From owner-freebsd-questions@FreeBSD.ORG Tue Feb 9 12:12:24 2010 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 4866410656A5 for ; Tue, 9 Feb 2010 12:12:24 +0000 (UTC) (envelope-from h.schmalzbauer@omnilan.de) Received: from host.omnilan.net (host.omnilan.net [62.245.232.135]) by mx1.freebsd.org (Postfix) with ESMTP id C83918FC33 for ; Tue, 9 Feb 2010 12:12:23 +0000 (UTC) Received: from titan.flintsbach.schmalzbauer.de (titan.flintsbach.schmalzbauer.de [172.21.1.150]) (authenticated bits=0) by host.omnilan.net (8.13.8/8.13.8) with ESMTP id o19CCLTK043814 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Tue, 9 Feb 2010 13:12:22 +0100 (CET) (envelope-from h.schmalzbauer@omnilan.de) Message-ID: <4B715125.8070809@omnilan.de> Date: Tue, 09 Feb 2010 13:12:21 +0100 From: Harald Schmalzbauer Organization: OmniLAN User-Agent: Thunderbird 2.0.0.23 (X11/20090906) MIME-Version: 1.0 To: freebsd-questions@freebsd.org X-Enigmail-Version: 0.95.6 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigB4BB7E910E5D4D5BD007D7D5" Subject: MTU, fragmentation and Jumbo Frames question X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 09 Feb 2010 12:12:24 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigB4BB7E910E5D4D5BD007D7D5 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: quoted-printable Hello all, I have 3 machines connected to an JumboFrame enabled switch. One FreeBSD 8-stable and two windows machines. I can send echo requests with payload of 8972 between the windows=20 machines, but I don't get an answer from the FreeBSD machine. At the=20 edge of 8130 bytes, the FreeBSD machine eats the packets without any=20 error notification. A payload <=3D 8130 bytes works! All MTUs are set to 9000, interfaces are all intel em. Like mentioned, the ping between the two windows machines work like=20 expected, beyond 8972 bytes payload the OS is fragmenting (resp. tells=20 me that DF bit was set but fragmentation was needed) FreeBSD seems to never fragment packets, since I don't get an answer if=20 I define payload greater than MTU. But this should work, shouldn't it=20 (`ping -s 10000 host`) Does anybody have any explanation why pings are working up to 8130 bytes = payload and are silently droped beyond that even my MTU ist set to 9000=20 (and route get confirms the MTU 9000)? Thanks for any help, -Harry --------------enigB4BB7E910E5D4D5BD007D7D5 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.13 (FreeBSD) iEYEARECAAYFAktxUSUACgkQLDqVQ9VXb8gvMgCcC52QIP/ENPX4phXazLXtQscO dWwAoIT72cbbxHFw61rvGnZmu3JhRlWt =KNRY -----END PGP SIGNATURE----- --------------enigB4BB7E910E5D4D5BD007D7D5--