Time to Live
TTL (Time to Live) is a setting for each DNS record that specifies how long a resolver is supposed to cache the DNS query before the query expires and a new query needs to be performed.
Use the command below to find out the TTL of a specific DNS record.
nslookup -debug blog.ictnsure.nl
This yields the following result from which can be seen that the TTL of DNS entry blog.ictnsure.nl is 1 hour.
Use the command below to find out the value of a specific DNS TXT-record.
nslookup -q=TXT _acme-challenge.blog.ictnsure.nl
This yields the following result from which the value of the TXT-record can be obtained.