Using your own VPN over a JPPS connection
Updated Oct 8, 2026
Most people never notice anything. If you connect to a work or personal VPN through a JPPS connection and it feels slow, stalls on big transfers, or drops during video calls, this page is for you.
What is going on
Our connection joins several internet links into one. That adds a small amount of wrapping to every packet, so the biggest packet it can carry in one piece is 1368 bytes. Normal websites and downloads adjust to this automatically.
A VPN adds its own wrapping on top. If the VPN's packets are larger than 1368 bytes, they get split into pieces. The connection still works, but it is slower, and one lost piece throws away the whole packet. That is most noticeable on a cellular link.
Which VPNs need a change
| Your VPN | What to do |
|---|---|
| OpenVPN over TCP, or an SSL VPN such as AnyConnect over TCP | Nothing. These work as they are. |
| WireGuard | Set the interface MTU to 1280. The default of 1420 is too big. |
| OpenVPN over UDP | Set tun-mtu 1280 and mssfix 1240. |
| IKEv2 or IPsec, including L2TP/IPsec | Set the tunnel MTU to 1280 if your client allows it. If it doesn't, ask your IT contact. |
1280 is a safe choice for every VPN type, and it is also the smallest size IPv6 allows. You give up a few percent of speed in exchange for stable connections.
WireGuard example
In your WireGuard configuration, under [Interface]:
MTU = 1280
OpenVPN example
In your OpenVPN configuration file:
tun-mtu 1280
mssfix 1240
Checking it yourself
From a computer on our connection, run this ping with the "don't fragment" flag set:
- Linux or macOS:
ping -M do -s 1340 example.com(on macOS useping -D -s 1340 example.com) - Windows:
ping -f -l 1340 example.com
A reply means a 1368-byte packet fits. Try one byte more (1341) and it should fail with a "too big" message. That shows where the limit is.
Still having trouble?
Tell us which VPN you use and what you see, such as slow transfers, stalls or disconnects. We will take a look. Open an issue on the mlvpn-rs project or contact us through jpps.us.