This is the form that allows you to add DNS records of various types as well as edit existing records.

An “A” record is the most common type of record. It is the association of a name to an IP address. Each host you create using the Edit Host form will automatically create an A record and a PTR record.

Host Name and Domain

To start out with you will be asked for a Host Name and a Domain. These two fields together will build what is called a Fully Qualified DNS Name, or FQDN. In general the “host” portion of an FQDN is everything up to the first dot. The domain is the remainder of the FQDN. So for example in the FQDN: hostname.example.com.

There is more to discuss here as well as referencing better DNS tutorials and RFCs

TTL

The TTL setting tells the DNS server how long to cache this entry. When you create a domain, there will be a default domain wide TTL setting. Each record you add will use the domain level setting unless you click the “override” link and specify a new TTL value in seconds. It is pretty rare that you would need to change this to something other than what the domain itself uses.

IP Address

This will be the IP address that the FQDN will point to. This IP address must be an existing IP interface in the system. Typing in an address here that does not already exist will result in an error.

Auto Create PTR

This option is on by default and will automatically create the reverse pointer record (PTR) for this name and IP address pair. There are certain cases where you may not want to have a reverse IP address for a name but in general it is best to leave this box checked.

The cases where you may not want to have a PTR could be where you are adding a “service” name like ftp.example.com. In the normal case you might have server.example.com → 10.1.1.1 but you also want to refer to that IP using ftp.example.com. BUT when you do an nslookup 10.1.1.1 you want it to come back with server.example.com only and not both names. This is when you would uncheck the box.

Notes

Yep, they are notes. Use them wisely

Suggested records

AT the bottom there will be an updating string of text in green letters. This is printed out as you fill out the form to try and give you an example of how the DNS configuration might look in a BIND style configuration file. It is for reference only.

Keep adding more

Checking this box will keep the edit window open after you hit Save. It will also not blank out the form. This is nice for when you are adding multiple records with similar data. You would then only need to change an IP offset and hostname entry without filling out the rest of the info again.

A CNAME or Alias, as it is sometimes called, is a way to have one name refer, or point to, another name. This causes a second DNS lookup on the client when you use these but can be handy at times. As http://cr.yp.to/djbdns/tinydns-data.html you may want to use A records instead. I’ve used exclusively CNAMES before and been ok with it but he has a good point.

Existing A record

The only difference in this record type from the A record is that you must point it to an existing name in the system as opposed to an existing IP address in the system. The rest of the fields work the same.

MX records are for mail

MX Preference

MX records allow for a preference setting that lets you contol the order in which mail clients talk to the mail servers listed in the MX record. Place a numerical value here to set the preference.

The other fields are the same as the previous record descriptions.

TXT value

This is the string that would be returned when you look up the provided name.

The other fields are the same as the previous record descriptions.