mail us  |  mail this page

contact us
training  | 
tech stuff  | 

$ORIGIN, @ and blank Substitution

The symbol @ is used in BIND to denote zone root (which is sometimes also called the zone apex. The value substituted for @ is either:

Blank Substitution

Blank labels are a little messy and the substitution here is the last valid name (or label) or $ORIGIN if there are no previous names (labels). To illustrate blank name substitution:

; example.com zone file fragment 
; no ORIGIN directive
@   IN  SOA  ns1.example.com. hostmaster.example.com. (
                2003080800 ; se = serial number
                172800     ; ref = refresh = 2d
                900        ; ret = update retry = 15m
                1209600    ; ex = expiry = 2w
                3600       ; min = minimum = 1h
                )
....
    IN      NS     ns1.example.com. 
; the blank label in the NS substitutes example.com.
; Confusingly the whole definition could use blank substitution 
; as shown below which is functionally equivalent to above
; example.com zone file fragment 
; no ORIGIN directive
    IN    SOA   ns1.example.com. hostmaster.example.com. (
                  2003080800 ; se = serial number
                  172800     ; ref = refresh = 2d
                  900        ; ret = update retry = 15m
                  1209600    ; ex = expiry = 2w
                  3600       ; min = minimum = 1h
                  )
....
    IN    NS     ns1.example.com. 

Finally, to illustrate other uses of blank substitution see the following:

; zone file fragment for example.com.
...
; following two A RRs both have a label of www.example.com.
www   IN  A 192.168.2.3
      IN  A 192.168.2.4
; this could have also been written as shown if less confusing
www   IN  A 192.168.2.3
www   IN  A 192.168.2.4


Problems, comments, suggestions, corrections (including broken links) or something to add? Please take the time from a busy life to 'mail us' (at top of screen), the webmaster (below) or info-support at zytrax. You will have a warm inner glow for the rest of the day.

Pro DNS and BIND by Ron Aitchison

Contents

tech info
guides home
dns articles
intro
contents
1 objectives
big picture
2 concepts
3 reverse map
4 dns types
quickstart
5 install bind
6 samples
reference
7 named.conf
8 zone records
operations
9 howtos
10 tools
11 trouble
programming
12 bind api's
security
13 dns security
bits & bytes
15 messages
resources
notes & tips
registration FAQ
dns resources
dns rfcs
change log

Creative Commons License
This work is licensed under a Creative Commons License.

If you are happy it's OK - but your browser is giving a less than optimal experience on our site. You could, at no charge, upgrade to a W3C STANDARDS COMPLIANT browser such as Firefox

Search

web zytrax.com

Share

share page via facebook tweet this page

Page

email us Send to a friend feature print this page Decrease font size Increase font size Display full width page

Resources

Systems

FreeBSD
NetBSD
OpenBSD
DragonFlyBSD
Linux.org
Debian Linux

Software

LibreOffice
OpenOffice
Mozilla
GitHub
GNU-Free SW Foundation
get-dns

Organizations

Open Source Initiative
Creative Commons

Misc.

Ibiblio - Library
Open Book Project
Open Directory
Wikipedia

Site

CSS Technology SPF Record Conformant Domain
Copyright © 1994 - 2017 ZyTrax, Inc.
All rights reserved. Legal and Privacy
site by zytrax
Hosted by super.net.sg
web-master at zytrax
Page modified: October 21 2015.