I2P support forum

Running i2pd on Windows 10 Notebook.

Settings in i2pd.conf:
[upnp]
## Enable or disable UPnP: automatic port forwarding (enabled by default in WINDOWS, ANDROID)
enabled = true
## Name i2pd appears in UPnP forwardings list (default: I2Pd)
name = I2Pd

This results in i2pd.log:
20:46:10@897/error - UPnP: Found Internet Gateway Device http://192.168.178.1:49000/igdupnp/control/WANIPConn1
20:46:10@897/error - UPnP: Port forwarding to 192.168.178.20:9525 failed: return code 606
20:46:10@897/error - UPnP: Port forwarding to 192.168.178.20:18815 failed: return code 606
20:46:10@897/error - UPnP: Port forwarding to 192.168.178.20:9525 failed: return code 606
20:46:10@897/error - UPnP: Port forwarding to 192.168.178.20:9525 failed: return code 606

Network status is firewalled for v4 and v6.
But client tunnels and transit tunnels can be ceated. With moderate bandwidth. Router caps: X.

How can this be fixed?

Your router (Gateway) may need to explicitly allow UPnP port forwarding?