Based on your question, I'll consider that you're pretty much using a standard
iptables config.
edit /etc/sysconfig/iptables
Add the following line, somewhere in the middle - it allows inbound
connections to TCP port 22:
-A RH-Firewall-1-INPUT -p tcp --dport 22 -j ACCEPT
If you want to restrict access to a single IP address try this, - it allows
inbound connections to port 22 from ip address 1.2.3.4:
-A RH-Firewall-1-INPUT -p tcp -s 1.2.3.4/32 --dport 22 -j ACCEPT
Then restart iptables
/etc/rc.d/init.d/iptables restart;
Cheers!
-Ben
Or you could run /usr/bin/system-config-securitylevel for a GUI.
But -- if it turns out that you do not have firewall enabled, have you considered the possibility that you really don't have a route to the host? That's a network configuration issue on your client, not the ssh server.