Message
Small packets pass, large ones do not
Small packets pass, large ones do not: what the ForestVPN message net.mtu_blackhole means, why it appears and what to do about it.
Updated October 11, 2026
The app says: "Small packets pass, large ones don't."
What it means
Small requests work and large transfers stall, so some pages half-load.
What to do
Try a different network. On computers the app may lower its packet size by itself where that is allowed; it never raises it.
Why it happens
Some network paths silently drop large packets. Switching to another location does not fix this.
Where you see it
The ForestVPN apps show this message on the connection screen, and in a notification when it affects your connection. The code is net.mtu_blackhole.