[ntp:questions] Re: IPTable Rule to allow NTP thru ?

Jeff Boyce jboyce at meridianenv.com
Mon Aug 21 16:54:45 UTC 2006


>>Jeff Boyce wrote:
>>My general network setup is a dsl line coming into an ActionTec dsl modem
>>gateway doing NAT.
>
>Hal Murray replied:
>In addition to IPTables on your server, you may have to configure
>your NAT box to forward outside packets to UDP port 123 at your
>external IP address to your NTP server.  It probably depends
>on the fine print of your NAT box.  If a packet arrives for port 123,
>does it assume a low port number is for a server and check the server
>forwarding table, or does it look in the reply mapping table?
>
>You can test the IPTables rules by poking your server
>from inside your firewall with ntpq.

Yes, using ntpq, along with some other clues was what led me to the 
conclusion that it was the iptables firewall on the linux box that was 
blocking communication.  I believe the dsl modem gateway doing NAT would 
allow everything through properly, but will keep this in mind when I have 
the right firewall rule.  So I am down to just trying to figure out the 
proper firewall rule that I should use on the linux box now.

Jeff Boyce
www.meridianenv.com




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