Querying DNS Servers upon NXDOMAIN Response: Preferred One?
In Windows 10, when a DNS query is made, and a non-existent domain (NXDOMAIN) response is received, querying the DNS servers for additional information is a common practice. However, the question arises: which DNS server should be preferred for these queries? This article will explore the context of DNS queries, NXDOMAIN responses, and the preferred DNS server for Windows 10.
DNS Queries and NXDOMAIN Responses
When a user types a URL into their browser, a DNS query is made to translate the URL into an IP address. This query is sent to a DNS server, which checks its cache for the IP address. If the DNS server does not have the IP address, it will query other DNS servers until it finds the correct IP address or receives an NXDOMAIN response.
An NXDOMAIN response indicates that the domain does not exist. In other words, the DNS server is informing the client that the requested domain name does not have an IP address associated with it. When an NXDOMAIN response is received, Windows 10 may query other DNS servers for additional information.
Preferred DNS Server for NXDOMAIN Queries
In Windows 10, the preferred DNS server for NXDOMAIN queries is the one that was used for the initial query. This is because the initial DNS server is the most likely to have the most up-to-date information. However, if the initial DNS server does not respond or is unavailable, Windows 10 will query other DNS servers in the order specified in the network settings.
Case Example: DNS1.com Queries example1.com and DNS2.com Queries example2.com
In this example, DNS1.com is queried for example1.com, and DNS2.com is queried for example2.com. If an NXDOMAIN response is received for example1.com, Windows 10 will query other DNS servers using the order specified in the network settings. However, if an NXDOMAIN response is received for example2.com, Windows 10 will query other DNS servers using DNS2.com as the preferred DNS server.
In conclusion, when a DNS query results in an NXDOMAIN response, Windows 10 will query other DNS servers for additional information. The preferred DNS server for these queries is the one that was used for the initial query. By understanding the context of DNS queries and NXDOMAIN responses, network administrators can optimize their network settings for optimal performance.
References
- Microsoft. (2021). DNS Client Service.
- Microsoft. (2021). DNS Server.
- TechTarget. (2021). NXDOMAIN.
// Example code for querying a DNS server
using System;
using System.Net;
using System.Net.Sockets;
class Program {
static void Main() {
// Create a UdpClient for sending the query
UdpClient client = new UdpClient();
// Define the DNS query
string query = "example1.com";
byte[] queryBytes = System.Text.Encoding.ASCII.GetBytes(query);
// Define the DNS server to query
IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("8.8.8.8"), 53);
// Send the query to the DNS server
client.Send(queryBytes, queryBytes.Length, serverEndPoint);
// Receive the response from the DNS server
byte[] responseBytes = client.Receive(ref serverEndPoint);
// Print the response
Console.WriteLine(System.Text.Encoding.ASCII.GetString(responseBytes));
// Close the UdpClient
client.Close();
}
}