Isn't OVS setting MTU automatically MTU for bridge as lowest value from ports connected to this bridge?
> Wiadomość napisana przez Miguel Angel Ajo Pelayo <majop...@redhat.com> w dniu > 22.09.2017, o godz. 10:32: > > I believe that one of the problems is that if you set a certain MTU in an OVS > switch, new connected ports will be automatically assigned to such MTU the > ovs-vswitchd daemon. > > > > On Wed, Sep 20, 2017 at 10:45 PM, Ian Wells <ijw.ubu...@cack.org.uk> wrote: > Since OVS is doing L2 forwarding, you should be fine setting the MTU to as > high as you choose, which would probably be the segment_mtu in the config, > since that's what it defines - the largest MTU that (from the Neutron API > perspective) is usable and (from the OVS perspective) will be used in the > system. A 1500MTU Neutron network will work fine over a 9000MTU OVS switch. > > What won't work is sending a 1500MTU network to a 9000MTU router port. So if > you're doing any L3 (where the packet arrives at an interface, rather than > travels a segment) you need to consider those MTUs in light of the Neutron > network they're attached to. > -- > Ian. > > On 20 September 2017 at 09:58, Ihar Hrachyshka <ihrac...@redhat.com> wrote: > On Wed, Sep 20, 2017 at 9:33 AM, Ajay Kalambur (akalambu) > <akala...@cisco.com> wrote: > > So I was forced to explicitly set the MTU on br-int > > ovs-vsctl set int br-int mtu_request=9000 > > > > > > Without this the tap device added to br-int would get MTU 1500 > > > > Would this be something the ovs l2 agent can handle since it creates the > > bridge? > > Yes, I guess we could do that if it fixes your problem. The issue > stems from the fact that we use a single bridge for different networks > with different MTUs, and it does break some assumptions kernel folks > make about a switch (that all attached ports steer traffic in the same > l2 domain, which is not the case because of flows we set). You may > want to report a bug against Neutron and we can then see how to handle > that. I will probably not be as simple as setting the value to 9000 > because different networks have different MTUs, and plugging those > mixed ports in the same bridge may trigger MTU updates on unrelated > tap devices. We will need to test how kernel behaves then. > > Also, you may be interested in reviewing an old openvswitch-dev@ > thread that I once started here: > https://mail.openvswitch.org/pipermail/ovs-dev/2016-June/316733.html > Sadly, I never followed up with a test scenario that wouldn't involve > OpenStack, for OVS folks to follow up on, so it never moved anywhere. > > Cheers, > Ihar > > __________________________________________________________________________ > 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 — Best regards Slawek Kaplonski sla...@kaplonski.pl __________________________________________________________________________ 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
