How to Fix Slow DNS Lookup: The Complete Troubleshooting Guide

Nowadays, in a high-tech world where people always stay online, even a slight delay of few seconds can irritate people and mess up their work. However, a slow website performance is not always caused by poor internet speed. But slow website performance is not only related to poor internet speed. It begins before any webpage loads; however, it is a DNS lookup that converts the domain name into an IP address on which the device is supposed to connect. Then, websites, applications and cloud services are all delayed before the content is even loading. 

Understanding how to fix slow DNS lookup issues usually involves targeted steps such as changing DNS servers, clearing outdated cache records, or identifying bottlenecks within the DNS resolution process. 

What Is DNS Lookup?

Resolving a domain name (e.g. google.com) to a numerical IP address (for instance, 192.168.2.1) convertible for a PC is the process of a DNS (Domain Name System) lookup. Think of DNS as a directory of telephone numbers of the Internet. Since users do not need to remember Copious numeric IP addresses anymore, they can just enter the website's name they want to open. 

How a DNS Lookup Typically Works

Here's a simple explanation of how the DNS lookup process typically goes unnoticed by us.

• Typing a domain into a browser: When a user types an address like example.com, their computer or mobile phone needs first to find the IP address that corresponds to this domain name.
• Check the local DNS cache: Both Browsers and Operating Systems by default will search for a previously stored DNS record. If the required IP address is already stored in the cache, then the device will proceed to connect without resorting to any further DNS queries.
• Querying a Recursive Resolver: If cached record are missing, the query is forwarded to a Recursive Resolver (usually provisioned by the user's ISP, or it may be a public DNS resolver like Cloudflare DNS, Google DNS).
• The resolver consults the Root Nameserver: The Root Nameserver will redirect the resolver to the appropriate Top-Level Domain (TLD) nameserver related to the domain extension, such as.com or.org.
• The TLD Nameserver responds: The TLD nameserver is the type of the nameserver that can inform you who is authoritative for the domain that you requested.
• The Authoritative Nameserver provides the IP address: The Authoritative Nameserver is the one which contains the true DNS records and it responds with the correct IP address for the domain.
• Browser loads the website: Once the IP address has been retrieved, the browser proceeds to establish a connection with the website server and initiates the website loading process.

Typically a DNS call lasts about 20 and 120 milliseconds. If you see that the lookup time is regularly above 150 milliseconds, then you may have a DNS performance issue that may even cause your website or app to become unavailable.

What Causes Slow DNS Lookup?

To determine why a DNS lookup is slow, first you need to know what factors cause the delay. We have reviewed the scenarios that mostly impinge on DNS lookup time. Here they are:

• Fed-up ISP DNS servers: ISP resolvers are used by thousands of users. They can respond to queries within 80-200 ms under the load.
• Sizeable distance: When the server is very far from the user, the network latency increases causing the DNS query to be slow.
• Stale/corrupted DNS cache: If a browser or OS stores an old or damaged DNS cache, it may cause a slow DNS lookup as opposed to a quick cached answer.
• Very small DNS TTL (Time to Live): When a website has a very small TTL, it results in frequent requirement of the device to visit the DNS to fetch new records rather than relying on the cache for a longer duration.
• IPv6 fallback delays: Networks try the IPv6 first for DNS routing. If the IPv6 connection is problematic or not supported, the system reverts to IPv4 after a set interval.
• Firewall or anti-virus resulting in interference: Security software, like Norton or Kaspersky, could be blocking and throttling DNS queries.
• VPN and virtual adapter causing interference: Legacy VPN clients may leave behind virtual adapters which can confuse the lookup priority of your system.
• Outdated network drivers or firmware: A driver that is not up-to-date may lead to disjointed query behavior.

Common Signs of DNS Performance Issues

There are several common signs of DNS performance issues that you should be aware of.

