I had a problem with traffic black holing all of a sudden everything going nowhere with Wipro once.

What we found was that suddenly a some ports with traffic distended for the internet bounced and the black holing started. A Wipro rep proudly announced that they had caused the port bouncing. You see they found that someone (Wipro... but they didn't know it was their own people at this point) had cabled around the firewalls a year earlier because something wasn't working, and never hooked them back up.

So now we were cabled to the firewalls properly... the firewalls that as far as anyone could tell had nonsensical configs that all pointed to a null route.

So for at least a year, maybe more, there was no firewall. The end customer was a large financial institution.