My FritzBox (with VOIP) is in front of an OpenWRT 18.06 box and if I connect a VOIP Phone over the Openwrt Box it blocks the the VOIP Channel back to the Phone (I can start a call but doesn't get back anything).
In the System Log I get this: "nf_conntrack default automatic helper assignment has been turned off for security reasons and CT based firewall rule..."
So I found two things:
I installed this package mentioned in this thread but it doesn't help.
So maybe I have to do something on the firewall side:
Can somebody transfer this actions to the OpenWrt Firewall Config?