HP-UX Reference (11i v3 07/02) - 4 File Formats (vol 8)

n
named.conf(4) named.conf(4)
(BIND 9.3)
An MX record must have an associated
A record; a CNAME is not sufficient. For a given domain, if there is
both a
CNAME record and an MX record, the
MX record is in error and will be ignored. Instead, the mail
will be delivered to the server specified in the
MX record pointed to by the CNAME.
Example
example.com. IN MX 10 mail.example.com.
IN MX 10 mail2.example.com.
IN MX 20 mail.backup.org.
mail.example.com. IN A 10.0.0.1
mail2.example.com. IN A 10.0.0.2
Mail delivery will be attempted to
mail.example.com
and mail2.example.com
(in any order), and
if neither of those succeed, delivery to
mail.backup.org
will be attempted.
SOA Resource Records
Each zone file begins with an
SOA record for the zone. All records in a zone file must be of the same class.
Described in RFC 1035.
Syntax
...
SOA mname rname serial refresh retry expire minimum
... The owner_name, ttl, and class have been omitted for clarity.
mname The domain name of the name server that is the source of data for this zone.
rname A domain name that specifies the mailbox of the person responsible for this zone. The first
period represents the @ in the e-mail address. If the mailbox user name contains a period,
you can escape it with a backslash (\). See the example.
serial An arbitrary unsigned 32-bit integer serial number for the zone. The range is 0 to
4294967295(2ˆ32-1).
refresh A 32-bit integer time interval in seconds to refresh the zone. See the Time Specification
section for more detail.
retry A 32-bit integer time to wait in seconds before retrying a failed refresh. See the Time
Specification section for more detail.
expire A 32-bit integer time interval in seconds after which the zone is no longer authoritative.
See the Time Specification section for more detail.
minimum The TTL in seconds for resolvers that cache negative responses. See the Time to Live
(TTL) and Time Specification sections for more detail.
The
SOA specifies a serial number, which should be changed each time the zone file is changed. Note that
it is not advisable to give the serial number as a dotted number, since the translation to normal integers is
via concatenation rather than multiplication and addition. You can represent the year, month, day of
month, and a 0..99 version number (yyyymmddvv) and still fit inside the unsigned 32-bit size of this field.
(It’s true that we will have to rethink this strategy in the year 4294.)
Secondary servers check the serial number at intervals specified by the refresh time in seconds; if the serial
number changes, a zone transfer will be done to load the new data. If a master server cannot be contacted
when a refresh is due, the retry time specifies the interval at which refreshes should be attempted. If a
master server cannot be contacted within the interval given by the expire time, all data from the zone is
discarded by secondary servers.
Example
@ IN SOA ucbvax.Berkeley.EDU. Jane\.Doe.ucbvax.Berkeley.EDU. (
1989020501 ; serial
10800 ; refresh
3600 ; retry
3600000 ; expire
86400 ) ; minimum
Time to Live (TTL)
The TTL field of an RR is a 32-bit integer representing time in seconds. It is primarily used by resolvers
when they cache RRs. The TTL describes how long a RR can be cached before it should be discarded. This
limit does not apply to authoritative data in zones; it is also timed out, but by the refreshing policies for the
266 Hewlett-Packard Company 34 HP-UX 11i Version 3: February 2007