Weird Network Behavior

We had a really weird thing happen at the office today, and I can’t figure out for the life of me why it is doing what it is.

One of our clients has a web site that we are not able to reach from behind our SonicWall firewalls. It is not being blocked by our content filtering. We just do not get any response from it when trying to connect to the standard web port (we can ping the box though through the firewall).

So in a fit of desperation (someone really needed to grab data off the site), we configured a laptop with with an external static IP address, attached it directly to the Internet (outside of our firewall) and quickly downloaded what we needed. Now here’s the funny part, I plugged the laptop back into the network on the inside of the firewall and rebooted. However I forget to re-enable DHCP, so I was still configured with an external IP address, gateway and DNS server. I logged into the laptop, and launched my web browser and started surfing the Internet just fine.

But that can’t be! My laptop is configured with an external IP Address, it has the wrong default gateway set, and all of its DNS server settings are for outside the firewall (in theory it should not know about any internal hosts or routes). How can this be?!? How can I be getting access to things externally on the Internet? This just doesn’t seem right. Does anyone have any ideas?

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