• While slow DNS doesn't always manifest itself clearly, there are several warning signs to look out for when there are DNS-related performance bottlenecks in websites, apps and the network.
• Delayed first page load: Pages can take a few seconds to load, typically because the DNS doesn't resolve the first time the website is requested.
• Normal internet speed, but slow browsing: It's possible to pass internet speed tests and yet websites may be slow, meaning that it's likely DNS lookups are the problem, not internet speed.
• DNS Errors like DNS_PROBE_FINISHED_NXDOMAIN, ERR_NAME_NOT_RESOLVED or “Server Not Found” typically mean that the DNS lookup has failed or that the DNS server being used is overloaded.
• Sometimes Websites are Accessible: Some websites may work while others do not, but the issue is random; this can be due to DNS cache issues or it can be because the route is slow or the resolver is not performing consistently.
• Tools such as Google PageSpeed Insights can give TTFB scores that are much higher than they should be, and may indicate that DNS is being resolved slowly prior to the start of content delivery.
• Different Behavior Across Networks: A site that performs well on mobile data, but not on WiFi, may be an indicator of DNS cache or resolver issues on a particular local network.
• Slow DNS can impact more than websites: Cloud services hosted on platforms like Amazon Web Services may also experience delays caused by slow DNS resolution, leading to email delivery issues, failed VoIP calls, and cloud application timeouts.
• DNS delays during deployments, during periods of high traffic or when many users are using a network concurrently.

How to Fix Slow DNS Lookup (Step-by-Step Solutions)

Slow DNS lookups are typically caused by devices using overloaded DNS servers, waiting an excessive amount of time for a non-responsive DNS server to respond, and/or using old cached information. The following methods can be used to increase the speed of DNS and decrease delay of the DNS lookups.

Method 1: Manually Change DNS Settings

This method works well for personal computers and does not require scripting or advanced technical knowledge.

Steps

1. Open the Settings by clicking on Wi-Fi or Ethernet in the taskbar.
2. Click on Network & Internet and then on Properties on the active network connection.
3. Navigate to the IP Assignment and edit.
4. Switch to Manual Mode.
5. Enable IPv4.
6. Enter the following DNS servers:
7. Preferred DNS: 1.1.1.1
8. Alternate DNS: 8.8.8.8
9. Save and reconnect to the network.

Why This Works

The DNS servers set on most devices are the default ones provided by the internet service provider. These servers may become overloaded during peak usage times which will lead to a higher DNS response time. Public DNS providers like Cloudflare and Google have extensive global DNS networks that have superior DNS infrastructure and performance, which helps to minimize the DNS lookup time.

Method 2: Use PowerShell for DNS Troubleshooting

PowerShell is the second method listed to troubleshoot DNS. In a business or managed IT environment, where you want to efficiently diagnose and correct issues with the management of DNS on multiple systems, PowerShell is apt to help.

Steps

1. Use Windows Search to find PowerShell and then run it as administrator.
2. To see what DNS servers are set as the current DNS server, use the following command: Get-DnsClientServerAddress. This command lists the active DNS servers which are currently bound to the device and can help detect stale or incorrect DNS entries such as old VPN-specific resolvers. 
3. Use Measure-Command to measure DNS lookup time: Measure-Command { Resolve-DnsName www.google.com }. If a website or internet speed problem is likely, it may be the result of DNS related delays, which could be caused by slow response times. 
4. To clear the local DNS cache, run: Clear-DnsClientCache. This will delete stale DNS entries from the system and cause new DNS lookups. It's safe and won't compromise personal files or passwords.

How Businesses Can Prevent DNS Slowdowns

Performance of DNS is a business and agency issue and not just one of technology. Just a couple of key practices make a difference.

• Use reasonable TTLs: With more longer TTLs, the resolvers will store the records for longer time, and that will decrease the number of repeated lookups. Any TTL between 86400 and 3600 seconds (24 hours to 1 hour) is considered reasonable and acceptable.
• Minimize CNAME records: CNAME records involve an extra DNS lookup. Review your DNS records and change any CNAMEs with ANAMEs where possible.
• You should resort to using a CDN-supported DNS provider: High-quality DNS providers such as Amazon Web Services’ AWS Route 53 significantly lower geographic distance delays through globally distributed DNS infrastructure.
• Track in real-time: DNSPerf, Catchpoint, or Sematext tool offers real-time and historical DNS performance information. Avoid surprises for your users by spotting slowdowns in advance.
• Set DNS configuration at router level: Making DNS setting at router level speeds up the setting process for every router-connected device, without having to configure each one individually.

For guest posting experts, site speed becomes a key factor influencing rankings and retention. While tools such as GuestPostCRM can help you stay on top of your link building workflow, it's just as crucial to ensure that your website performs well at the technical level as it is to create links.

Conclusion

One of the most frequent, yet ignored issues that affect browsing is slow DNS lookup. Luckily, many DNS performance problems can be resolved within a few minutes by changing the DNS server to a faster public DNS server, cleaning up cached DNS records and restarting the router. From managing one website to a portfolio of SEO clients via a tool like GuestPostCRM, DNS performance should be on anyone's technical SEO list, and the investment pays off every time.