From owner-freebsd-net@freebsd.org Mon Jul 13 16:56:32 2015 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 2047E99C963 for ; Mon, 13 Jul 2015 16:56:32 +0000 (UTC) (envelope-from jmg@gold.funkthat.com) Received: from gold.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "gold.funkthat.com", Issuer "gold.funkthat.com" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id EAE071CB8 for ; Mon, 13 Jul 2015 16:56:31 +0000 (UTC) (envelope-from jmg@gold.funkthat.com) Received: from gold.funkthat.com (localhost [127.0.0.1]) by gold.funkthat.com (8.14.5/8.14.5) with ESMTP id t6DGuVN0007062 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 13 Jul 2015 09:56:31 -0700 (PDT) (envelope-from jmg@gold.funkthat.com) Received: (from jmg@localhost) by gold.funkthat.com (8.14.5/8.14.5/Submit) id t6DGuVxJ007061; Mon, 13 Jul 2015 09:56:31 -0700 (PDT) (envelope-from jmg) Date: Mon, 13 Jul 2015 09:56:31 -0700 From: John-Mark Gurney To: Karl Pielorz Cc: freebsd-net@freebsd.org Subject: Re: lagg of em0/em1 + VLAN = lower MTU? Message-ID: <20150713165631.GN8523@funkthat.com> References: <7CFE75F7566F5789DAD9FBB2@[10.12.30.106]> <20150710180627.GA8523@funkthat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: FreeBSD 9.1-PRERELEASE amd64 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? User-Agent: Mutt/1.5.21 (2010-09-15) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (gold.funkthat.com [127.0.0.1]); Mon, 13 Jul 2015 09:56:31 -0700 (PDT) X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Jul 2015 16:56:32 -0000 Karl Pielorz wrote this message on Mon, Jul 13, 2015 at 09:33 +0100: > --On 10 July 2015 11:06 -0700 John-Mark Gurney wrote: > > > Try bumping the MTU on the root em's by 4 (1504) before creating the > > lagg... > > I had thought of that - but didn't want to try it (on the basis that out of > all the other example config's I've seen - no one else has to, and it will > break the lagg MTU). > > Anyway I tried it, by: > > - Bump the MTU on the em interfaces before creating the lagg to 1504 > > - The lagg created, inherits this 1504 MTU > > That breaks the untagged IP on lagg0 - i.e. I end up with: > > " > lagg0: flags=8843 metric 0 mtu 1504 > > options=4019b > ether 68:05:ca:08:1d:3b > inet x.x.x.x netmask 0xffffff00 broadcast y.y.y.y > " > > That MTU of 1504 is going to break lagg0 for untagged traffic :( > > > - However, the VLAN's setup on the lagg still default to 1496 MTU (despite > the underlying interface lagg0 being MTU 1504) > > If I 'manually' bump the MTU on the individual lagg0.x VLAN interfaces - > they will go to 1500, but traffic is still 'broken'. > > I can't 'reduce' the bad MTU on lagg0 either - i.e. 'ifconfig lagg0 mtu > 1500' (to try to put it back to 1500) fails with an ioctl error. > > So sadly, I'm still stuck :( You can fix the untagged traffic on lagg0 with something like the following: route change -mtu 1500 You can see which routes need to be changed w/ the netstat -rWnfinet command... > Something is lopping 4 bytes off the MTU when it shouldn't need to. None of > the example configs I could find were from 10.1-R (or with exactly the same > cards) - but obviously this is just bread & butter lagg/VLAN stuff, so it > should work? You should be able to make it work, but it definately needs more work to make it work automaticly... There was a recent change that went in that makes changing lagg mtu easier, but I think that's only in HEAD right now... Hope this helps... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."