I'm root on a machine I don't know how it was configured.

I try to open SSHD on another port than 22 but it does not work.

I changed the /etc/ssh/sshd_config file and added a new Port line extra to the Port 22.

but it does only work when this second port is a number above 1024. Why is that? How can I find the reason?

Infos:

I'm restarting it using /etc/init.d/sshd restart as root.

"netstat -apn" does not show the port is open by any other service (anyway I tried different ports and only above 1024 work).

"telnet localhost port" also shows the service works only when they are above 1024.

In iptables all tables are empty.

Thanks!