A (Address) Record
An A record tells a DNS server what specific IP address to map for a host name. It is the most common type of DNS record. An A record is typically used to direct your domain name, for example www.yourname.com, to a web server.
Example A record format: 98.124.253.253
AAAA (IPv6 Address) Record
An AAAA (or "quad-A") record is similar to an A record, except that it maps a hostname to an IPv6 address. An A record specifies an IPv4 address, which is currently the dominant Internet Protocol version. In 1998 the IETF designated IPv6 as the successor to version 4 mainly for its much larger amount of available addresses, which provides flexibility in allocated addresses and routing traffic and prevents address exhaustion as more and more hosts are connecting to the Internet and available IPv4 addresses are running out.
IPv6 addresses are normally written as eight groups of four hexadecimal digits, where each group is separated by a colon.
Example IPv6 format: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
To shorted the writing and presentation of addresses, several simplifications to the notation are permitted.
Any leading zeros in a group may be omitted; thus, the example becomes: 2001:db8:85a3:0:0:8a2e:370:7334
One or any number of consecutive groups of 0 value may be replaced with two colons (::): 2001:db8:85a3::8a2e:370:7334
Optional section
This substitution with double-colon may be performed only once in an address, because multiple occurrences would lead to ambiguity. For example, the illegal address notation 2001::FFD3::57ab, could represent any of the following:
2001:0:0:0:0:FFD3:0:57ab
2001:0:0:0:FFD3:0:0:57ab
2001:0:0:FFD3:0:0:0:57ab
2001:0:FFD3:0:0:0:0:57ab
Using the double-colon reduction the localhost (loopback) address, fully written as 0000:0000:0000:0000:0000:0000:0000:0001, may be reduced to ::1 and the undetermined IPv6 address (zero value), i.e., all bits are zero, is simply ::.
For example, the addresses below are all valid and equivalent:
2001:0db8:0000:0000:0000:0000:1428:57ab
2001:0db8:0000:0000:0000::1428:57ab
2001:0db8:0:0:0:0:1428:57ab
2001:0db8:0:0::1428:57ab
2001:0db8::1428:57ab
2001:db8::1428:57ab
CNAME (Alias) Record
A CNAME (or Cononical Name) record tells DNS that this hostname is an alias of another domain name. This hostname then ends up resolving to the same IP address as the target domain name.
This helps if you manage multiple hostnames on the same or even different domain names that will allways point to the same IP address. If you specify all of these hostnames as CNAME records that point to one host with an A record, then if you need to update that IP address the master A record is all that needs to be updated, and all hostnames referring to it via a CNAME will automatically resolve to the new address.
Restrictions
A CNAME must have no other records of other types (MX, A, etc). This is very important especially with the @ record. If you specify a CNAME record type for the @ hostname, then email will not route properly for this domain name.
CNAME records that point to other CNAME records should be avoided. It is possible to create infinite loops and other error conditions.
Other DNS record types that point to other names, such as NS, MX, PTR, and SRV should never point to a CNAME.
Example CNAME record format: www CNAME www.myothername.com
URL Redirect record
URL Redirect is not a native DNS record type. Specifying URL Redirect for a hostname creates an underlying A record that directs the name to our URL Forwarding servers. These servers then perform an HTTP 301 redirect to the URL you specify in the address field. You can specify only the domain name to go to, or a full path to a specific file.
Example URL Redirect record formats:
www URL Redirect http://www.someotherdomainname.com/
blog URL Redirect http://weblogs.asp.net/pwilson/
Note that after redirecting, the target URL will show in the browser's URL text box.
If a user specifies a path or filename after the domain name when requesting a host that is URL Redirected, that path information is intelligently appended to the destination URL. In the example above, if a user had entered "www.myname.com/someotherpage.html" in a browser, this would redirect to "http://www.someotherdomainname.com/someotherpage.html".
TXT records were originally intended for human-readable text in a DNS record. This record type is now used as machine-readable data for several services, such as Opportunistic encryption, Sender Policy Framework (SPF), DomainKeys Identified Email (DKIM), DNS-SD, etc.Our system will accept any text in the address field of a TXT record. If you are setting up a data string intended for use with a specific service, such as SPF, you should use a utility to generate a string for you so there are no errors (for example www.openspf.org has an SPF builder tool).
