NSLOOKUP & DNS servers - diagnose DNS issues

In order to determine the cause of DNS issues, try using the NSLOOKUP tool (Windows computers). Before you do, you almost certainly will want to perform a DNS query or PING from within you local router so as to determine the router's ability to connect to a DNS server.

DNS servers: although we and our partner networks assign DNS servers automatically, we will never be as fast or predictable as the internet giants such as Cisco, IBM and Google. For the very fastest DNS lookups, we recommend the servers at the end of this article.

Open a command prompt (Hold the Windows key and tap the X key, then choose Command Prompt)

Type the following, and press Enter:

nslookup cnn.com 8.8.8.8

This will attempt to resolve the domain cnn.com using Google's DNS servers (bypassing the local router or settings in the local computer)

You can also test using Cisco's DNS servers (instead of 8.8.8.8): 208.67.222.222 and 208.67.220.220

If you get no response, test if a firewall is blocking DNS queries by PINGing the DNS:

ping 8.8.8.8

If no reply, try to see at which node the traffic is failing:

tracert 8.8.8.8

Let us know the above test results if you wish to have us help diagnose further...

DNS servers

Our recommended DNS servers, which you can specify manually in your router or clients are:

• Cisco: 208.67.222.222 and 208.67.220.220
  • The Cisco DNS servers offer free anti-phishing and security protection
• IBM: 9.9.9.9
  • The IBM servers add an additional layer of free DNS security
• CloudFlare
  • 1.1.1.1 - low latency - very fast, and free to use
  • 1.1.1.2 - free anti-malware DNS
  • 1.1.1.3 - blocks most adult content
• Google: 8.8.8.8

DNS fine tuning for performance

To get the very best DNS response times, check https://www.dnsperf.com/ and use local tools such as trace route (tracert) to measure the fastest DNS servers near to your public IP.