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Managing DNS Servers
- Article
- 06/11/2021
- 2 minutes to read
In this article
A DNS Server is a computer that completes the process of name resolution in DNS. DNS Servers contain files, called zone files, that enable them to resolve names to IP addresses (or vice versa). When queried, a DNS Server responds in one of three ways:
- The server returns the requested name-resolution or IP-resolution information.
- The server returns a pointer to another DNS Server that can service the request.
- The server indicates that it does not have the requested information.
DNS Servers might, during the course of preparing to return the requested resolution information, query other DNS Servers. But beyond that, DNS Servers do not perform any operations other than those mentioned in the previous list.
There are three main kinds of DNS Servers — primary servers, secondary servers, and caching servers. See DNS Servers for more information on these DNS Servers.
Administration Steps
The DNS WMI Provider enables the administration of DNS Servers from the server itself, or from remote hosts. The general steps necessary to administer a DNS Server using the DNS WMI Provider are:
- Connecting to the DNS WMI Provider
- Getting a server instance
- Listing or modifying a server property, or using a method
To illustrate how to implement those administration steps, examples are provided. The following tasks are linked to their associated scripting samples.
- Stopping a DNS Server
- Starting a DNS Server
- Restarting a DNS Server
- Adding an IP Address
- Removing an IP Address
- Listing DNS Server Properties
- Displaying DNS Server Property Types
- Modifying DNS Server Properties
Prerequisite – Domain Name Server
Mapping a domain name to an IP Address is known as Name-Address Resolution. The Domain Name Server (DNS) Resolver performs this operation by consulting name servers.
In order to find a particular DNS requesting host place its query to the Local DNS Server with a mapping request. If it has the information, the resolver is satisfied else the resolver is referred to other servers or other servers are asked to provide the information. After the resolver, gets the response, it checks whether the response is correct or not. If the response is correct, the response is passed to the process that requested it, else the name query fails.
A resolution can be of two types – iterative and recursive.
1. Recursive Resolution –
Here, the client requires the Local Server to give
either the requested mapping or an error message. A DNS Query is generated by the application program to the resolver to fetch the destination IP Address. The Query is then forward to the local DNS Server. If it knows the IP Address, it sends a response to the resolver. Assuming, it does not know the IP Address, it sends the query to the root name server.
The root name server contains information about at least one server of Top Level Domain. The query is then sent to the respective Top-Level Domain server. If it contains the mapping, the response is sent back to the root server and then to the host’s local server. If it doesn’t contain the mapping, it should contain the IP Address of the destination’s local DNS Server. The local DNS server knows the destination host’s IP Address. The information is then sent back to the top-level domain server, then to the root server and then to the host’s Local DNS Server, and finally to the host.
2. Iterative Resolution –
The main difference between iterative and recursive resolution is that here each server that does not know the mapping sends the IP Address of the next server to the one requested it. Here, the client allows the server to return the best answer it can give as a match or as a referral. A DNS Query is generated by the application program to the resolver to fetch the
destination IP Address. The Query is then forward to the local DNS Server. Assuming, it does not know the IP Address, it sends the query to the root name server.
The root name server returns the IP Address of the Top-Level Domain Server to the Local Server. The Top-Level Domain server is contacted by the Local Server and it returns either the IP of the destination host or its local DNS Server. If it returns the server’s address, then by contacting the destination’s Local DNS Server, we get the IP Address of the destination host. The response/mapping is then passed from the host’s local DNS server to the resolver and then finally to the host.
Caching Mechanism –
In both iterative and recursive resolution, after a server asks for a mapping request from another server, it receives the response and stores this information in the Cache memory before sending it to the client. This is done to lower the search time it takes for a server to
check the IP Address in its Database. So, the next time, if a request comes to the server, it first checks its cache memory and tries to resolve the request. The response is marked as Unauthoritative to inform the client that the response is from Cache. The only way caching can be problematic is when the server caches the mapping for a long time and the mapping gets outdated. However, there are techniques to resolve this like using TTL.