Re: [Openvpn-users] Link mtu warnings

[Alex K <rig...@gm...>]

Hi Jan,

Yes, I use ncp-disable on client side so as to be able to have per client
cipher negotiation.
How can one have ncp-disable and avoid link MTU issues?

Thanx,
Alex


On Mon, Sep 18, 2017 at 7:43 PM, Jan Just Keijser <ja...@ni...> wrote:

> Hi Alex,
>
> On 15/09/17 18:54, Alex K wrote:
>
> Hi all,
>
> I am receiving the below warning on server and client side when setting up
> the tunnel:
>
> server:
> Fri Sep 15 16:45:14 2017 172.30.0.180:44304 WARNING: 'link-mtu' is used
> inconsistently, local='link-mtu 1562', remote='link-mtu 1530'
>
> client:
> Fri Sep 15 16:45:14 2017 us=87436 WARNING: 'link-mtu' is used
> inconsistently, local='link-mtu 1530', remote='link-mtu 1562'
>
> and further down on client side:
> Fri Sep 15 16:45:15 2017 us=282768 OPTIONS IMPORT: adjusting link_mtu to
> 1629
>
>
> I have on server side:
> tun-mtu 1500
> fragment 1360
> mssfix
>
>
> and on client side exactly the same:
> tun-mtu 1500
> fragment 1360
> mssfix
>
> The tun interfaces on both sides show as 1500 with ifconfig.
>
> Why is this case? I cannot recall seeing such warning on openvpn 2.2.1-8.
> I can provide more details if needed.
>
>
> the link-mtu size also depends on the cipher and auth used ; are you using
> NCP at all (i.e. do you explicitly specify 'disable-ncp' ?)   A log file of
> a failing client with 'verb 4' set would help.
>
> HTH,
>
> JJK
>
>