Recommendations for Running BIND Page 5

If you still want to run BIND, the most recommended way to get it is via ISC. There are no other major versions of BIND like there are of Linux. ISC BIND is the only one in the eyes of many people.

BIND, as well as other DNS server packages, doesn’t just store translation information between domain names and IP address. (More can be found out about how DNS works here.) Aside from the “A” record, which translate a host name into an IP address, there are many other types of records in a DNS database. Below are a few, with a quick rundown of each, and their function.

• CNAME: CNAME is a pointer to another host. The use of the CNAME entry is very important if one wishes to refer to the same machine as mail.host.com, pop.host.com and even smtp.host.com. CNAME records generally point to a record defined by the “A” Record. An Entry looks like:

  Secondaryhost.domain.com. IN CNAME host.domain.com

• SOA (Start of Authority): This holds some administrative information about the domain records for which the server has some authority. It is a must-have for all DNS databases. This record also holds the time to live information for all records in its database.
• A: This is the record that makes everything possible. It is the record that actually maps the domain name to the IP address. An example entry would look something like:

  hostname.domain.com. IN A 192.168.0.2.

• MX (Mail Exchanger): If you want to offer e-mail, this is the record for you. MX defines which computer will act as the mail server for a certain domain. A sample entry would look like:

  Domain.com. 10 IN MX hostnameofmailserver.domain.com

  Domain.com is the name of the domain you wish to use for e-mail. Using this setup, the Webmaster’s e-mail address would be webmaster@Domain.com. The Webmaster would log in to check his or her e-mail by using hostnameofmailserver.domain.com as a POP and SMTP server. The number “10” signifies the priority of the mail server. This comes in handy for large systems that have a back-up e-mail server or two.

• PTR: Although PTR records can be used in many ways, they are most commonly used for reverse DNS look ups, also known as in-addr.arpa lookups. in-addr.arpa PTR records are the exact opposite of A records. The in-addr.arpa PTR record for the sample A record above would look like this:

  2.0.168.192.in-addr.arpa IN PRT hostname.domain.com.

  PTR in-addr.arpa records are used mainly for security issues, to verify that a computer actually is what it says it is.

• NS (Name Server): NS records simply identify the authoritative name server for a domain. There must be at least two of these records for every domain. A sample entry looks like:

  Domain.com. IN NS nameserver.whereever.com.