SOA Record

Select Certification Bootcamp :
MCSE MCSE+Security CCNA CCNP RHCE Register Course Fees Home

Leading MCSE, CCNA, CCNP Certification boot camp training provider in India, USA, UK.

SOA Record

Each database file starts with an SOA record, stating the start of authority for the file. This record specifies the primary server for this zone—the server that maintains the read/write copy of this file. The syntax of this record follows:

IN SOA <source host><contact e-mail><ser. No.><refresh time><retry time><expiration time><TTL>

An example of the syntax follows:

@ IN SOA ns1.erudite.com kwolford.erudite.com. (
101 ; serial number
10800 ; refresh [3 hours]
3600 ; retry [1 hour]
604800 ; expire [7 days]
86400 ) ; time to live [1 day]

The “@” symbol in this example indicates the local server; “IN” indicates an Internet record. The fully qualified name for the name server NS1 must end in a period. Note that the e-mail name for the administrator must have a period instead of the “@” symbol in the e-mail address. 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 with the read/write copy of the file.
Contact e-mail. The Internet e-mail address of the person who maintains this file. This address must be expressed with a period instead of the “@” that is usually found in e-mail addresses, such as kwolford.erudite.com instead of kwolford@erudite.com.
Serial number. The version number of the database. This number should be changed each time the database changes. This number changes automatically if you use DNS Manager to change the zone file. If you use a text editor to modify the zone file, you must change this number yourself.
Refresh time. The time a secondary server waits before checking the master server for changes to the database file. If the file has changed, the secondary server requests a zone transfer. This value is expressed in seconds.
Retry time. The time a secondary server waits before trying again if a zone transfer fails. This value is expressed in seconds.
Expiration time. The time a secondary server keeps trying to transfer a zone. After the expiration time passes, the old zone information is deleted. This value is expressed in seconds.
Time to live. The time a server can cache resource records from this database file. The time to live is sent as part of the response for any queries that are answered from this database file. An individual resource record can have a TTL that overrides this value. This value is expressed in seconds.

If a resource record uses more than one line in a database file, you must end the first line with an open parenthesis and the last line with a close parenthesis.

Figure 12.7 shows the dialog box used in DNS Manager to modify the SOA record.

Vibrant Advantage :

No Prestudy
Longest Duration Camp
Chalk Talk Training
Highest Passing Rate
Bootcamp since 1999
Guaranteed Certification ...

Testimonials :

MCSE Certification boot camp

The instructor taught real world experience and did not just teach us to pass the test. He knew the subject well and was encouraging. His lectures were very well delivered....

Colver Dennis, USA