What are Public DNS Servers?
DNS servers are responsible for resolving user-friendly domain names (like tech-faq.com) into computer-friendly IP addresses (such as 66.37.153.109).
Public DNS servers are DNS servers that respond to just about anyone.
Usually DNS servers will only respond to clients of a particular Internet Service Provider (ISP) network. Most DNS servers are private, and serve only those that own and maintain them. Some private DNS servers may appear to be public, but only because they haven’t been configured properly by the responsible system administrators. Usually, such problems are fixed and the DNS server becomes private.
Misuse
Incorrectly configured DNS servers may be susceptible to denial of service attacks. Such attacks are performed by sending so many queries to the server that it gets above the limit that the server can handle.
Other dangers faced by public DNS servers include pharming, cache poisoning and DNS amplification attacks.
List of Public DNS Servers
Here is a list of some of the available public DNS servers and their location.
* 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)
Cost for End Users
Public DNS servers’ services are provided free of charge by volunteer engineers. These services are usually run on UPS protected FreeBSD servers. The Internet Protocol (IP) addresses of these severs can be accessed through querying either the DNS or WHOIS database using any of these tools, dig, whois, dnsquery and nslookup. The free aspect of the DNS server services was, according to some industry players, a reaction to the high fees introduced by ISPs for otherwise simple and uncomplicated services.
Support for Zone Files
A public DNS server allows the user to write his own zone file and distribute it to the internet through public DNS hosts. Public DNS provides the name service while the domain owner can select a primary server that they directly control thus allowing the owner to administer/edit the zone data directly on a private machine.
Some public DNS servers might impose conditions for using them, especially in relation to zone file creation. Sending spam and other forms of unsolicited mail may result in the zone file of the culprit being excluded. Public name servers may also employ third party programs such as nslint to preempt common zone file errors.