[ntp:questions] Re: ntpd without binding?

t_pascal at my-deja.com t_pascal at my-deja.com
Sun Aug 14 19:02:47 UTC 2005

Danny Mayer wrote:
> t_pascal at my-deja.com wrote:
> > Using ntp-4.1.2 on RedHat ES 3, I'd like to configure a "client only"
> > ntp system.  Easy enough to edit ntp.conf, but I'm trying to get ntpd
> > to stop listening on port 123 (blocked by iptables anyway).  Any way to
> > stop binding to interfaces, or select which (internal) interface I want
> > to listen only?
> >
> Well I implemented an option to specify which interface to listen on,
> but it will bind all other the others anyway but drop any packets it
> receives on those interfaces. It will always listen on the loopback
> addresses so you can do local queries. It's in the latest development
> builds. -L eth0 is the command line option but I believe that the letter
> will be changed.

I don't know if that is good, but I will wait to see.  The general idea
is that I don't want any ports bound on (for example) a bastion host,
even if I have a firewall, packet filter router, etc., in front of it.
I suppose it's OK to have a LAN full of clients who listen on ports
they'll never use (still a security problem, but whatever), but not on
security audited, outward facing machines.

The only other alternative is run ntpdate periodically, which is what
I've been doing since 1996 (at least).

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