Thread: CNames and Name Servers

Can someone please explain to me what is the difference between the two? if there are any differences at all... I don't really seem to get how these alias and all that mean...

Ah, what fond memories this post brings up.

I've done some time in the hosting industry, and I stayed muddled over the alphabet soup of DNS records most of the time. The items and aspects of DNS are so relational and dependent that I always have trouble defining them separately, but here is some info I cobbled together from various resources - maybe it'll help.

From Domain Avenue:

A, Address Records

Address, or "A" records, map the name of a machine to its numeric IP address. In clearer terms, this record states the hostname and IP address of a certain machine. To "resolve" a hostname means to find its matching IP address. This is the record that A nameserver would send another name server to answer a resolution query. The record below is an example of how an A record should look:

eric.foobarbaz.com. IN A 36.36.1.6

The first column contains the machine's hostname. The second column lists what class the record is. For most basic DNS work, all you will need is the IN designation, which stands for Internet. The next column denotes the type of record the entry actually is, and the last column is the IP address itself. It is possible to map more than one IP address to a given hostname. This often happens for people who run a firewall and have two ethernet cards in one machine. All you must do is add a second A record, with every column the same save for the IP address. It is also possible to map more than one host name to one IP address. This is not recommended, however, since DNS has a special record for allowing machines to have aliases, called a canonical name, or CNAME record.

from Wikipedia and Domain Avenue:

A CNAME record or canonical name record is an alias of one name to another. There must always be an A record for the machine before aliases can be added. The host name of a machine that is stated in an A record is called the canonical, or official name of the machine. Other records should point to the canonical name. Here is an example of a CNAME:

www.foobarbaz.com. IN CNAME eric.foobarbaz.com.

Records always read from left to right, with the subject to be queried about on the left and the answer to the query on the right. A machine can have an unlimited number of CNAME aliases. A new record must be entered for each alias.
This is useful when running multiple services (like an FTP and a webserver) from a single IP address. Each service can then have its own entry in DNS (like ftp.example.com and www.example.com.)

from NameSecure:

The name server handles CNAME records in a different manner than aliases are handled in the host table. When a name server looks up a name and finds a CNAME record, it replaces the name with the canonical name and looks up the new name.

A Name Server is a computer that maps domain names (such as "mycompany.com") to IP addresses (such as "123.123.4.5"). For a domain name to be functional, it must be associated with at least one name server.

from Wikipedia:

An NS record or Name Server record maps a domain name to a list of DNS servers authoritative for that domain.

I find it's also helpful to try to understand the parts of a domain name as well when trying to make sense of all this. From Wikipedia:

A domain name usually consists of two or more parts (technically labels), separated by dots. For example wikipedia.org.

* The rightmost label conveys the top-level domain (for example, the address en.wikipedia.org has the top-level domain org).
* Each label to the left specifies a subdivision or subdomain of the domain above it. Note that "subdomain" expresses relative dependence, not absolute dependence: for example, wikipedia.org comprises a subdomain of the org domain, and en.wikipedia.org comprises a subdomain of the domain wikipedia.org. In theory, this subdivision can go down to 127 levels deep, and each label can contain up to 63 characters,[1] as long as the whole domain name does not exceed a total length of 255 characters. But in practice some domain registries have shorter limits than that.
* A hostname refers to a domain name that has one or more associated IP addresses. For example, the en.wikipedia.org and wikipedia.org domains are both hostnames, but the org domain is not.

The DNS consists of a hierarchical set of DNS servers. Each domain or subdomain has one or more authoritative DNS servers that publish information about that domain and the name servers of any domains "beneath" it. The hierarchy of authoritative DNS servers matches the hierarchy of domains. At the top of the hierarchy stand the root nameservers: the servers to query when looking up (resolving) a top-level domain name (TLD).

Name servers is tha actual server that tells where your domain is....

Someone looking for www.yoursite.com will hit the domains name servers which contain the entries (a, cname, etc) for where to point different types of requests.

The nameservers are what are listed on your domain registration which tell what DNS server the domain (yourdomain.com) is going to use.

A CNAME is a DNS record on the DNS server used for parked domains. A Parked domain is an additional domain that points to a main domain. For example, my site interactiveonline.com is the main domain. interaciveonline.net is parked to interactiveonline.com. In order to accomplish this a CNAME record was created for interaciveonline.net to point to interaciveonline.com

*That* made a whole lot of sense! I didn't have to pull out any jargon dictionary to understand that! Thanks davet, thanks a lot guys