From: Chris Penney <cpenney@gmail.com>
Subject: Re: NAT & lockd
Date: Fri, 8 Apr 2005 10:08:00 -0400
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	 <1112967554.15565.58.camel@lade.trondhjem.org>
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> > nsm_mon_unmon: rpc failed, status=-13
> > lockd: cannot monitor x.x.x.x
> >
> > With our old NFS server I never got any messages.  The IP address
> > x.x.x.x is that of the NAT box.  I'm curious if this means locking
> > does not work behind nat or if it means something else.  Is there
> > anything I can do here?  Would a 2.6.x based NAT box have a more up to
> > date iptables that supports lockd?  This is non-critical, I'm just
> > trying to understand.
> 
> Locking under NFSv2/v3 is not very NAT or firewall-friendly and was one
> of the motivations for developing NFSv4.
> 
> The problem is that under NFSv2/v3, the protocol requires bi-directional
> communication (by which I mean that the server needs to be able to
> connect to the client, which is a problem for NAT as you can see above)
> and requires a bunch of helper-protocols that use different ports (which
> is a problem for firewalls).

In this situation (behind NAT), what happens with the client?  Will a
lock request fail or simply appear to always work?

Do I need to be concerned about the server reliability at all (ie. are
the messages harmless other than obviously the files not really being
locked)?

Thanks for the fast reply,

   Chris


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