[rhn-users] Re: NTP

[Nick Baronian]

Oops, the -p tcp was a typo on my part.
What I am really getting at is if there is a way to have ntp work like
some other client apps.  I want to sync to redhat's time server but I
don't want to have a constant connection.  Kinda like if I was ssh'ing
or ftp'ing into a server.  The server would be running the ssh/ftp
service and have port 22 or 21 open but my machine would open a random
non-priv port get my payload and then close it.
Is NTP different because the polling is so frequent?

Thanks,
Nick

On 11/2/06, Cameron Simpson <cs at zip.com.au> wrote:
> 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/
>
> Dope will carry you through times of no money better than money will carry
> you through times of no dope!   - Freewheelin' Franklin
>
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