Date: Fri, 30 Mar 2007 09:07:15 -0400 From: Sten Daniel Soersdal <netslists@gmail.com> To: eternityos@free.fr Cc: "freebsd-isp@freebsd.org" <freebsd-isp@freebsd.org> Subject: Re: MTU settings. Message-ID: <460D0B83.2010902@gmail.com> In-Reply-To: <1175128095.460b081f94385@imp.free.fr> References: <1175128095.460b081f94385@imp.free.fr>
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eternityos@free.fr wrote: > > Hi everyone :) > > Recently, we changed our internet connection to a ppp based (2Mbps). > So naturaly, I thought about changing the MTU of my interfaces on the FreeBSD > NAT router. > So I set it to 576 instead of the default, 1500 on the two interfaces, LAN and > WAN. > In what I have seen, 576 is the natural mtu for a ppp connection. 1500 is the natural mtu for ppp (lesser mtu sizes are the exception). You also contract a wide range of hard to diagnose problems, if you are not familiar with diagnosing mtu problems. > > Right away after this change, the internet connection blocked. I only got it > back setting the mtu back at 1500. > > Why did this block ? > Between the modem and the NAT router, we have a cisco router, I didn't change > it's mtu yet, would it be the cause ? It has to be negotiated during connection. ppp is a protocol which preferres the same settings on both ends of the ppp connection. Or atleast compatible ones. -- Sten Daniel Soersdal
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