All versions prior to 5.6.x enable SIP ALG by default. You have to put the “config.ugw.voip.sip_alg_disable=true” in config.properties. https://help.ubnt.com/hc/en-us/articles/205146040-UniFi-config-properties-File-Explanation Double-check it’s in the right place and being applied. SSH to USG and run “show configuration commands |match modules”. Will see something like the following if it is: $ show configuration commands |match modules set system conntrack modules sip disable As long as you see the “sip disable” there, it’s disabled.
Disable SIP ALG on USG