At $PreviousEmployer we sold a security appliance that in a typical network, never sent traffic out its interface - traffic was routed to it, inspected, and tra

At $PreviousEmployer we sold a security appliance that in a typical network, never sent traffic out its interface - traffic was routed to it, inspected, and transmitted out a different interface. To keep any potential upstream switches happy, we would send a periodic Ethernet frame with dummy data just to populate MAC-address tables/caches. Well, nobody was supposed to ever see this frame... One day a customer, a very large ISP, ran Wireshark on their network to troubleshoot something unrelated to our gear and saw these bogus Ethernet frames containing pirate quotes and hacker jokes. After confirming the source MAC to match our appliances, they immediately called a sev1 issue and assumed their network was compromised and started ripping out our gear left and right. It ended up going way up the chain of command at both the customer and our employer. Soon there after, we released a patch and it simply echoed "$Employer Switch packet" - the fun quotes and jokes were no more. Although, some say there is a hidden config line you can set to bring them back, but it's not documented.