How to troubleshoot DNS issues on macOS

Published: 28 January 2018
Filed Under: macOS

Below are a few methods and tools to help troubleshoot DNS on a Mac. This includes displaying the current DNS configuration, clearing your DNS cache, how to query a DNS server, and to even view the current DNS cache.

Display DNS configuration

To display your DNS configuration, run the following command from a terminal.

scutil --dns

Clear DNS cache

Sometimes you need to clear you DNS cache. In order to do this, run the following commands from a terminal. Depending on your browser, you may need to also close your browser and clear it's own cache.

sudo killall -HUP mDNSResponder
sudo dscacheutil -flushcache

Query DNS with nslookup

If you need to do simple lookups you can use nslookup to query a DNS server for a response.

# query default DNS server
nslookup applesoap.com

# query Google's Public DNS Server
nslookup 
server 8.8.8.8
applesoap.com

Query DNS with dig

If you need a more advanced view or need to trace the steps of DNS query, the dig tool is very useful.

# query all results
dig applesoap.com ANY

# query A records
dig applesoap.com A

# query MX records
dig applesoap.com MX

# query NS records
dig applesoap.com NS

# query using a specific nameserver
dig @ns-166.awsdns-20.com applesoap.com

# trace the path taken of a query
dig applesoap.com +trace

View DNS cache

Open Console, select your local machine, and search for mDNSResponder. Then open a terminal and type the command below. This will dump the current DNS cache into the console window.

sudo killall -INFO mDNSResponder