At least in version 2.7.2 and close, SIP-ALG is apparently (seen via live logs and behavior…) active within a Watchguard, if you have a TCP-UDP proxy active. Doesn’t matter how much you turn off in that proxy, SIP-ALG is still active. The only way to handle it, apparently, is by disabling the policy altogether and replacing it with a TCP-UDP packet filter.
Disable SIP-ALG on Watchguard firewalls
article #1495, updated 241 days ago
Mitel Connect download
article #1358, updated 1186 days ago
Here is a working URL:
SIP phone (VOIP) on Android
article #315, updated 4361 days ago
“CSipSimple” works quite well. It has auto-setup wizards for an excellent and very large variety of services, including both free and non-free varieties, internationally. Its market page is here:
As of this writing it works just fine with FastVOIP and IPKall.