On Wed, Apr 21, 2021, 23:56 Nikolaos Kakouros <n...@kth.se> wrote: > I am experimenting with openvpn and I try to understand how the mtu is > calculated. If I set `--link-mtu 1460`, then the tun0 mtu I see with `ip a` > is 1408. I understand that the IP + UDP headers are 28 bytes. What are the > other 24 bytes openvpn substracts? I thought it would have sth to do with > encryption, so I disabled encryption (using `--cipher none`), but the same > happened. >
link-mtu refers to maximum UDP payload size and doesn't include the IP (20 bytes) or UDP protocol header (8 bytes). It includes though the UDP encapsulation header of VPN. Thus, link mtu = tun mtu + vpn encapsulation > > _______________________________________________ > Openvpn-users mailing list > Openvpn-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/openvpn-users > >
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