On Fri, Oct 30, 2020 at 7:03 PM Strahil Nikolov <hunter86...@yahoo.com> wrote:
> in 4.3.10's UI it shows 1500 :) > > This might be just a misleading representation of the default value or an unknown value. If "Automatic Synchronization" is enabled for the ovirt-provider-ovn in oVirt Engine, the value should be updated in Engine to the correct after the next synchronization in the background. > > > > > > В петък, 30 октомври 2020 г., 13:25:05 Гринуич+2, Dominik Holler < > dhol...@redhat.com> написа: > > > > > > > > On Thu, Oct 29, 2020 at 9:36 PM Alex K <rightkickt...@gmail.com> wrote: > > > > > > On Tue, Oct 27, 2020, 02:49 Strahil Nikolov via Users <users@ovirt.org> > wrote: > >> Hello All, > >> > >> I would like to learn more about OVN and especially the maximum MTU > that I can use in my environment. > >> > >> Current Setup 4.3.10 > >> Network was created via UI -> MTU Custom -> 8976 -> Create on External > Provider -> Connect to Physical Network > >> > >> So my physical connection is MTU 9000 and I have read that Geneve uses > 24 bits (maybe that's wrong ?) , thus I have reduced the MTU to 8976. > > From the internet draft it seems that the tunnel header + reserved bits > comprise 64 bits. A common practice for Geneve implementations is to use > 8900 mtu for VMs when having 9000 mtu physical network. > > > > Ack, this is a safe choice. > In oVirt's default configuration, an overhead of 58 bytes > ( = 20 IPv4 header + 8 UDP header + 16 GENEVE Ethernet header (including 8 > bytes options) + 14 bytes inner Ethernet header) > is added. > This is why the default MTU for OVN networks in oVirt is 1442 bytes, which > assumes 1500 bytes MTU in the physical network. > > > > > > > The draft: > > https://tools.ietf.org/html/draft-ietf-nvo3-geneve-08 > >> > >> I did some testing on the VMs and ping with payload of '8914' was the > maximum I could pass without fragmenting and thus the MTU on the VMs was > set to 8942. > >> > >> Did I correctly configure the test network's MTU and am I understanding > it correctly that we need extra 34 bits inside the network for > encapsulation ? > >> > > You could check with packet analyzers like tcpdump and wireshark. > > >> I have checked > https://www.ovirt.org/develop/release-management/features/network/managed_mtu_for_vm_networks.html > but I don't see any refference how to calculate the max MTU. > >> > >> > >> Best Regards, > >> Strahil Nikolov > >> _______________________________________________ > >> Users mailing list -- users@ovirt.org > >> To unsubscribe send an email to users-le...@ovirt.org > >> Privacy Statement: https://www.ovirt.org/privacy-policy.html > >> oVirt Code of Conduct: > https://www.ovirt.org/community/about/community-guidelines/ > >> List Archives: > https://lists.ovirt.org/archives/list/users@ovirt.org/message/CKNS5T5KE2W5EIXBTGQDU3URKHQDVAM4/ > >> > >> > > _______________________________________________ > > Users mailing list -- users@ovirt.org > > To unsubscribe send an email to users-le...@ovirt.org > > Privacy Statement: https://www.ovirt.org/privacy-policy.html > > oVirt Code of Conduct: > https://www.ovirt.org/community/about/community-guidelines/ > > List Archives: > > > https://lists.ovirt.org/archives/list/users@ovirt.org/message/VIDP3MLYHWG2WXQ6JB6EHK66J5WBOMVT/ > > > > > _______________________________________________ > Users mailing list -- users@ovirt.org > To unsubscribe send an email to users-le...@ovirt.org > Privacy Statement: https://www.ovirt.org/privacy-policy.html > oVirt Code of Conduct: > https://www.ovirt.org/community/about/community-guidelines/ > List Archives: > > https://lists.ovirt.org/archives/list/users@ovirt.org/message/7UN5DXXKXN3KBLTLGXIPTGWVF4ODKKUB/ > >
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