Date: Mon, 26 Mar 2012 07:16:50 -0700 From: Michael Sierchio <kudzu@tenebras.com> To: =?UTF-8?B?0JLQu9Cw0LTQuNGB0LvQsNCyINCf0YDQvtC00LDQvQ==?= <universite@ukr.net> Cc: net@freebsd.org Subject: Re: The problem with MTU <1500 Message-ID: <CAHu1Y70%2BSrqg4aE9tuVxq5E4nRSTFdi9_tVZ9J6O8anCUrJpYA@mail.gmail.com> In-Reply-To: <8904.1332769428.5720084203749900288@ffe15.ukr.net> References: <8904.1332769428.5720084203749900288@ffe15.ukr.net>
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2012/3/26 =D0=92=D0=BB=D0=B0=D0=B4=D0=B8=D1=81=D0=BB=D0=B0=D0=B2 =D0=9F=D1= =80=D0=BE=D0=B4=D0=B0=D0=BD <universite@ukr.net> > > Dear all! > I have two different values of uplink MTU - 1440 and 1492. > And in a local network - 1500. > In Cisco routers can be set 'set ip df 0', but I have no such router :( > What options are there for FreeBSD? > man ifconfig - not the 'mtu' option. You should set the MTU size on the interface to match the uplink MTU. And you should make sure you handle ICMP need-frag error messages, otherwise Path MTU discovery will be broken. Only use the net/tcpmssd? That's a workaround for not properly handling ICMP error messages, and just for TCP ;-) > Will it be possible to process both two channels of 1Gb? > > Never. ;-) Not in practice. What is the bandwidth - delay product? That's a fraction of the 1Gbps you'll never get. - M
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