Configuring and Managing MPE/iX Internet Services (August 2002)

Chapter 8
DNS BIND/iX
Data Files
125
; Define localhost
;
localhost IN A 127.0.0.1
; Set up hosts
;
maxx IN A 204.251.17.241
IN MX 5 nova.maxx.net.
maxx.net. IN MX 5 nova.maxx.net.
;
; All mail for net delivered to nova
;
;* IN MX 10 nova.maxx.net.
www IN CNAME nova.maxx.net.
ftp IN CNAME nova.maxx.net.
news IN CNAME nova.maxx.net.
mail IN CNAME nova.maxx.net.
ns IN CNAME nova.maxx.net.
loghost IN CNAME nova.maxx.net.
lucy IN A 204.251.17.242
linux IN CNAME lucy.maxx.net.
lucy IN MX 10 lucy.maxx.net.
messdos IN A 204.251.17.243
messdos IN MX 10 messdos.maxx.net.
pentium IN CNAME messdos.maxx.net.
solaris IN A 204.251.17.244
solaris IN MX 10 solaris.maxx.net.
maxx4 IN CNAME solaris.maxx.net.
maxx5 IN A 204.251.17.245
maxx5 IN MX 10 maxx5.maxx.net.
maxx6 IN A 204.251.17.246
maxx6 IN MX 10 maxx6.maxx.net.
Most database file entries are known as DNS resource records. Generally, the resource records are shown in
order: SOA, NS, followed by the other types, but this ordering isn’t required. The data in each entry may be
entered in upper, lower, or mixed case. All entries in the database file must start at the beginning of the line.
Blank lines as well as any text following a semicolon is ignored.
SOA stands for Start of Authority. This acronym notifies named that operational parameters follow. The most
important one is the Serial field. Every time you make a change to a database file, you must increment its
serial number. Only by doing this will secondary servers know they need to reach into your system and pull
out new name server data, a procedure known as a “zone transfer.” Many DNS administrators use a date-time
stamp for this field, like 9602171 for the first version on February 17, 1996.
First, focus on the SOA section:
maxx.net. IN SOA nova.maxx.net. tyager.maxx.maxx.net.
The “maxx.net.” field tells named the domain defined by this file. The name server will automatically append
it to any host name that appears in the file. The trailing dot is not a type; it keeps named from trying to tack
on your domain name. Without it, the resolver would be confused by named’s expansion of my domain name
to “maxx.net.maxx.net.”
The IN stands for the “Internet” class of data. Even though other classes exist, they aren’t in common usage.
The “nova.maxx.net” field is the host on which these database files reside. Finally, “tyager.nova.maxx.net”
represents the e-mail address of the DNS administrator, where the first dot (between tyager and nova) would
be replaced by the @ symbol to create a valid address. (The @ symbol can’t be used here because it has a
reserved meaning in DNS database files.)
The open parenthesis at the end of the line allows you to split the SOA record across physical lines for
readability:
9602171 ; Serial