Hi guys thanks for your post. but would some one please send me a detailed coding to accomplish this.this is what i want. to close all conections to the system except for some system whose addresses would be given.(pls use fetitious adresses i will understand),to change the default ssh port from 22 to 7777, to open port 80 for http, 100-200 for ntp and also 5555 udp to send data to wwlln.i have done extensive research on this and though it seem quite simple enough, i dont want to make any misstake on this.
Again assuming this box is behind a firewall how can the needed traffice be directed to it.
scripts can be sent to uwa_101@hotmail.com
Thanks.

To be honest, you've been shown everything you need to do in order to do this yourself. If you're concerned about mistakes, why don't you write your own rules and post them here (obviously with false IP addresses). I'm sure people will be glad to look over your work and point out any problems.

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Hi, okay i totally understand all about ssh now and i want to say this.
my setup is gonna be behind a firewall. clarkconnect to be precise and i know all i need to do to allow connection to the linux box running ssh is to do a port forwarding. now can the same be applicable to NTP. can i port forward from the firewall to the system running the NTP as well?

Yeah, the firewall doesn't know what is running on the ports it forwards, so it should work exactly the same way for all ports you want to forward.

Thanks alot Hangdog you all have really been of great help.

I'm glad I could help. And the offer still stands, if you need a review of iptables rules, post them here and I'm sure you'll get plenty of suggestions.