From mboxrd@z Thu Jan 1 00:00:00 1970 From: Fabio Coatti Subject: Re: nfs, tap & vlan issues Date: Thu, 18 Sep 2008 20:53:00 +0200 Message-ID: <200809182053.00933.cova@ferrara.linux.it> References: <200809181847.39402.cova@ferrara.linux.it> <90eb1dc70809181011r6ae90877n5437b1889bed3009@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: kvm@vger.kernel.org To: "Javier Guerra" Return-path: Received: from cadalboia.ferrara.linux.it ([195.110.122.101]:53324 "EHLO cadalboia.ferrara.linux.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752983AbYIRSxF convert rfc822-to-8bit (ORCPT ); Thu, 18 Sep 2008 14:53:05 -0400 In-Reply-To: <90eb1dc70809181011r6ae90877n5437b1889bed3009@mail.gmail.com> Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: gioved=C3=AC 18 settembre 2008, Javier Guerra ha scritto: > On Thu, Sep 18, 2008 at 11:47 AM, Fabio Coatti =20 wrote: > > The network on guest machine is set up like this: > > 1: lo: mtu 16436 qdisc noqueue > > link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 > > inet 127.0.0.1/8 brd 127.255.255.255 scope host lo > > 2: eth0: mtu 1500 qdisc pfifo_fas= t qlen > > 1000 link/ether de:ad:be:ef:15:05 brd ff:ff:ff:ff:ff:ff > > 3: vlan3@eth0: mtu 1500 qdisc noq= ueue > > link/ether de:ad:be:ef:15:05 brd ff:ff:ff:ff:ff:ff > > inet 192.168.0.5/24 brd 192.168.61.255 scope global vlan3 > > 4: vlan4@eth0: mtu 1500 qdisc noq= ueue > > link/ether de:ad:be:ef:15:05 brd ff:ff:ff:ff:ff:ff > > inet 10.0.0.33/24 brd 10.0.0.255 scope global vlan4 > > there's your problem: > > your vlan interfaces (vlan3@eth0, vlan4@eth0) have an MTU of 1500. to > encapsulate that in eth0, it has to add 4 bytes of tagging, therefore > eth0 should have an MTU of 1504. also, the bridge and eth1 on Dom0 > must have MTUs of 1504. > > i don't know if the bridge can support 1504, if not, you would have t= o > set eth0 at 1500, and the vlan interfaces at 1496 I see your point; I've tried right now... and it worked! Thanks for you= r help,=20 really greatly appreciated. Anyway, a small detail: At first, I've tried to bring host interfaces (eth1,kvmbr0 and tap0) up= to=20 1504, no problem. Then I've started guest machine and tried to raise et= h0 to=20 1504, but it seems that virtio driver refuses mtu bigger than 1500. So the only difference with your recipe is that I've left all host inte= rfaces=20 (physical, tap and bridge) to an MTU of 1500 and set, on guest, eth0 to= 1500,=20 vlans to 1496. So it was eth0 on guest to complain and not bridge, but now it's workin= g like=20 a charm. (I was sure to have tried even the combination you suggested, in all my= tries,=20 but obvously I was wrong) --=20 =46abio "Cova" Coatti http://members.ferrara.linux.it/cova =20 =46errara Linux Users Group http://ferrara.linux.it GnuPG fp:9765 A5B6 6843 17BC A646 BE8C FA56 373A 5374 C703 Old SysOps never die... they simply forget their password.