nanog mailing list archives
Re: IPv6 PMTUD and OS-X
From: Vyto Grigaliunas <vyto () fnal gov>
Date: Tue, 24 Aug 2010 13:15:46 -0500
1220? I am pretty sure the minimal IPv6 MTU is 1280 and that below it
fragmentation should be handled by the medium that transports packets smaller than that.... Can you enlighten me >> Bill? :) Please correct me if I'm wrong, but last I heard IPv6 routers do not do fragmentation...it's up to the IPv6 end hosts to properly determine the path MTU. Thanks... Vyto Date: Sat, 21 Aug 2010 11:42:04 +0200 From: Jeroen Massar <jeroen () unfix org> Subject: Re: IPv6 PMTUD and OS-X To: bmanning () vacation karoshi com Cc: nanog () nanog org Message-ID: <4C6F9F6C.80609 () unfix org> Content-Type: text/plain; charset=UTF-8 On 2010-08-21 09:18, bmanning () vacation karoshi com wrote:
On Fri, Aug 20, 2010 at 11:34:23PM +0200, Jeroen Massar wrote:On 2010-08-20 23:27, Franck Martin wrote:I'm trying to debug a pesky PMTUD issue with IPv6 on Mac OS-X 10.6. It happens only from home, on wireless, when connected to a mac aiport that does an automatic tunnel (teredo) to IPv6 backbone.Welcome to the great world of Teredo/6to4 where the endpoints/relays of the tunnel are anycasted in both IPv4 and IPv6 and thus can be quite difficult to debug, it can be done but requires quite a lot of vision in the network on both IPv4 and which will be generally near
impossible.
There are IPv6 web site that I cannot browse until I lower the MTU to1400. Why don't you just do 1280 which is the default? Do also note that you have two levels of PMTU, the IPv6 one and the IPv4 one. If you configure your MTU of the tunnel incorrectly compared to the relay that you are using you will not see the PMTU's coming through either or they might not accept your large packets. Both MTUs can be broken due to folks filtering ICMP which is generally a bad thing to do. Greets, Jeroenor - if you are tunneled more than once, you might be ultra
conservative
and drop your MTU to 1220 - that should weed out the edge cases
where even 1280
is too large.
1220? I am pretty sure the minimal IPv6 MTU is 1280 and that below it fragmentation should be handled by the medium that transports packets smaller than that.... Can you enlighten me Bill? :) Greets, Jeroen
Current thread:
- IPv6 PMTUD and OS-X Franck Martin (Aug 20)
- Re: IPv6 PMTUD and OS-X Jeroen Massar (Aug 20)
- Re: IPv6 PMTUD and OS-X Franck Martin (Aug 20)
- Re: IPv6 PMTUD and OS-X bmanning (Aug 21)
- Re: IPv6 PMTUD and OS-X Jeroen Massar (Aug 21)
- <Possible follow-ups>
- Re: IPv6 PMTUD and OS-X Vyto Grigaliunas (Aug 24)
- Re: IPv6 PMTUD and OS-X Jeroen Massar (Aug 20)