Google Professional Cloud Network Engineer

I won't tell the same story over and over because it should be clear that you need to study the tracks outlined in the prerequisites for this course. The part I needed to do mandatory is Coursera and the Qwiklabs before even becoming eligble for a voucher.

In this case Pluralsight is the same as Coursera, Philipp Maier is showing the same videos.

Linux Academy is totally different and is more focused on the exam itself; I like it :-)

There is no need to study for months unless this is your first google certification exam and if you are not familiar with network topics in general.

As a lot of questions are scenario based it is important that you really understand the concepts and the flows. Learning everything by heart is not enough. You need to be able to visualize the solution and often it is the most logical one that is correct unless the question has some words in it to make it just the opposite. That is one of the most important tips: read the question and read it again. Picture yourself what is being asked and if you don't read it again. If you have the answer in mind you then simply choose the one that is shown. In doubt most of the time you can skip 2 out of 4. So you need to read those 2 answers, compare them and look what matches best. Sometimes it is just one word that is different so reading and understanding is the most important part.

That goes without saying for all exams. 

For this one you need to be familiar with network concepts in general, not only Google or SDN's. If you are e.g. a CCNA it will definitely help. The knowledge concepts of VPC, (multi)region, zones in relation to the components you can use is heavily tested. As there are the various Loadbalancer options you need to know which one to use in a given scenario. But also what to do if components have no public addresses and still need to use the internet. Also the various connections with their (dis)abilities to and from on premise, other providers and GCP is a topic. And as always IAM for almost every service that you have in this course is questioned.

Also be familiar with CLI commands as they are often used. If you do not really know them by heart the answers all seem the same but of course there is only 1 correct answer.

Monitoring and logging is also an important piece of the exam so study this carefully.

It is very difficult to tell what subject have the most emphasis; I think that they change it every exam and maybe they test you more and more on 1 specific subject if the program detects that you give the wrong answers. So if you find yourself asking why so many questions are about the same subject I would recheck the other questions for that matter.

Nothing much to tell more so I wish everyone who's taking the exam good luck.