Here’s what happened: starting yesterday, a machine in my lab suddenly couldn’t access the Internet. I usually use that machine as a proxy, because sometimes I need an NCTU IP address for looking up papers. At first I thought Squid was broken, so I spent a long time tweaking the configuration—only to realize the issue didn’t seem to be Squid. Then I was shocked to find that I could SSH into the machine, but it couldn’t connect outbound.

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