms  17.896 ms
 2  218.248.171.102  93.272 ms  26.393 ms  109.985 ms
 3  115.114.130.49.STATIC-Chennai.vsnl.net.in (115.114.130.49)  49.442 ms  47.180 ms  46.981 ms
 4  * * *
 5  ix-0-100.tcore2.MLV-Mumbai.as6453.net (180.87.39.25)  70.085 ms  69.712 ms  70.361 ms
 6  if-2-2.tcore1.MLV-Mumbai.as6453.net (180.87.38.1)  186.862 ms  186.434 ms  185.515 ms
 7  if-9-5.tcore1.WYN-Marseille.as6453.net (80.231.217.17)  181.965 ms  182.963 ms  184.682 ms
 8  if-8-1600.tcore1.PYE-Paris.as6453.net (80.231.217.6)  186.152 ms  184.483 ms  182.950 ms
 9  if-12-2.tcore1.PVU-Paris.as6453.net (80.231.154.70)  191.271 ms  189.655 ms  188.606 ms
10  if-3-2.tcore1.FR0-Frankfurt.as6453.net (80.231.153.54)  187.245 ms  186.013 ms  193.808 ms
11  xe-0-1-0-6.r02.frnkge03.de.bb.gin.ntt.net (129.250.9.57)  288.412 ms  281.124 ms  281.011 ms
12  ae-2.r20.frnkge04.de.bb.gin.ntt.net (129.250.5.217)  352.432 ms  357.071 ms  357.256 ms
13  ae-1.r21.asbnva02.us.bb.gin.ntt.net (129.250.3.20)  391.405 ms  394.961 ms  391.812 ms
14  ae-2.r00.asbnva02.us.bb.gin.ntt.net (129.250.3.114)  378.128 ms  381.786 ms  385.697 ms
15  ae-4.amazon.asbnva02.us.bb.gin.ntt.net (168.143.232.50)  370.938 ms  353.306 ms  351.793 ms
16  72.21.220.55  361.004 ms * 364.525 ms
17  205.251.245.55  368.187 ms  380.907 ms  375.333 ms
18  * * *
19  * * *
20  * * *

I dial the connection using PPoE.

Capturing the stream through Wireshark, I see this

Running curl

gowtham@gowtham-hacktohell:~$ curl -I http://imgur.com
HTTP/1.1 200 OK
Server: nginx
Date: Fri, 11 Jan 2013 12:24:01 GMT
Content-Type: text/html
Connection: keep-alive
Cache-Control: max-age=5, s-maxage=5, must-revalidate
X-Cached: EXPIRED

And telnetting,

gowtham@gowtham-hacktohell:~$ telnet imgur.com 80
Trying 23.23.110.58...
Connected to imgur.com.
Escape character is '^]'.
HEAD / HTTP/1.0


HTTP/1.1 200 OK
Server: nginx
Date: Fri, 11 Jan 2013 12:25:11 GMT
Content-Type: text/html
Connection: close
Cache-Control: max-age=5, s-maxage=5, must-revalidate
X-Cached: HIT

Connection closed by foreign host.

Answer 1

From what I have seen of your curl output, you can access it.

If you can't see it on your browser, try with another browser.

My curl output.

curl -I http://imgur.com
HTTP/1.1 200 OK
Server: nginx
Date: Sat, 12 Jan 2013 03:21:00 GMT
Content-Type: text/html
Connection: keep-alive
Cache-Control: max-age=5, s-maxage=5, must-revalidate
X-Cached: HIT