Troubleshooting Network and DNS Connectivity

Being knowledgeable about how to check specific DNS records or network connectivity can be very helpful in troubleshooting problems with DNS and internet networks. Knowing what IP addresses are being used and which DNS records are showing can help a lot, especially when propagation for DNS records can take 24 hours and 48 hours for nameservers.

Common Troubleshooting Scenarios

• Email is not working — Are the correct MX records in place?
• Not sure where a website is hosted — Where are the A records pointing to?
• Not sure if A records are working — Does the IP address respond to a ping?
• Who owns a website or IP address — What does the WHOIS information show?
• Is my internet working — What results do you get from a traceroute?

Helpful Online Tools

• WHOIS Lookup — Look up domain registration info and DNS records
• WhatsMyDNS — Check DNS propagation worldwide
• MXToolbox — Comprehensive DNS and email diagnostics

Also, be mindful that your browser or local internet connection might cache old website files or DNS records. Clearing your cache or trying incognito/private mode can help.

Windows Network Command Line Tools

ping

• Tests reachability of an IP address or hostname
• Determines round-trip time
• Example: ping example.com
• Microsoft documentation

tracert

• Traces the path that a packet takes to its destination
• Maps the entire network path between you and the server
• Example: tracert example.com
• Microsoft documentation

whois

• Performs a registration record lookup for a domain name or IP address
• Example: whois example.com
• Microsoft documentation

nslookup

• Looks up information from DNS servers
• Finds canonical names, IP addresses, and more
• Example: nslookup example.com
• Example (specific record type): nslookup -type=mx example.com

Mac Terminal / Network Utility Tools

whois

• The internet domain name and network number directory service
• Example: whois example.com

ping

• Sends a request to network hosts to elicit a response
• Example: ping example.com

dig

• A flexible tool for interrogating DNS name servers
• Performs DNS lookups and displays the answers returned
• Example: dig example.com
• Example (specific record type): dig example.com MX
• Example (use specific DNS server): dig @8.8.8.8 example.com

traceroute

• Prints the route packets take to network hosts
• Example: traceroute example.com

Flushing DNS Cache

If you’ve made DNS changes but still see old results, try flushing your local DNS cache:

Windows

ipconfig /flushdns

Mac

sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

Linux

sudo systemd-resolve --flush-caches