New Content #14508
openOptimizing MTU for VPN Tunnels
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Description
- OpenVPN
- IPsec (routed/policy)
- WireGuard
The following assumes a WAN link MTU of 1500
. Further testing, e.g. using ping, can be done to optimize the value. Examples of this testing should be provided. The optimized value is set on the interface assignment configuration.
OpenVPN
Setting the MTU on the assigned interface (Interfaces > Assignments) will not work correctly since the OpenVPN daemon sets the MTU to 1500 explicitly. Instead, the value should be configured as a custom option in the server/client configuration. The suggested value is tun-mtu 1428
to account for IPv6
+ UDP
+ OpenVPN Data
headers.
IPsec VTI
A starting MTU value of 1400
is used by default which accounts for most tunnel configurations.
WireGuard
Similarly to IPsec VTI, a the starting MTU value of 1420
is used by default.