I access SQL, RDP and many other items through my ipsec tunnel and I
never change the MTU on the client.   Thats a bad idea.    The
solution is to find out why the packets are getting frag'd.   Active
directory traffic does not work across my IPSEC tunnell but RDP and
friends surely do.   I would say there is something else causing the
fragmentation.   Another router before the pfSense machines?

Scott


On 10/10/05, Jason Landry <[EMAIL PROTECTED]> wrote:
> Well, here's an interesting side effect.
>
> I can no longer access the m0n0wall through the LAN address through the 
> tunnel.
>
> At home, I'm at 10.53.64.110
> The m0n0wall at work is at 192.168.1.1
>
> Before changing the MTU to 1400 on my client machine, I could simply
> go to 192.168.1.1 in my browser, and the tunnel would connect
> automatically, but Remote Desktop and SQL didn't work.
>
> Now that I've changed the MTU, I can't get to 192.168.1.1, but Remote
> Desktop and SQL both work.
>
> Is this just the nature of the beast?
>
> On 10/10/05, Jason Landry <[EMAIL PROTECTED]> wrote:
> > No, I'm just doing site-to-site with IPSec between a m0n0wall and
> > pfsense.   I made no configuration changes at all on client machines
> > until the 1400 MTU suggestion.  That did the trick.
> >
> >
> > On 10/10/05, Scott Ullrich <[EMAIL PROTECTED]> wrote:
> > > Running PPPoE as the client on Wan?
> > >
> > >
> > > On 10/10/05, Jason Landry <[EMAIL PROTECTED]> wrote:
> > > >
> > > > I tried setting the MTU on the WAN interface in pfsense to 1400 but
> > > > that didn't work.
> > > >
> > > > I set the MTU on my desktop machine to 1400...and everything works now
> > > > - sql & remote desktop.
> > > >
> > > > Thanks for the help!
> > > >
> > > > Jason
> > > >
> > > > On 10/10/05, Chris Buechler <[EMAIL PROTECTED]> wrote:
> > > > > Fleming, John (ZeroChaos) wrote:
> > > > >
> > > > > >I'm guessing we might need to do some mss fixup for ipsec tunnels.
> > > > > >
> > > > > >
> > > > >
> > > > > and you'd be right.  I'm not sure where it breaks down, but PMTUD is
> > > > > b0rk over IPsec tunnels.  Has always been an issue in m0n0wall.  I've
> > > > > looked at it some, but wasn't able to determine anything affirmatively
> > > > > other than "it's broken".  The MSS clamping in IPF in m0n0wall doesn't
> > > > > differentiate betweeen internet traffic and VPN traffic, and hence
> > > > > doesn't take into account the overhead of IPsec and doesn't solve the
> > > > > problem.
> > > > >
> > > > > The typical "solution" is to drop the MTU on LAN hosts until it works,
> > > > > people usually set it at 1400 (as a number that works, should be able 
> > > > > to
> > > > > squeeze more than that).  Depending on the characteristics of your
> > > > > network traffic, this can have a measurable negative impact on network
> > > > > performance, especially on the LAN with large data transfers.
> > > > >
> > > > >
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