Re: [Openvpn-users] OpenVPN tunnel stopped working (no traffic) after upgrade to OpenVPN 2.7 (Fedora 44)

Hi,

On 18/05/2026 15:58, Piotr Dobrogost wrote:
> On Mon, May 18, 2026 at 9:22 AM Antonio Quartulli <[email protected]> wrote:
>>
>> Piotr, not sure I asked before: could you check the stats with 'ip -s
>> link ovpn-sfx' ?
> 
> I will, but in the meantime, I wanted to ask a question: is dco on the
> server and client totally independent in the sense that it can be
> turned on only on one side and not on the other side, and it would
> work on the side where it's turned on?
> Reading the answer to the question "Do both the client and server need
> to support DCO?" at
> https://blog.openvpn.net/openvpn-data-channel-offload-dco-the-definitive-guide-to-the-performance-boost-making-openvpn-the-fastest-vpn-protocol
> I would think so, but maybe I'm wrong, and the reason it does not work
> is simply that it's turned off on the server side?
> 

They are fully independent.

DCO just re-implements the data channel in kernel space, but it does not 
change the protocol.

Therefore DCO is fully transparent from a protocol perspective.

It can be enabled on either side and things will still work.

[[ Otherwise it would be fun connecting FreeBSD to a Linux server with 
DCO if this was not the case.. :) ]]

The only downside is that DCO does not support all features that 
userspace has, therefore if you try to use any of those, openvpn will 
simply disable DCO in order to connect.

But the connection is still expected to work.

Regards,


> 
> Regards,
> Piotr

-- 
Antonio Quartulli



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