I recently spent about two weeks trying to figure out why an intercontinental connection between two of our sites was broken. Not really my job, I just care about application level, but the network guys were beyond useless.
In the end I had the problem isolated to a specific network segment in India, which made them look at the right system and fix things. The reason? “We put up a firewall the day your problems started which blocks everything, if we allow your connection it works”.