This issue has been killing me. I am working on a network where Twitter.com will not display in a web browser anywhere inside the network. I can ping it, I can tracert to it, but I cannot view it on port 80. This will be a long post since I've tried a lot of things and seem to have narrowed the issue a bit.
Environment: Corporate network with a Sonicwall Pro 2040 and a Cisco router. Router seems to be a non-issue in this case because when I plug a laptop directly into the router (same port the firewall plugs into) twitter.com works correctly. The issue seems to be with the Sonicwall. DNS is using Google's servers as forwarders, no strange entries there. No AV or web filtering in effect on the LAN or WAN interfaces and nothing explicit that I can find in the Sonicwall config that would affect this.
Testing: I tested a number of connections to Twitter.com from inside the network and outside. Here is what I found:
Outside the network: When I ping twitter.com and www.twitter.com
, I get a random address from Twitter's block. If I take any of those addresses and enter them in a browser, they resolve to twitter.com and the page loads.
Inside the network: When I ping www.twitter.com
, I get a random address from Twitter's block. If I take any of those addresses and enter them in a browser, I get the generic 'cannot display the webpage' error. However, I can ping and tracert to all of the addresses. This makes me think the issue is with http (port 80) traffic only. Attempting to telnet to twitter.com on port 80 seems to confirm this- it does nothing. The odd piece is this: when I ping twitter.com, as opposed to www.twitter.com
, I get the same address every time. It's a valid Twitter address, but it does not resolve to their domain name. If I put it in a browser, it maintains its IP address as the URL name and the site works. This particular IP address behaves the same way outside the network- if I enter it in my browser at home, it will not resolve, it will simply display Twitter.com's website using the IP address as the URL.
We then tried putting in a custom host entry so that a computer would use the IP address that actually works as the destination for www.twitter.com
. Putting that in the browser again resulted in 'cannot display the webpage'. We changed the host entry to point cnn.com to the same Twitter IP address and it resolves to the Twitter site and displays it.
So my mystery at this point is this: What could be filtering out any port 80 traffic to twitter.com (apparently based on the domain name)? Also, why do they get the same IP address every time they ping twitter.com when every other computer we test this on gets a random one?