Page 107 - DCAP602_NETWORK_OPERATING_SYSTEMS_I

Unit 6: Domain Name System

When to use a DNS Caching Name Server? notes

Most servers don’t ask authoritative servers for DNS directly, they generally ask a caching DNS
server to do it on their behalf. These servers, through a process called recursion, sequentially
query the authoritative servers at the root, main domain and sub domain levels to get eventually
get the specific information requested. The most frequently requested information is then stored
(or cached) to reduce the lookup overhead of subsequent queries.
If you want to promote your Web site www.my-site.com to the rest of the world, then a regular
DNS server is what you require.
After you set up your caching DNS server, you have to configure each of your home network PCs
to use it as their DNS server. If your home PCs get their IP addresses using DHCP, then you have
to configure your DHCP server to make it aware of the IP address of your new DNS server, so
that the DHCP server can advertise the DNS server to its PC clients. Off-the-shelf router/firewall
appliances used in most home networks usually can act as both the caching DNS and DHCP
server, rendering a separate DNS server is unnecessary.

Did u know? Is setting up a caching DNS server is fairly straightforward?

When to use a Static DNS Server?

If your ISP provides you with a fixed or static IP address, and you wish to host your own Web
site, then a regular authoritative DNS server would be the way to go. A caching DNS name
server is used as a reference only; regular name servers are used as the authoritative source of
information for your Web site’s domain.

How to get your own Domain?

Whether or not you use static or dynamic DNS, you need to register a domain.
Dynamic DNS providers regularly offer you a sub domain of their own site, such as my-site.
dnsprovider.com, in which you register your domain on their site.
If you choose to create your very own domain, such as my-site.com, you have to register with a
company focus in static DNS registration and then point your registration record to the intended
authoritative DNS for your domain. Popular domain registrars include VeriSign, Register Free,
and Yahoo.

If you want to use a dynamic DNS provider for your own domain, then you have to point your
registration record to the DNS servers of your dynamic DNS provider. We will discuss this
later.

Basic DNS Testing of DNS Resolution

As you know, DNS resolution maps a Fully Qualified Domain Name (FQDN), such as www.
Ignou.ac.in, to an IP address. This is also known as a forward lookup. The reverse is also true: By
performing a reverse lookup, DNS can determining the fully qualified domain name associated
with an IP address.
Many dissimilar Web sites can map to a single IP address, but the reverse isn’t true; an IP address
can map to only one FQDN. This means that forward and reverse entries frequently don’t match.
The reverse DNS entries are usually the responsibility of the ISP hosting your site, so it is quite
common for the reverse lookup to resolve to the ISP’s domain. This isn’t an important factor for

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