I was having an issue where my T41P phones were getting provisioned with IPv4 & IPv6 - even though I specified in default settings yealink_ip_address_mode=0 for IPv4 only. Checked the y000000000036.cfg, which was setting it correctly. The issue was that {$mac}.cfg was overriding the correct setting. There were several instances of "network.ip_address_mode = 2" in this file, which specifies ipv4&ipv6. I changed all 5 of those entries in this file to pull from the default setting {$yealink_ip_address_mode} rather than just setting a static value of 2. I don't know why it has this listed in this file 5 times. But, this change resolved my issue and will force the T41P provisioning to follow FusionPBX default settings.