[rhn-users] Re: NTP

[Cameron Simpson]

On 02Nov2006 15:20, Nick Baronian <kvetch at gmail.com> wrote:
| If I want to use NTP to sync to a time server does my machine have to
| open port 123 UDP.  I don't want to be a NTP server, I just want to be
| the client that polls a server.  I know I can use iptables to do
| something like
| $IPTABLES -A INPUT -j ACCEPT -p tcp -s 66.187.224.4 --dport 123
| But I would like to completely close the port if possible.
| Can this be done?

NTP uses udp, not tcp.
  $IPTABLES -A INPUT -j ACCEPT -p udp -s 66.187.224.4 --sport 123 --dport 123
and outbound (to make queries):
  $IPTABLES -A INPUT -j ACCEPT -p udp -d 66.187.224.4 --sport 123 --dport 123

Try that. It should be obvious you can't close the port completely - how
would ntp work it not traffic can flow?
-- 
Cameron Simpson <cs at zip.com.au> DoD#743
http://www.cskk.ezoshosting.com/cs/

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