> On 11 Jul 2016, at 15:52, Sam Yaple <sam...@yaple.net> wrote: > > After lots of fun on IRC I have given up this battle. I am giving up quickly > because frickler has purposed a workaround (or better solution depending on > who you ask). So for all of you keeping track at home, if you want your vxlan > and your vlan networks to have the same MTU, here are the relevant options to > set as of Mitaka. > > [DEFAULT] > global_physnet_mtu = 1550 > [ml2] > path_mtu = 1550 > physical_network_mtus = physnet1:1500
I believe your request is corner case, and as long as we have a way to solve the issue for you, we should be ok. Note that if you use IPv6 endpoints, you need to use a higher value for path_mtu: https://review.openstack.org/#/c/320121/ > > This should go without saying, but i'll say it anyway: Your underlying > network interface must be at least 1550 MTU for the above config to result in > all instances receiving 1500 mtu regardless of network type. If you want some > extra IRC reading, there was a more extensive conversation about this [1]. > Good luck, you'll need it. > > [1] > http://eavesdrop.openstack.org/irclogs/%23openstack-neutron/%23openstack-neutron.2016-07-11.log.html#t2016-07-11T13:39:45 > > Sam Yaple > > On Mon, Jul 11, 2016 at 7:22 PM, Fox, Kevin M <kevin....@pnnl.gov> wrote: > I fought for two weeks to figure out why one of my clouds didn't seem to want > to work properly. It was in fact one of those helpful souls you mention below > filtering out PMTU's. I had to play with some rather gnarly iptables rules to > workaround the issue. -j TCPMSS --clamp-mss-to-pmtu.... > > So it does happen. > > Thanks, > Kevin > > From: Ian Wells [ijw.ubu...@cack.org.uk] > Sent: Monday, July 11, 2016 12:04 PM > To: OpenStack Development Mailing List (not for usage questions) > Subject: Re: [openstack-dev] Neutron and MTU advertisements -- post newton > > On 11 July 2016 at 11:49, Sean M. Collins <s...@coreitpro.com> wrote: > Sam Yaple wrote: > > In this situation, since you are mapping real-ips and the real world runs > > on 1500 mtu > > Don't be so certain about that assumption. The Internet is a very big > and diverse place.... > > OK, I'll contradict myself now - the original question wasn't L2 transit. > Never mind. > > That 'inter' bit is actually rather important. MTU applies to a layer 2 > domain, and routing is designed such that the MTUs on the two ports of a > router are irrelevant to each other. What the world does has no bearing on > the MTU I want on my L2 domain, and so Sam's point - 'I must choose the MTU > other people use' - is simply invalid. You might reasonably want your > Neutron router to have an external MTU of 1500, though, to do what he asks in > the face of some thoughtful soul filtering out PMTU exceeded messages. I > still think it comes back to the same thing as I suggested in my other mail. > > __________________________________________________________________________ > OpenStack Development Mailing List (not for usage questions) > Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > > __________________________________________________________________________ > OpenStack Development Mailing List (not for usage questions) > Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
