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September 10, 2006 1
IT 3653 – Client Server Systems Administration
Domains, DNS, and Dynamic DNS (Lecture 2)
Fall 2006, Feibish
September 10, 2006 2
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
September 10, 2006 3
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.
September 10, 2006 4
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."
September 10, 2006 5
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.
September 10, 2006 6
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.
September 10, 2006 7
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
September 10, 2006 8
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.
September 10, 2006 9
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.
September 10, 2006 10
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.
September 10, 2006 11
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."
September 10, 2006 12
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. "
September 10, 2006 13
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
September 10, 2006 14
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
September 10, 2006 15
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."
September 10, 2006 16
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.
September 10, 2006 17
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
September 10, 2006 19
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).
September 10, 2006 30
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"
September 10, 2006 35
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?
September 10, 2006 36
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."
September 10, 2006 37
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.