One skill that I really needed on the CCNP exams was to remember my subnetting skills. This was one skill that took me a while to develop. I found out about Paul Browning and his training system for CCNA. What really got my attention was his ability to cut through mess of dealing with 1’s and 0’s and subnetting to get you to where you can do some of the subnetting in your head. The system that I came to know from him involved a chart that he has readily available for download from his website – http://www.howtonetwork.net. Anybody I talk to I tell them about Paul’s website. When we first crossed paths, he was doing the CCNA track only. In checking his site recently, he has branched out a bit to including covering the CCNP R/S certification.
In interviewing several candidates at a previous employer for an architect or senior level position, I was shocked at the number of applicants that we talked to that couldnt answer the most basic of subnetting questions. I dont do this a lot but I try to keep fluent in subnetting. You never know when you may need to do it, so keeping your skills sharp is a good thing to do. When I took the CCNP Security (then CCSP) exams, I could count on one hand the number of questions I had that required some degree of subnetting skill. I wasnt surprised on each of the CCNP R/S exams to see the number of questions where you needed to subnet raised significantly. You can check out his subnetting oriented site at – http://www.subnetting-secrets.com. One of the tools he has is a bit of java code that will generate a series of questions to help you keep fluent and honest.