CISCO IOS in a Nutshell

Conventions

The following conventions are used in this book:

Italic

Used for filenames and URLs

Constant width

Used for commands, command keywords, and anything else that has to be typed literally

Constant width italic

Used for parameters or arguments that must be substituted into commands

Constant width bold

Used for user input in code

[ Keywords and other stuff ]

Used for optional keywords and arguments

{ choice-1 | choice-2 }

Used to signify either choice-1 or choice-2

Tip

This icon signifies a tip relating to the nearby text.

Warning

This icon signifies a warning relating to the nearby text.

One of the confusing things about working with a Cisco router is the notion of a command context . Most commands are legal only in limited situations; all of the quick-reference entries include a command context that indicates how the command is to be used. A context of “command” means that the command is for interactive use and is not entered into the router’s configuration; you do not need to enter the configuration mode (configure terminal) to give the command, and you can’t include it in a configuration file that you upload. A context of “global” indicates that a command doesn’t require any specific context; you can give it as soon as you’ve entered the configuration mode. A context of “interface” indicates that you must be in the interface configuration submode to give the command; “line” means that you must be in the line configuration submode, and so on.

IOS has no concept of a continuation character for breaking up command lines that are too long. That may be okay for a router, but it’s a problem for a book; still, I’ve decided not to invent a continuation character for the purposes of this book. I’ve split long commands across lines as it seemed most convenient and clear; just remember that you have to type it all on one line.