When you access a website or use an online service, your device needs to translate domain names (like rental-server.net) into IP addresses that computers use to locate each other. This is where Domain Name System (DNS) servers come into play. You can configure your devices with preferred and alternate DNS server addresses, but how exactly do these work together?
Typically, your operating system is configured with a list of DNS server addresses, often referred to as preferred, alternate, and sometimes even tertiary DNS servers. The common understanding might be that these servers are used in a load-balancing or immediate failover setup. However, the reality is slightly different.
By default, most operating systems, including Linux and Windows, primarily utilize the preferred DNS server for name resolution. Only when the preferred DNS server fails to respond, times out, or is unreachable will the system move on to query the alternate DNS server. This sequential approach means that the alternate DNS server is essentially a backup. If the primary DNS server responds – even with an answer indicating that a domain name does not exist – the system generally will not proceed to query the alternate server. It considers any valid response from the primary server as conclusive for that query.
To optimize your DNS resolution, especially in scenarios where you want to prioritize local network resolution while still leveraging public DNS servers like Google DNS or OpenDNS, you can employ strategic configurations. One effective method is to configure your router or gateway to use a public DNS server (e.g., 8.8.8.8) as its primary DNS. Ideally, this gateway device should also run its own DNS server, capable of resolving queries for local hostnames within your private network. If a query for a local hostname fails, the gateway should then forward the request to the public DNS server. This setup provides a balanced approach, ensuring fast resolution for local resources and reliable resolution for internet resources via public DNS.
Another advanced configuration involves assigning different DNS servers to different network interfaces. Operating systems like Windows inherently support this. Furthermore, for those using BIND9 DNS server software, directives like forward and forwarders can be configured to achieve similar outcomes, allowing for granular control over DNS server usage based on network context.
In summary, preferred and alternate DNS servers are not typically used simultaneously for every query. Instead, alternate servers serve as backups, activated only when the preferred server is unresponsive. Understanding this behavior is crucial for effective network configuration and troubleshooting DNS resolution issues.
