Bind 9 Administrator Reference Manual

Chapter 6. BIND 9 Configuration Reference
will get a distance which is further than any non-negated list element, and closer than any negated
element.
Because of the first-match aspect of the algorithm, an element that defines a subset of another element in
the list should come before the broader element, regardless of whether either is negated. For example, in
1.2.3/24; ! 1.2.3.13; the 1.2.3.13 element is completely useless because the algorithm will match any
lookup for 1.2.3.13 to the 1.2.3/24 element. Using ! 1.2.3.13; 1.2.3/24 fixes that problem by having
1.2.3.13 blocked by the negation but all other 1.2.3.* hosts fall through.
6.1.2. Comment Syntax
The BIND 9 comment syntax allows for comments to appear anywhere that white space may appear in a
BIND configuration file. To appeal to programmers of all kinds, they can be written in C, C++, or
shell/perl constructs.
6.1.2.1. Syntax
/* This is a BIND comment as in C */
// This is a BIND comment as in C++
# This is a BIND comment as in common UNIX shells and perl
6.1.2.2. Definition and Usage
Comments may appear anywhere that whitespace may appear in a BIND configuration file.
C-style comments start with the two characters /* (slash, star) and end with */ (star, slash). Because they
are completely delimited with these characters, they can be used to comment only a portion of a line or
to span multiple lines.
C-style comments cannot be nested. For example, the following is not valid because the entire comment
ends with the first */:
/* This is the start of a comment.
This is still part of the comment.
/* This is an incorrect attempt at nesting a comment. */
This is no longer in any comment. */
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