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List:       openvswitch-discuss
Subject:    [ovs-discuss] Openvswitch
From:       fbl () redhat ! com (Flavio Leitner)
Date:       2014-02-26 23:58:28
Message-ID: 20140226235828.GA25148 () t520 ! redhat ! com
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On Wed, Feb 26, 2014 at 11:42:09PM +0200, Antti Antinoja wrote:
> Hi,
> 
> We have been using the ovs source provided module since there where some \
> difficulties with gre tunnels + MTU.  
> ping with small package size passed through, but testing for example with -s 1500 \
> did not.  
> Maybe there is some way to make this to work with the Kernel provided module too?
> 
> With the ovs src provided module the GRE are working fine. Of course I'm not sure \
> if we do it efficiently (like not causing defragmentation continuously).

What version are you using? Because Path MTU is no longer supported.

The problem is that when the packet is encapsulated, its size increases
with the addition of the tunneling header. If the final size is above
the MTU, then the packet is dropped.  The Path MTU can discovery the
real MTU and adjust it.

So, you can work around the MTU issue by reducing it directly on the
interface which will have the same final result.

fbl


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