What are Public DNS Servers?

When a person types in a web address or URL into the address box of a browser, the site name has to be resolved into an IP address before the remote computer can be accessed. This translation or resolving is done by DNS servers, of which Public DNS Servers are ones which respond to everyone.

Generally, DNS servers only respond to the clients of a particular Internet Service Provider or ISP network and most are private, serving only their owners and maintainers. There are also some ill-configured private DNS servers which can appear public unless the configuration problems are fixed.

Poorly configured DNS Servers can face denial of service attacks brought about by the sending of more queries than the amount the server can handle. Public DNS Servers may also face the problems of pharming, DNS amplification attacks and cache poisoning.

Some Public DNS Servers are:
* 208.185.249.250 (San Jose, CA, US)
* 216.87.84.214 (Longmont, CO, US)
* 208.185.249.251 (San Jose, CA, US)
* 131.161.247.231 (Oakland, CA, US)
* 66.227.42.140 (Dallas, TX, US)
* 65.243.92.254 (US)
* 217.115.138.24 (Cologne, Germany)
* 219.127.89.37 (Tokyo, Japan)
* 219.127.89.34 (Tokyo, Japan)
* 202.89.131.4 (Auckland, New Zealand)
* 64.151.103.120 (San Francisco, CA, US)
* 67.102.133.222 (Los Angeles, CA, US)
* 199.166.29.3 (Amsterdam, Nederland)

End users are provided the services of Public DNS Servers free of cost by volunteer engineers, with the services being run on FreeBSD servers that are UPS protected. The IP addresses of such servers can be addressed through the use of tools like dig, whois, dnsquery and nslookup to query the DNS or WHOIS database. In the opinion of some in the industry, DNS server services were provided free of charge in response to the high fees demanded by ISPs.

A public DNS server offers support for Zone Files, allowing a user to create his or her own zone file, which may then be distributed over the Internet through public DNS servers. The owner can privately edit zone data directly as the name service is provided by the public DNS while the domain owner selects a primary server which is controlled directly.

However, conditions may be imposed by some public DNS servers regarding the creation of zone files. This acts as a control in preventing spam and other unwelcome mail from being sent. Common zone file errors may also be forestalled by public name servers with the help of third-party programs like nslint.