Use the dig command to test, as demonstrated in
Example 5.2, “Inspecting DNS entries with dig”
Example 5.2. Inspecting DNS entries with dig
$ dig -t naptr +short example.org 10 0 "s" "SIPS+D2T" "" _sips._tcp.example.org. $ dig -t srv +short _sips._tcp.example.org. 0 1 5061 sip-proxy.example.org.