Xen users - Apr 2008 - Looking for easy guide for Fedora 8 xen networking

Hello,
  I''m hoping someone on this list can help me out.  I''ve been
using XEN
for a while now on FC6,7, RHEL 5, and gentoo.  I recently received a new
laptop that I''ve installed Fedora 8 on and plan to run XEN.

  From the other environments I''ve used, the networking "just
works" for
the guest if there''s only 1 nic card.  It stays on the same subnet as
the dom0 and everything works like the guest has its own network card.

  In using Fedora 8, the default networking appears to create a bridged
device and put it on a 192.168.122 subnet.  If the domU requests a DHCP
address, this nic provides it and the domU stays on the 192.168.122
subnet.  I can get out from the domU, but I can''t seem to get in.  My
first thought was just to change the subnet on this bridge, so I dug
around and found the file where it was located and put in my standard
subnet.  Same result, I can get out from the domU but can''t get in.
I''ve also noticed that if using virbr0 as the device that I pass to my
Vista domU, it recognizes a new network everytime I boot.  I have a
static MAC address in the config file, so I wouldn''t expect that... but
then again this is my first time playing with Vista too so I''m not sure
if it''s a product of virbr0 or just Vista being itself.

  I''ve searched the internet for a little bit hoping to find a simple
guide, but have only found a few posting here and there.  Most of which
seem to indicate ignoring the the network-bridge script all together and
creating my own bridge in sysconfig/network-scripts.  I''m not opposed
to
doing that, but I would prefer not to.

  Basically I''m hoping someone on this list has setup Fedora 8
networking already and can provide me a little advice or point me to a
guide that I''ve missed.  I just want the network to work like it did in
previous releases.


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Jason Solan wrote:
>   From the other environments I''ve used, the networking "just
works" for
> the guest if there''s only 1 nic card.  It stays on the same subnet
as
> the dom0 and everything works like the guest has its own network card.
>
>   In using Fedora 8, the default networking appears to create a bridged
> device and put it on a 192.168.122 subnet.  If the domU requests a DHCP
> address, this nic provides it and the domU stays on the 192.168.122
> subnet.  I can get out from the domU, but I can''t seem to get in.
There are two bridges, IIRC, virtbr0 for a local network (which is what 
you''re using) and eth0.  Previously the you would have had something 
like virbr0 and xenbr0 where xenbr0 has dom0''s eth0 and peth0 on it; in
Fedora8 eth0 is the bridge instead.  You probably want to use that 
instead of virbr0.

Now that the bridge has an IP address you can, again IIRC, do cool 
things with iptables for traffic flowing through the bridge without 
having to use ebtables.

jch

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On Fri, 2008-04-25 at 15:57 +0100, John Haxby wrote:
> There are two bridges, IIRC, virtbr0 for a local network (which is what 
> you''re using) and eth0.  Previously the you would have had
something
> like virbr0 and xenbr0 where xenbr0 has dom0''s eth0 and peth0 on
it; in
> Fedora8 eth0 is the bridge instead.  You probably want to use that 
> instead of virbr0.
Thanks for the reply. Unfortunately I still can''t seem to make it work.
I''ve switched my guests to use eth2 instead of virbr0, but now they
can''t seem to get any connectivity.  I assumed this is what you were
saying to do correct?.  With a guest booted, here is what brctl shows.

bridge name     bridge id               STP enabled     interfaces
eth2            8000.00022d8b1e44       no              peth2
                                                        tap0
                                                        vif2.0
virbr0          8000.000000000000       yes

That looks pretty much the same as the other systems I''ve used, but it
still doesn''t seem to work.
> Now that the bridge has an IP address you can, again IIRC, do cool 
> things with iptables for traffic flowing through the bridge without 
> having to use ebtables.
> 
Is it possible that I *have* to write iptables rules to get traffic to
flow through?

BTW, eth2 is my default network device, all others are disabled.

Any help is appreciated.


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On Wed, 2008-04-30 at 14:42 -0400, Jason Solan wrote:
> On Fri, 2008-04-25 at 15:57 +0100, John Haxby wrote:
> > There are two bridges, IIRC, virtbr0 for a local network (which is
what
> > you''re using) and eth0.  Previously the you would have had
something
> > like virbr0 and xenbr0 where xenbr0 has dom0''s eth0 and peth0
on it; in
> > Fedora8 eth0 is the bridge instead.  You probably want to use that 
> > instead of virbr0.
> 
> Thanks for the reply. Unfortunately I still can''t seem to make it
work.
> I''ve switched my guests to use eth2 instead of virbr0, but now
they
> can''t seem to get any connectivity.  I assumed this is what you
were
> saying to do correct?.  With a guest booted, here is what brctl shows.
> 
> bridge name     bridge id               STP enabled     interfaces
> eth2            8000.00022d8b1e44       no              peth2
>                                                         tap0
>                                                         vif2.0
> virbr0          8000.000000000000       yes
> 
> That looks pretty much the same as the other systems I''ve used,
but it
> still doesn''t seem to work.
Ok after a couple more tests it turns out this is because I''m using a
wireless nic.  If I use eth0 (hardwire) then the eth0 bridge works as I
would expect.
I don''t quite understand why this is, perhaps someone can explain it to
me?  If eth2 is bridged to a physical device, then as long as that
physical device is up and working, I don''t see why a guest should not
be
able to use it.  Am I missing something?
The wireless network is pretty much static for me.  I could understand
that switching to a new access point mid-stream may cause problems, but
I would think that just getting it up and running should work.

Anyone have any insight?



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Jason Solan wrote:
> Ok after a couple more tests it turns out this is because I''m
using a
> wireless nic.  If I use eth0 (hardwire) then the eth0 bridge works as I
> would expect.
Aha!  Wireless NICs can''t (yet) be put into promiscuous mode which is 
why it doesn''t work.

You get exactly the same trouble trying to use a wireless NIC as a 
bridge in VMware.

jch

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On Friday May 02 2008 07:02:21 am John Haxby wrote:
> Jason Solan wrote:
> > Ok after a couple more tests it turns out this is because I''m
using a
> > wireless nic.  If I use eth0 (hardwire) then the eth0 bridge works as
I
> > would expect.
>
> Aha!  Wireless NICs can''t (yet) be put into promiscuous mode which
is
> why it doesn''t work.
>
> You get exactly the same trouble trying to use a wireless NIC as a
> bridge in VMware.
Also, AFAIK, you can''t mix 802.1 & .11 ( or .16) on a bridge. You
can use a
wireless card in routing mode.

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