Panasonic Panafax DX-2000, Руководство по обслуживанию

Страница: 307 / 322

334
10.5.2. Primary Name Server
A primary server has the original copy of a zone file. Any changes made to the zone file are made to the copy on the primary
server. When a primary server receives a query about a host name in its own zone, it retrieves the host resolution locally from its
own zone files.
10.5.3 Secondary Name Server
A secondary server gets a copy of zone files from another server. This zone file is a read-only copy of the original file from the
primary server. Any changes made to the zone file are made at the primary server, then the changes are copied down to the
secondary server through a zone transfer. Multiple secondary servers in a domain improves performance.
10.5.4 SOA (Start of Authority) Record
Each database file starts with a Start of Authority (SOA) record for the file. This record specifies the zone’s primary server, the
server that maintains the read/write copy of the file. The syntax of this record is as follows:
IN SOA <source host><contact email><serial No.><refresh time><retry time><expiration time><TTL>
An example of the syntax is shown below:
The "@" symbol in this example indicates the local server; "IN" indicates an Internet record. The FQDN for the name server NWR18
must end in a period. Note that the email address for the administrator must have a period instead of the "@" symbol. Also, if the
SOA record is on more than one line, an open parenthesis must end the first line, and a close parenthesis must end the last line.
The following list explains the other parameters:
* Source host: The name of the host that has the read/write copy of the zone file.
* Contact email: The Internet email address of the person who maintains this file. This address must be expressed with a period
instead of the "@" that is usually found in email addresses (i.e. hostmaster.rdmg.mgcs.mei.co.jp instead of hostmas-
ter@rdmg.mgcs.mei.co.jp).
* Serial number: A version number for the zone file. This number should be changed each time the zone file changes, it changes
automatically if you use DNS Manager to change the zone file.
* Refresh time: The time, in seconds, that a secondary server waits before checking the master server for changes to the data-
base file. If the file has changed, the secondary server requests a zone transfer.
* Retry time: The time, in seconds, that a secondary server waits before trying again if a zone transfer fails.
* Expiration time: The time, in seconds, that a secondary server keeps trying to transfer a zone. After the expiration time passes,
the old zone information is deleted.
* TTL: The time, in seconds, that a server can cache resource records from this database file. The TTL is sent as part of the
response for any queries that are answered from this database file. An individual resource record can have a TT: that overrides this
value.
SOA Record (Bind 4.9.5 for NT) in "db.127.0.0" file
;
; File: db.127.0.0 file
; Purpose: This file establishes the identity of this DNS.
; SOA stands for 'start of authority' and sets the
; default parameters for information this DNS is
; authoritative for:
;
@ IN SOA nwr42.rdmg.mgcs.mei.co.jp. hostmaster.rdmg.mgcs.mei.co.jp. (
951213 ; serial number
43200
7200
1209600
172800)
;
IN NS nwr42.rdmg.mgcs.mei.co.jp.
1 IN PTR localhost.rdmg.mgcs.mei.co.jp.
;
; refresh every 12 hours
; retry after 2 hours
; expire after 2 weeks
; default ttl is 2 days