Page 129 - DCAP602_NETWORK_OPERATING_SYSTEMS_I

Unit 6: Domain Name System

as this will provide some redundancy if your server ever goes down. You’ll also want to modify notes
the /etc/resolv.conf file on the DNS server itself so that it points to itself. Do that by opening the
file in a text editor with the command:

nano /etc/resolv.conf
and making sure the first nameserver line is:
nameserver 127.0.0.1
Why is setting up a easy DNS server so easy? Because of things called “root hints”. The root hints
are a list of root-level DNS servers in the /etc/bind/db.root file. Your simple DNS server will
query a root server to get the addresses of authoritative DNS servers for each given domain (so it
can contact those authoritative DNS servers to get the IP addresses of the desired hosts).
Just keep in mind that your simple DNS server needs a 24/7 connection to the Internet. Or it at
least needs to be connected to the Internet any time any system on your LAN needs to access
anything on the Internet.

6.1.7 Dns server functions

You can set up a DNS server for several different reasons:
1. Internet Domain Support: If you have a domain name and you’re operating Web, e-mail,
FTP, or other Internet servers, you’ll use a DNS server ro respond to resolution question
so others can find and access your server(s). This is a serious undertaking and you’d have
to set up a minimum of two of them. On this page we’ll refer to these types of DNS servers
as authoritative DNS servers for reasons you’ll see later. However, there are alternatives to
having your own authoritative DNS server if you have (or want to have) your DNS records
for you. Even if someone else is taking care of your domain’s DNS records you could still
set up one of the following your own domain name. You can have someone else host types
of DNS servers.
2. Local Name Resolution: Related to the above scenario, this type of DNS server would
resolve the hostnames of systems on your LAN. Typically in this scenario there is one DNS
server and it does both jobs. The first being that it receives queries from workstations and
the second being that it serves as the authoritative source for the responses (this will be
more clear as we progress). Having this type of DNS server would eliminate the need to
have (and manually update) a HOSTS file on each system on your LAN. On this page we’ll
refer to these as LAN DNS servers.
During the Debian installation you are asked to supply a domain name. This is an internal
(private) domain name which is not noticeable to the outside world so, like the private IP
address ranges you use on a LAN, it doesn’t have to be registered with anyone. A LAN
DNS server would be authoritative for this internal, private domain. For security reasons,
the name for this internal domain should not be the same as any public domain name you
have registered. Private domain names are not restricted to using one of the established
public TLD (Top Level Domain) names such as .com or .net. You could use .corp or .inc or
something else for your TLD. Since a single DNS server can be authoritative for multiple
domains, you could use the same DNS server for both your public and private domains.
However, the server would need to be accessible from both the Internet and the LAN so
you’d need to locate it in a DMZ. Though you want to use different public and private
domain names, you can use the same name for the second-level domain.

Example: My-domain.com for the public name and my-domain.inc for the private
name.

LoveLy professionaL university 123