Date: Mon, 10 Sep 2007 20:01:40 +0100 From: Tom Judge <tom@tomjudge.com> To: Ivan Alexandrovich <ivsan@ngs.ru> Cc: freebsd-net@freebsd.org Subject: Re: nested vlans and ethernet frame size Message-ID: <46E59494.7040507@tomjudge.com> In-Reply-To: <web-95343829@mx1.intranet.ru>
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Ivan Alexandrovich wrote: > Hi > > I'd like to ask for advice - what is the right place for > setting maximum ethernet frame size in freebsd? > It needs 1526 bytes to allow two vlan tags per packet. > Those tags must be processed by ng_vlan code so > it seems that vlanmtu interface flag will be of no use here. > We're running freebsd6.2-stable and use some Intel pro 100 > card for testing purposes along with QinQ-capable switch. > > Currently frames of 1526 length are sent without problems but > incoming packets of such a size are lost. Since fxp driver > complains about 'discarding oversize frame' it can be supposed that > the problem in this case is not in nic hardware but in > driver. > > As far as I can see in kernel sources (it's a pity I'm not a > programmer :) many ethernet drivers use ETHERNET_MAX_FRAME macro > to define size checks. > Possibly I could replace "1518" by "1526" in sys/net/ethernet.h > but it must be considered brutal, isn't it ? :) > > > Thanks in advance, > Ivan This fix does not support N depth nesting, also if you are exceeding 1518 does that not imply at you require hardware that supports jumbo frames to do VLAN tag nesting? Tomhome | help
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