Zyxel H - Open VPN and slow UDP protocol

Kvemi

We would welcome a fix for UDP performance on FLEX H devices. TCP performs as expected, but UDP throughput is consistently very low. 😐️

Testing across multiple ISPs and configurations shows download speeds of approximately 4-8 MB/s and upload speeds of only 0.5-2 MB/s, despite both sites having 400 Mbps internet connections.In addition.

UDP support is important for many real-world deployments, as TCP can introduce overhead through retransmissions, acknowledgements, and congestion control, which may impact the performance of database replication, synchronization, and other latency-sensitive applications.

We believe this is a device or firmware limitation and would appreciate improvements in a future release.