Here are some useful links I found on my travels.
Having never configured a Cisco device before I needed a lot of help understanding the commands, structure and syntax of the OS. It’s a hierarchical privilege model and commands often need to be chained together like a list of parameters. Takes a bit of getting used to, but it’s ok once you get it.
Useful Cisco config guide:
More useful cisco commands:
Beginner’s guide to Cisco IOS:
If you happen to start a netlab without a functioning configuration, this might help you out:
Network Fundamentals Pod configuration guide:
Here are a couple of subnet mask guides. One tries desperately to explain subnets without actually using any maths. Frankly, learn how to to do bitwise addition. It’s easier in the long run. The other calculated values based on what you enter. Useful.
Useful subnet calculation guide:
A subnet mask calculator: