Studying and practicing for your JNCIE examination means that you have a couple of conflicting things you need to work on. You need to practice for your speed of execution, but you also need to practice looking at outputs and developing your intuitive sense of where to look for problems when your protocols aren’t coming up or traffic is not flowing.
It can be hard to imagine the many different ways a protocol can break but the good news is you have an ally in this department: your lousy memory and your bad typing skills! :)
When I was sitting for my exam yesterday, I was missing a bit of configuration for a VPN I was configuring and the output was really a bit mystifying. It took me a while to sort it out. And it occurred to me that a person could really use their configuration mistakes to their own advantage while doing practice runs by patiently troubleshooting them without reaching for the books and looking things up right away.
So here’s the strategy I came up with:
Pick a technology you want to work on from the Exam Objectives. The more convoluted the better. Try to find ways to “tie one hand behind your back”, for instance by adding a restriction like VPN route-reflectors that don’t have MPLS running, or IGP total stub areas that require an aggregate route.
Configure the scenario as quickly as you can with as little configuration as possible. Don’t make mistakes on purpose but do rush it. Test with pings from the CE devices (end-to-end) if possible.
Assuming everything didn’t come up, start troubleshooting and really linger over the show commands. Do this especially when you have just found the problem looking at the before and after and seeing how the outputs are different.
Assuming everything did come up. You can still try to break it by removing an ingredient and comparing what the outputs look like while it is broken. (e.g. remove an interface from “protocols mpls” or remove an address family from the interface).
Make notes to yourself on what you learned in Evernote.
This will let you practice implementing things with speed while making an opportunity to practice spotting problems in your outputs when the network has missing or invalid configs.
photo credit: wifebot