Looks like the recommendation from the most of people I asked is to skip the very first labs and jump on 26-35 (the version 4),however, still the very first labs are great in terms of building strong knowledge on things like redistribution,route filtering and troubleshooting. I am about to finish lab 7 and jump to lab 26.
source http://evilrouters.net/2011/01/18/cisco-iou-faq/ What is IOU? From the Cisco Engineering Education web site (a long time ago): IOS on Unix (IOU) is a fully working version of IOS that runs as a user mode UNIX (Solaris) process. IOU is built as a native Solaris image and run just like any other program. IOU supports all platform independent protocols and features. What operating systems does IOU run on? It is my understanding that, initially, IOU was Solaris (SPARC) only. Nowadays, however, there are also builds for OS X and Linux. Similar to dynamips, IOU allows you to build out a network topology on a computer, without the need for physical routers. This is useful for validating designs, proof-of-concept testing, and certification self-study. Is my system compatible with IOU? You will need to be running the operating system that your IOU image were built for, obviously. Other than that, there are no special requirements to run IOU. It is not very CPU- or memory-intensive, unlik...