Date: Tue, 09 Feb 2010 20:22:59 +0800 From: Ilya Zhuravlev <i.a.zhuravlev@cbtnet.ru> To: Harald Schmalzbauer <h.schmalzbauer@omnilan.de> Cc: freebsd-questions@freebsd.org Subject: Re: MTU, fragmentation and Jumbo Frames question Message-ID: <4B7153A3.3000002@cbtnet.ru> In-Reply-To: <4B715125.8070809@omnilan.de> References: <4B715125.8070809@omnilan.de>
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On 09.02.2010 20:12, Harald Schmalzbauer wrote: > 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 > machines, but I don't get an answer from the FreeBSD machine. At the > edge of 8130 bytes, the FreeBSD machine eats the packets without any > error notification. A payload <= 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 > expected, beyond 8972 bytes payload the OS is fragmenting (resp. tells > me that DF bit was set but fragmentation was needed) > FreeBSD seems to never fragment packets, since I don't get an answer if > I define payload greater than MTU. But this should work, shouldn't it > (`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 > (and route get confirms the MTU 9000)? kern/143285 but "ifconfig em0 -rxcsum" is enough for me.
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