[ovs-discuss] How does MTU work with tunnels?

Benjamin benjamin.reis at vates.fr
Tue Sep 10 13:48:36 UTC 2019

Thanks for your quick answer.

But i'm not sure I understand what you're saying: max MTU for VxLAN 
would be 1320?

Le 10/09/2019 à 15:26, Heim, Dennis a écrit :
> I run VXLAN over a DMVPN setup, as it is part of our Lab/PoC architecture (distributed). From an MTU perspective, Windows is happy with 1360, but some linux/apache servers require it set to 1320 to work properly.
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> -----Original Message-----
> From: ovs-discuss-bounces at openvswitch.org <ovs-discuss-bounces at openvswitch.org> On Behalf Of Benjamin
> Sent: Tuesday, September 10, 2019 9:04 AM
> To: ovs-discuss at openvswitch.org
> Subject: [ovs-discuss] How does MTU work with tunnels?
> Hi all,
> I working with openvswitch 2.5.3 (tried with 2.11.0 same behavior) on XCP-ng (XenServer fork).
> I'm trying to undersand how the mtu works with GRE and VxLAN tunnels.
> As for now when I create a GRE tunnel with any MTU, I think the MTU is not taken in consideration because i can ping -s 15000 on the corresponding interface.
> However, with VxLAN if I set a MTU greater than 1450 then the MTU is
> 1450 and if I set a MTU lower than 1450 I have same behavior as for GRE.
> So I'm a but confused.
> When I check the mtu value with : ovs-vsctl get int xapi0 mtu_request or ovs-vsctl get int xapi0 mtu the returned value is what I expect.
> Thanks in advance,
> Benjamin
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