We support a multitude of customers , from hosted servers, to hosted phone systems, and hosted internet for several as well. So when our network goes down, so do theirs. We have structured for fail over on most situations but as the IT world knows you cant plan for everything. When the critical happens I rely heavy on my team, together we work diligently to isolate the root cause of the issue and fix it. As well as to make sure we have a contingency plan in the event the same issues arises again.