Some network appliances impose a delay on returning a valid SSH banner when setting up a connection as a 'security' measure.
The only way around this is to either monitor on a simple tcp port 22 connection, or adjust the Timeout option in the zabbix_server.conf which is a bit overkill.

For these devices it would be really handy to be able to pass a timeout parameter to the itemkey:

net.tcp.service[ssh,<ip>,<port>,<timeout>]

Or something similar.

Preferably we could use a userparameter to supply the timeout value so we can adjust a generic template on the hostlevel if needed.