tnsping (and others) take at least 5 seconds (or longer)

I ran into a situation where tnsping and other connections like ssh and such took at least 5 seconds (5000 msec) to establish:

Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = host.domain.local)(PORT = 1521))
                                     (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = ORCL)))
OK (5010 msec)

Also connecting to ‘host.domain.local’ with ssh took about 5 seconds. At first I thought it had to with sshd and some authentication options which had to timeout first, but than I discovered tnsping also waits 5 seconds. When connecting to the ip address it took 0 msec… aha… a DNS thing?! Continue reading