september 10, 2006 1 it 3653 – client server systems administration domains, dns, and dynamic dns...

September 10, 2006 1

IT 3653 – Client Server Systems Administration

Domains, DNS, and Dynamic DNS (Lecture 2)

Fall 2006, Feibish


So, how do I get "on the Internet"?

1. Register a domain name.

2. Obtain a static or dynamic IP address

3. Choose and implement DNS service to link the domain name to IP address.

4. Choose the desired services which you will run on the server.

5. Configure firewall/router with port forwarding


How do domain names work?http://help.godaddy.com/article.php?article_id=327&topic_id=161&&

A domain name works like an address forwarding service.

All of your Web site content sits on a computer with a unique address.

This is called an IP address. An IP address is made up of a series of numbers, such as 123.23.234.45.

Your domain name directs visitors to your site using this IP address.

We use domain names instead of IP addresses because most people find it easier to remember a name rather than a series of numbers.


What Is a Domain Name?http://help.godaddy.com/article.php?article_id=1497&topic_id=161&&

"A domain name is a Web, email, or other server address." (Not quite – let's work on this def)

The domain name is mapped (using DNS) to an IP address (which represents a physical point on the Internet).

When someone types a domain name into a Web browser, the requested Web page will open.

For example, the domain name www.yourpersonaldomain.com locates an Internet address for "yourpersonaldomain.com."


What Is a Domain Name? http://help.godaddy.com/article.php?article_id=1497&topic_id=161&&

consists of a top-level and a second-level domain. The "com" part of the domain name reflects the

purpose of the organization or entity and is called the top-level domain (TLD) name.

The second-level domain name—being the "readable" part of the address—thus refers to the organization or entity behind the Internet address.

Second-level domain names must be unique on the Internet and registered with an Internet Corporation for Assigned Names and Numbers (ICANN)-accredited registrar.


What is DNS?http://www.dyndns.com/support/kb/archives/what_is_dns.html

The Domain Name System or Service (DNS) is a process that maps hostnames (how humans address servers) to IP addresses (how computers address servers).

When you visted www.dyndns.org, your computer resolved that hostname as 63.208.196.100.

This translation happens every time you access a website, FTP server, or your e-mail.


What is: Domain Registrationhttp://www.dyndns.com/support/kb/archives/what_is_dns.html

The virtual real estate - Purchasing a domain gives you a lease to a domain name from a domain registry like .com, .net, or .org. The domain registrar allows you to specify nameservers for that domain.

Examples of Domain Registrars: Network Solutions godaddy.com dyndns.org


What is: DNShttp://www.dyndns.com/support/kb/archives/what_is_dns.html

The glue - When someone types in a domain name like 'dyndns.com', a process called the domain name system (DNS) works to turn that name into a number called an IP address.

Computer hardware uses numbers (addresses), but humans prefer names.

A number is ultimately required to access a service or resource.


What is: The network service?http://www.dyndns.com/support/kb/archives/what_is_dns.html

The content - After the DNS is resolved, the client will access the service at the given IP address and return a webpage in this case.

DNS is a required "glue" for any Internet application or service where you use a hostname or domain name.


Dynamic DNS

Appropriate if your IP address changes

if you have a dynamic IP address A client on your PC or router updates the DNS

servers with updated information

Vendors Dyndns.org NO-IP.com etc.


Dynamic DNShttp://www.dyndns.com/services/dns/dyndns/

"The free Dynamic DNS service allows you to alias a dynamic IP address to a static hostname in any of the many domains we offer, allowing your computer to be more easily accessed from various locations on the Internet.

We provide this service, for up to five (5) hostnames, free to the Internet community."


Dynamic DNS, from dyndns.orghttp://www.dyndns.com/services/dns/dyndns/

"The Dynamic DNS service is ideal for a home website, file server, or just to keep a pointer back to your home PC so you can access those important documents while you're at work."

"Using one of the available third-party update clients you can keep your hostname always pointing to your IP address, no matter how often your ISP changes it.

No more fumbling to find that piece of paper where you wrote down your IP address, or e-mailing all your friends every time it changes. "


