I’ve been fighting with this issue for over a year. I even replaced a 210 with bigger model thinking that I might have too much activity for the 210 to handle (wasn’t the problem). Numerous visits from the internet provider (Time Warner) always said no trouble found.
The problem could be documented. If I run a ping from the Peplink router to the internet gateway (which is the cable modem directly attached) the ping times are inconsistent. Out of about 100 pings, 90 of them will be in the 2 or 3 ms range (remember we’re only going to the next device on a 3ft cord), but the other ten are all over the place. 20ms, 50ms, 70ms, some much longer. Those inconsistent times result in stutter or audio drop out on VoIP.
Yestereday I was reading the Peplink documentation on the Cable/DSL optimization feature. I always had it checked-on, thinking it must be a good thing. As I understand the description now, the feature will temporarily delay uplink in order to allow downstream to perform better. If my understanding is correct, might this have been my problem? I turned off the feature and like magic the VoIP problem went away. Hooray! I ran that ping test literally 200 times and every one is perfect.
Please elaborate if my understanding of how Cable/DSL optimization works is correct I suggest your next user guide point out that this feature may not be compatible with VoIP.