Conventions

In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

There are three styles for code. Code words in text are shown as follows: "To limit upload, we will mark packets in the PREROUTING chain of the mangle table".

A block of code will be set as follows:

#Drop SSH packets except from admins
$IPT -A INPUT -s ! 1.2.3.16/28 -p tcp --dport 22 -j DROP

When we wish to draw your attention to a particular part of a code block, the relevant lines or items will be made bold:

tc filter add dev eth0 protocol ip parent 1:0 prio 5 u32 match ip src 1.2.3.34 flowid 1:100

New terms and important words are introduced in a bold-type font. Words that you see on the screen, in menus or dialog boxes for example, appear in our text like this: "In the IP: Netfilter Configuration section you will find the options needed for NAT".