Features in Dynamic DNS®http://www.dyndns.com/services/dns/dyndns/

Hostnames in 68 domains Wildcarding, allowing *.yourhost.dyndns.org to point

to yourhost.dyndns.org Offline URL redirection MX records, allowing for flexible e-mail configurations Clients for a wide variety of platforms An open, non-proprietary update interface Almost instantaneous DNS propagation time Free, industry leading e-mail support 5 DNS servers in 4 redundant tier-1 datacenters

around the globe


Dynamic DNSSM Domainshttp://www.dyndns.com/services/dns/dyndns/

ath.cx

blogdns.com

blogdns.net

blogdns.org

boldlygoingnowhere.org

dnsalias.com

dnsalias.net

dnsalias.org

dnsdojo.com

dnsdojo.net

dnsdojo.org

dvrdns.org

dyn-o-saur.com

dynalias.com

dynalias.net

dynalias.org

dyndns.biz

dyndns.info

dyndns.org

dyndns.tv

dyndns.ws

ftpaccess.cc

game-host.org

game-server.cc

getmyip.com

gotdns.com

gotdns.org

ham-radio-op.net

hobby-site.com

homedns.org

homeftp.net

homeftp.org

homeip.net

homelinux.com

homelinux.net

homelinux.org

homeunix.com

homeunix.net

homeunix.org

is-a-chef.com

is-a-chef.net

is-a-chef.org

is-a-geek.com

is-a-geek.net

is-a-geek.org

isa-geek.com

isa-geek.net

isa-geek.org

kicks-ass.net

kicks-ass.org

merseine.nu

mine.nu

myphotos.cc

podzone.net

podzone.org

scrapping.cc

selfip.biz

selfip.com

selfip.info

selfip.net

selfip.org

servebbs.com

servebbs.net

servebbs.org

serveftp.net

serveftp.org

servegame.org

shacknet.nu


DynDNS Custom DNS Servicehttp://www.dyndns.com/services/dns/custom/

"DynDNS' Custom DNS service provides a managed primary DNS solution, giving you complete control over an entire domain name and providing a unified primary/secondary DNS service.

A web-based interface provides two levels of control over your domain, catering to average or power users."


DynDNS Custom DNS Servicehttp://www.dyndns.com/services/dns/custom/

"With DynDNS' Custom DNS service you can make changes to your DNS from anywhere at any time and be assured that your changes will propagate to the rest of the internet in a matter of minutes.

This service supports dynamic and static IP addresses.


DynDNS Custom DNS Featureshttp://www.dyndns.com/services/dns/custom/

Support for any domains purchased from DynDNS Support for almost every top level domain (TLD) name, including yourname.com,

yourname.co.uk, etc. Ability to update IP addresses dynamically using any Custom DNS-aware client Ability to configure various subdomains (sub1.domain.com, sub2.domain.com) and have

them pointing to the same IP address or to different IP addresses Ability to create unlimited A records (hosts) Ability to create unlimited CNAME records (aliases) Ability to create unlimited MX records (Mail eXchangers) of various priorities Ability to create unlimited TXT (text) records Included MyWebHop add-on provides HTTP redirection (redirecting www.yourdomain.com

to http://www.yourisp.com/~yourusername/) with optional cloaking Offline URL feature allows HTTP requests to your domain to be redirected to another site

when your server is offline Five DNS servers in four geographically-diverse locations to ensure that DNS resolution for

your domain never fails Easy to follow instructions and industry leading support (by e-mail or phone) A Service Level Agreement and 24x7x365 Premier Support are available for customers

who need to be absolutely certain their domain will always be available


Custom DNS – Config Example:


What if you have a dynamic IP address? DNS provider will provide a client, or your

router may include code to update the DNS service.

Client will detect changes to your public IP address and report the changes to the DNS provider (thereby updating your DNS records automatically).


Example: DynDNS client


DNS clients

This is an example of one client – there are many clients and providers to choose from

Can run on any host behind your firewall

Should only run on 1 host

Too many updates considered "abusive"


Example – Router Config Screen


DNS Router – vendor choices in firmware


Router config – Linksys


Linksys – vendor choices


Okay…

We have a domain name.

DNS has "glued" our domain name to our IP address

DNS client is updating our dynamic IP address, if necessary.

BUT how do we get traffic to the correct program/service?


Port Forwardinghttp://en.wikipedia.org/wiki/Port_forwarding

"Port forwarding (sometimes referred to as tunneling) is the act of forwarding a network port from one network node to another. This technique can allow an external user to reach a port on a private IP address (inside a LAN) from the outside via a NAT-enabled router."

"Port forwarding allows remote computers (e.g. public machines on the Internet) to connect to a specific computer within a private LAN."


Port Forwardinghttp://en.wikipedia.org/wiki/Port_forwarding

For example: forwarding port 8000 on the router to a user's machine

allows SHOUTcast streaming forwarding ports 5000 through 6000 to a user's

machine allows the use of Unreal Tournament

Modern Linux machines achieve this by adding iptables rules to the nat table: with target DNAT to the PREROUTING chain, and/or with target SNAT in the POSTROUTING chain.


Checking if ports are openhttp://www.canyouseeme.org/


DlinkExample


Port Forwarding - Linksys


Port Forwarding – LinksysService Configuration


Questions?

september 10, 2006 1 it 3653 – client server systems administration domains, dns, and dynamic dns...

Documents

domain registry

level domain names

domain registration

domain names work

level domain namebeing

internet address

toplevel domain tld

examples of domain registrars