Have to face some situation, something physically goes wrong or somebody else screw up your network. This kind of scenario your knowledge will give you confidence but knowledge sometime unable to provide the answer. Something I've learned from the faults and mistakes.
1) Don't panic. When you feel the pressure you are unable to concentrate.
2) Use the tools you have in your hand. ( Trace route, looking glasses, ping , etc...)
3) Isolate the problem. In this step people try to correlate with existing experience !! sometime the prediction is correct some time utterly wrong.
4) Try to contact the right person, provide the correct detail. Persuade the people to work for you is really hard thing. sometime they also bound to some contract that makes that you can get help from them. have some good relationship. Thank them when the problem is resolved. Until they understand they won't put their heart !
5) Hope for the best ! :)