Resolving name servers are very useful for dialup, cable modem, ADSL, DSL, VPN and similar users. A resolving name servers is provided by your ISP (internet service provider) or your organizations network admin or third party resolving name servers. Resolving name servers directly finds out information about the root servers, top level domains and authoritative name servers. It also speed up queries by caching results locallly as configured by hostmater in their domains’ TTL field.
- Name servers in delegations appear listed by name, rather than by IP address.
- A resolving name server must issue another DNS request to find out the IP address of the server to which it has been referred.
- Since this can introduce a circular dependency if the nameserver referred to is under the domain that it is authoritative of, it is occasionally necessary for the nameserver providing the delegation to also provide the IP address of the next nameserver. This record is called a glue record.
More About Resolver
You need to specify at least two resolving name server Internet address (in dot notation) that the resolver should query. A resolver is nothing but standard set of routines in the Operating Systems (or C library) which provide access to the Internet Domain Name System. You can set to 3 name servers. If there are multiple servers, the resolver library queries them in the order isted. If no nameserver entries are present, the default is to use the name server on the local machine. The algorithm used is to try a name server, and if the query times out, try the next, until out of name servers, then repeat trying all the name servers until a maximum number of retries are made).
Standard UNIX Resolver Configuration
The file /etc/resolv.conf file contains information that is read by the resolver routines the first time they are invoked by a process. The file is designed to be human readable and contains a list of keywords with values that provide various types of resolver information. Sample /etc/resolv.conf file:
nameserver 220.127.116.11 nameserver 18.104.22.168 nameserver 22.214.171.124
126.96.36.199, 188.8.131.52 and 184.108.40.206 are ISP resolving name server address. Type the following command at the terminal to view the current file contains:
Standard Mac OS X Resolver Configuration
The file /etc/resolv.conf file contains information about ISP resolving name server address. This file can be updated using GUI tools or network configuration options.
- Click on the System Preferences.
- Select Network.
- Select Built In Ethernet and click Advanced.
- Now you can view the current resolving name server.
You can also type the following command at the terminal to view the current file contains:
Standard Windows XP / Vista / Windows 7 Resolver Configuration
- Click the Stat button.
- Select Control Panel.
- Select View network status.
- Select Properties button.
- Select TCP/IPv6 > Properties.
- You can now see the resolving name server in the “Preferred DNS server”
You can also use the following procedure to view resolving name server IP address.
- Click on Start button
- Select Run
- Type command cmd
- Press [enter] key
- At DOS prompt type the command: