DNS...How, really?

[RhythmAddict]

Whats up everyone? I was reading this post and it got me to thinking about DNS and how it works...I've been doing site design for awhile and the most involved I've gotten w/DNS is setting up a domain to point to a certain nameserver, which seemed pretty straight/clear. So I have a couple of random questions concerning DNS...
1) Why set up a DNS server, at your company? For speed..? What else?
2) What is the deal with MX, A and PTR?
3) In simple terms, what is involved in setting up a DNS server?

Just curious, thank you everyone...I realize I could obtain all this info from the web, or a book - but you guys seem to explain things considerably better...thanks again

 

[chsh1ca]

Originally posted by: RhythmAddict
Whats up everyone? I was reading this post and it got me to thinking about DNS and how it works...I've been doing site design for awhile and the most involved I've gotten w/DNS is setting up a domain to point to a certain nameserver, which seemed pretty straight/clear. So I have a couple of random questions concerning DNS...
1) Why set up a DNS server, at your company? For speed..? What else?

Configurability, control, and time. If you need to add any new domain records, it doesn't involve contacting the domain hosts, it merely involves modifying the DNS server's configuration. Running your own authoritative nameserver has several other advantages as well, but primarily the accessibility of running your own server is the ideal reason to, among other things.

2) What is the deal with MX, A and PTR?

The MX record is the record that tells you what host(s) are mail exchangers (handle emails) for the domain. This is how mail servers know which host to send all emails destined for a particular domain name.
The A record is a simple host record, it specifies the hostname (ie: www, mail, ftp) and the IP address(es) mapped to that hostname.
The PTR record is a simple pointer. Let's say you used to have a second webserver at www2.yourdomain.com, but you removed it, and you need requests to that site to instead be served by the main webserver at www.yourdomain.com. To accomplish this, in your DNS record, you can just change the www2 entry from an A record to a PTR record, and give it www as its target. When a client does a lookup for www2, it will see that www2 is just a pointer for another host, and will then lookup the designated host (www), and connect that way. This system is designed to make domain host transitions easier.

3) In simple terms, what is involved in setting up a DNS server?

Specifics will vary by OS, but the fundamental steps are:
1. Get static IP block from your ISP.
2. Setup DNS server software.
3. Register domain, telling the registrar the public IP address of your DNS server.

 

[AKA]

1) Why set up a DNS server, at your company? For speed..? What else?

For control, speed, availabiliy, reliability, intranet, website etc.

If you have an intranet its obvious any external dns site wont resolve your private network.

2) What is the deal with MX, A and PTR?

MX is a mail record, use to add alternate location / backup mail server.

If an mx record of 5 to mail.anywhere.com is not available then it will try the next mx record 10 (example, lower # has higher priority) mail1.anywhere.com until an email server at one of the records is available and excepts the email.

If you only have one email server and have not setup anyone else for your email to spool to.. then you do not need an mx record, an A record pointing to your domain will suffice.

An A record is the actual IP address of the domain.

A PTR is a reverse record which associates an IP address with a canonical name.


DNS Glossary

3) In simple terms, what is involved in setting up a DNS server?

To setup an internet DNS server:

Register a domain name with a registar.
When registar ask for the nameservers that you want to use put in your static IP address of your intended dns server.
Then setup/install DNS software on your Operating System. Its included in win2k through add/remove windows components.
Then configure it for your domain.


Suggested requirements:

High speed always on connection
Static IP address
Router with ports 53 tcp/udp forwarded to server

 

[bluegreenturtle]

Ok, so here's a dumb comfirming question:

our company has an FTP server. We just switched ISP's. So I got a static IP for that server and registered the ftp.ourcompany.com as a PTR record to that IP. Was that the correct thing to do, or did I not even need to bother with a PTR? It works, though there was some sort of bobble yesterday with internal access.

 

[dexter333]

Originally posted by: bluegreenturtle
Ok, so here's a dumb comfirming question:

our company has an FTP server. We just switched ISP's. So I got a static IP for that server and registered the ftp.ourcompany.com as a PTR record to that IP. Was that the correct thing to do, or did I not even need to bother with a PTR? It works, though there was some sort of bobble yesterday with internal access.

Actually, you're going to want to set up an A record for ftp.yourcompany.com to the ftp server's ip.

 

[RhythmAddict]

Awesome. Thanks guys! (that'll be next weeks project..at home)