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On Fri, Mar 30, 2007 at 08:27:50PM +0200, Manuel Bouyer wrote:
> On Fri, Mar 30, 2007 at 10:30:12AM -0500, Jonathan A. Kollasch wrote:
> > Hi
> >=20
> > I was helping a friend of mine debug weird issue with
> > Xen networking the other day.  The setup involves a
> > dom0 with a single NIC (fxp(4)), vlan(4) interfaces
> > attached to the fxp in the dom0, and bridged to additional
> > xennet(4) interfaces in the domU.  Because the xvif/xennet pair
> > seems to have a hard 1500 byte limit, the tagged packets can't
> > bridged without a drop in MTU, which is undesirable.
> >=20
> > Anyway, while from the dom0 the vlan(4) interfaces work
> > as expected, the connection of the domU's xennet to the
> > tagged frames on the copper is acting extremely weird.
> >=20
> > The domU can ping6 ff02::1%xennetX both itself and the xvif
> > in the dom0. The MAC table in the dom0's bridge for this interface
> > shows the addresses I expect it should, sometimes entries even
> > appear in the NDP/ARP tables in remote machines.  But not so
> > much as a icmp ping response seems to get received by the domU.
> >=20
> > So, outgoing from the domU seems to be working, but incoming
> > seems not to.
> >=20
> > All interfaces are marked up, and whatnot.
> >=20
> > I tested this on two 4.99.4 Xen3 dom0s,
> > and a 3.x Xen2 dom0 as well.  All the same.
> >=20
> > Any ideas of where to look for clues as to what's causing this?
>=20
> Yes: 802.1Q packets are forwarded to the vlan(4) layer and so the bridge
> never see them. This just won't work, the solution is to use one
> vif per vlan.

Hi, friend of jakllsch here.  My weird networking issue.

I currently have one vif per vlan.  The issue i was having is
slightly different than jakllsch's, in that I was trying to
communicate using domUs on two different dom0s.  on both the
dom0s, i have an fxp card, with a vlan interface - vlan216.  on
each dom0, i add vlan216 to bridge0, then associate the domU's
xennet device with bridge0.  And now, a poor attempt at ascii
art:

                         +-------+
                         | dom0a |
                         +-------+
                            fxp0
+-------+                     |
| domUa |xennet0--bridge0--vlan216-----\
+-------+                            +----------+
                                     |  switch  |
+-------+                            +----------+
| domUb |xennet0--bridge0--vlan216------/
+-------+                    |
                           fxp0
                         +-------+
                         | dom0b |
                         +-------+


i don't know, does this make sense? have i just embarassed myself
by showing the universe that i am not only no artist, but i don't
know how bridges and vlans work?  alas.  this is why i asked
jonathan to send the initial mail, i'll just make a hash of it.

if i put an IP on dom0a's vlan216 interface, it can ping domUb
without trouble.  when trying to ping domUb from domUa, the ping
is observed at domUa's xennet0 device, and the reply is observed
as far up the chain as the vlan216 interface of dom0a, but is not
seen anywhere on domUb or dom0b.
  --david

> --=20
> Manuel Bouyer <bouyer@antioche.eu.org>
>      NetBSD: 26 ans d'experience feront toujours la difference
> --

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