Date: Sun, 02 Jul 2017 16:03:37 +0200 From: "Herbert J. Skuhra" <herbert@mailbox.org> To: freebsd-net@FreeBSD.org Subject: Re: [Bug 220351] Path MTU discovery works only after resetting an internal interface MTU (mpd5, ng_nat, ipfw) Message-ID: <87bmp3x7eu.wl-herbert@mailbox.org> In-Reply-To: <87r2xzaw30.wl-herbert@mailbox.org> References: <bug-220351-2472@https.bugs.freebsd.org/bugzilla/> <bug-220351-2472-lCDWr8PCgb@https.bugs.freebsd.org/bugzilla/> <87r2xzaw30.wl-herbert@mailbox.org>
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Herbert J Skuhra skrev: > > bugzilla-noreply skrev: >> >> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=220351 >> Eugene Grosbein <eugen@freebsd.org> changed: >> >> What |Removed |Added >> ---------------------------------------------------------------------------- >> Assignee|freebsd-net@FreeBSD.org |eugen@freebsd.org >> Status|New |Open >> CC| |eugen@freebsd.org >> >> --- Comment #2 from Eugene Grosbein <eugen@freebsd.org> --- >> (In reply to Martin Birgmeier from comment #1) >> >> Lowering interface MTU of internal machine also lowers its default route 'mtu' >> attribute, see output of the command 'route -n get default'. >> >> Raising interface MTU back does NOT restore 'mtu' attribute of the default >> route, so the kernel still uses 1492 as maximum IP packet size for packets >> going via this route. >> >> Correct solution for your problem is 'set iface enable tcpmssfix' command in >> the mpd.conf, see /usr/local/etc/mpd5/mpd.conf.sample for example. This way you >> can keep default MTU=1500 for internal hosts and have no MTU-related network >> problems. >> >> Please test and report back. > > I think I have a similar problem, but with IPv6 and pf! :-( > > - Problem to load e.g. https://www.heise.de on the first try > - Can not connect to Skype for Business over IPv6 (unfortunately I > sometimes need it for job) Skype for Business (S4B) on Mac OS X 10.12.6 (Beta5) is actually trying to connect over IPv4. The connection fails until I lower MTU to 1440. After resetting MTU to 1500 and restarting S4B it connects fine for a while ('route -n get' default shows 1500). I use 'set iface enable tcpmssfix' in mpd5.conf and I've tried: - set iface mtu and set link mtu/mru/mrru in mpd5.conf - set scrub ... max-mss in pf.conf -- Herbert
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