Date: Sun, 29 Apr 2012 20:25:22 +0400 From: Lev Serebryakov <lev@FreeBSD.org> To: Seth Mos <seth.mos@dds.nl> Cc: freebsd-net@freebsd.org Subject: Re: IPv6 MTU discrovery -- how should it work? Message-ID: <882834004.20120429202522@serebryakov.spb.ru> In-Reply-To: <2vl4qolvow9yktrrufp56o2n.1335716454950@email.android.com> References: <2vl4qolvow9yktrrufp56o2n.1335716454950@email.android.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Hello, Seth.
You wrote 29 =D0=B0=D0=BF=D1=80=D0=B5=D0=BB=D1=8F 2012 =D0=B3., 20:20:54:
SM> Make sure you do not block icmp6. Or atleast make sure that
SM> unreachable and toobig packets come through even if you do not want ech=
o.
icmp6 enabled in firewall. It seems to be problem in "gif" interface,
which has this words in BUGS section in man page:
If the outer protocol is IPv4, gif does not try to perform path MTU di=
s-
covery for the encapsulated packet (DF bit is set to 0).
If the outer protocol is IPv6, path MTU discovery for encapsulated pac=
k-
ets may affect communication over the interface. The first bigger-tha=
n-
pmtu packet may be lost. To avoid the problem, you may want to set the
interface MTU for gif to 1240 or smaller, when the outer header is IPv6
and the inner header is IPv4.
I have MTU 1460 on my "outer" interface (it is PPPoE connection to my
IPv4 provider), and gif0 doesn't allow me to set mtu 1240 on it.
--=20
// Black Lion AKA Lev Serebryakov <lev@FreeBSD.org>
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?882834004.20120429202522>