On Tuesday 21 February 2006 19:04, Benjamin Rutt wrote:
> Jeff Dike <[EMAIL PROTECTED]> writes:
> > Run a UML on the one machine you have root on as the gateway to the
> > outside world - either with TUN/TAP or a uml_switch attached to a
> > TUN/TAP device.
> okay, I am trying to implement your suggestion (I am starting with
> getting this single UML up and running with access to the outside
> world, on the box I actually have root on) and I ran into a problem.
Ok, I've read and it's a well-known one.
Since you used a non-routable IP for the UML and the host, the echo-request
arrives to the foreign host, but it can't route it back, nor the default
gateway of that host can.
And the solution is not to add a route back (which obviously wouldn't scale,
and wouldn't work when pinging outside hosts), but to use Source NAT /
masquerading (-j SNAT / -j MASQUERADE). The same way you'd have to do if
sharing a dialup / home connection with only 1 public IP among various hosts,
so you can look at the tons of HOWTOs and explaination about the issue if you
need.
Indeed, with
arp -Ds 192.168.0.253 eth0 pub
you've setup proxy ARP.
If the LAN address had been 192.168.0.0/24 it would have been enough - the
foreign host would have had a route to the LAN for the UML address and sent
an ARP request. Again, for the whole LAN to connect to the outside someone
would have setup a NAT for it.
But it's not the case.
> PING 140.254.80.34 (140.254.80.34): 56 data bytes
> 64 bytes from 140.254.80.34: icmp_seq=0 ttl=64 time=1.5 ms
> 64 bytes from 140.254.80.34: icmp_seq=1 ttl=64 time=0.5 ms
>
> --- 140.254.80.34 ping statistics ---
> 2 packets transmitted, 2 packets received, 0% packet loss
> round-trip min/avg/max = 0.5/1.0/1.5 ms
> (none):~# ping 140.254.80.4
> PING 140.254.80.4 (140.254.80.4): 56 data bytes
> So it appears that the packets coming from the guest are not able to
> be forwarded across the host's network. Does anyone see what I might
> be doing wrong?
> Thank you,
--
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade
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