Originally, when I wanted to take a Juniper exam, I wanted to tackle the JNCIS-SEC, cause 95% of my time is spent on SRX's and other security areas, and I'd say the other 5% on EX switches and M series routers. I learned, however, that you can't just run before you learn how to walk, so I had to take the JNCIA-Junos exam first, which is a prerequisite to the JNCIS line of exams.
I started by going back over some of the training manuals I had from a couple of years ago when I took aJNCIS Enterprise Switching and Routing course. This course was condensed into a week, in a "bootcamp" type format, and included the following classes:
Introduction to the Junos Operating System
Junos Routing Essentials
Junos Intermediate Routing
Junos Enterprise Switching
The first few study days were spent on the information that deals with the JNCIA-Junos exam, so it was a good place to start. I followed that by taking a couple of the practice exams on Juniper's website to see what areas I needed to focus on when dealing with the JNCIA-Junos exam:
Because I have had a lot of experience in this field, and have been doing it for quite some time, I really didn't need to bother with the Network Fundamentals test. However, it was a really well layed out and designed course, and I recommend anyone new to the field to definitely take a look at it.
I already had a feeling about one area I needed to focus more time/learning on...and that is CoS (Class of Service, or QoS to some).
I did pretty well on the practice exams, as I had a feeling I would. It definitely helps having the experience over the past few years of working hands on with the products versus coming in blind and just basically reading about them and then taking the test. So this experience was a little different for me than others who might be just getting into Juniper/Junos. I decided to focus mainly on CoS, since that was one of my weaker areas as I don't really deal with it too much now. We are going to be using it more and more as the year goes on, so it is only going to help.
Once I spent a few days reading up on CoS, from the training manuals I had from the JNCIS bootcamp, as well as browsing some of the documentation on Juniper's website, I went ahead and scheduled my exam a week out, and then tried to just brush up on anything that I felt I didn't quite feel 100% about going into it (which wasn't too much). Fast-forward to exam day, and I felt really confident going into it. I scheduled it for the AM, as I wanted to get it done and out of the way versus sitting and maybe over thinking things throughout the day, wondering if I had studied enough, etc.
I passed with a score over 90%, and I was really proud. It had been a while since I've had a certification, and it just felt good to get one again. Now, I plan on going after the security specialist one (JNCIS-SEC) later this year.
Other Great Resources
Another fellow Juniper Ambassador (Steve Puluka) posted his advice and experiences dealing with Juniper certifications, and I think this is something you all should definitely check out!