DNS Administration (Reference)

This chapter covers the following topics.

• Implementing DNS: A Practical Example

• Setting Up the Data Files

• Setting Up Subdomains

• The DNS Namespace Hierarchy

• How DNS Affects Mail Delivery

• DNS Configuration and Data Files

• Data File Resource Record Format

Implementing DNS: A Practical Example

This section shows the files you need to implement DNS for a sample Internet-connected network, based on the examples used in this chapter.

Caution - The IP addresses and network numbers used in examples and code samples in this manual are for illustration purposes only. Do not use them as shown because they might have been assigned to an actual network or host.

This example assumes the following.

• An environment connected to the Internet

• Two networks, each with its own domain (doc.com and sales.doc.com) and its own DNS zone

• The doc.com domain and zone is the top zone over the sales.doc.com subdomain and zone

• Each network has its own network number

  Table 5-1 Example Network Domain and Zone Configuration

  Name and Zone	Number
  doc.com	123.45.6
  sales.doc.com	111.22.3

• Each zone has a master and one slave server, and the slave server of sales.doc.com is also the master server of doc.com

  Table 5-2 Example Network DNS Servers

  Zone	Host Name	Function	Address	CNAME
  doc.com	sirius	master for doc.com	123.45.6.1	dnsmaster
  doc.com	deneb	slave for doc.com	111.22.3.5	dnssecond
  sales.doc.com	altair	master for sales.doc.com	111.22.3.4	dnssales
  sales.doc.com	altair	slave for sales.doc.com	123.45.6.1	dnsmaster

Example Configuration Files

The following code examples show configuration files for the three servers in the two networks.

Example 5-1 Example Configuration File for dnsmastr Name Server

;
; Sample named.conf file on dnsmastr (sirius) name server
; 
; global options and defaults
;

options {
        directory  "/var/named";
};

; master zone definitions
;
zone "doc.com"  in  {
        type master;
        file "db.doc.com";
};

zone "6.45.123.in-addr.arpa"  in  {
        type master;
        file "db.123.45.6";
};

zone "0.0.127.in-addr.arpa"  in  {
        type master;
        file "db.127.0.0";
};

; slave server definitions
;
zone "sales.doc.com"  in  {
        type slave;
        file "tmp.db.sales";
        masters { 111.22.3.4; };
};

zone "3.22.111.in-addr.arpa"  in  {
        type slave;
        file "tmp.db.111.22.3";
        masters { 111.22.3.4; };
};

; root hints

zone "."  in  {
        type hint;	
        file "named.ca";
};
 

Example 5-2 Example Configuration File for dnssales Name Server

; 
; Sample named.conf file on the dnssales (altair) name server
; 

options {
        directory  "/var/named";
};

zone "sales.doc.com"  in  {
        type master;
        file "db.sales.doc.com";
};

zone "3.22.111.in-addr.arpa"  in  {
        type master;
        file "db.111.22.3";
};

zone "0.0.127.in-addr.arpa"  in  {
        type master;
        file "db.127.0.0";
};

; root hints

zone "."  in  {
        type hint;
        file "named.ca";
};