Poor Call Quality on SIP Phones


I recently purchased a Pepwave Soho MK3 for the failover to cellular data capability. I have a number of SIP phones running on VirtualPBX. The call quality on my end is outstanding; however, my voice is usually broken up to the other party. I have played with many settings but cannot get improvement. My call quality both ways is close to perfect on my old Netgear router. I have QoS enabled for both SIP and RTP, and I have SIP Service Passthrough set to Compatibility. My cable Internet has issues with latency, and it seems that the Pepwave is much more sensitive to that than the Netgear. Any suggestions?


Hi, have you tried disabling SIP ALG in the support menu? Its enabled by default and has to be disabled via the radio button.

I’ve had a few instances where the SIP provider insists this is disabled before they will entertain troubleshooting at their end as it is often the cause of issued with SIP. Usually it blocks call setup rather than causes breakup (which would suggest packet loss) but its worth looking at to see if it resolves.


Yes, I have SIP ALG disabled. I should have mentioned that. Thanks for your reply. I keep experimenting and going back to my Netgear router where the calls sound so much better even though there is a little bit of breakup now since the latency is bad.


It sounds like your main issue is high latency and/or packet loss but the difference on the Netgear is interesting.

Have you looked into MTU values on the Netgear vs the Peplink?


Yes, I have previously done testing regarding the MTU and have both routers set at 1500.