Good day everyone!
Within the local network, behind NAT (RB450) is VoIP server Asterisk, which is stored on the server provider. Calls proceed normally, his voice too, but as regards the case of the fax transmission protocol T38, mikrotik begins to create problems: packages t38 simply does not pass from the provider to the server via NAT. This is well illustrated in the diagram:


left - the dump is cleared by sniffer
right - on the server Asterisk.
What can I do?
SIP helper tried to turn on and off - does not help.
All rules on the router to make the default configuration of the web interface.

Hi,

Try after bypassing TCP & UDP 6004 port.

Try Upgrading to version 5.
It fixed my problems with FoIP

yes, it has decided my problem, but added one more: the utility sniffer is not working
thanks!

Hello,

I have the same problem with fax transmission through my new RB450 with RouterOS 4.17. I am not happy with using the v5 Beta firmware. Is the port-bypassing 6004 a solution? has anybody tried this? I can not test it by myself because the router is at the moment very far away.

thanks

Markus

thanks very much for this post. It's very useful to me. I have been battling with FoIP for weeks, I'll try and upgrade to 5.1 and see if that fixes the FoIP problem. I can't believe I dismissed the router as the possible cause. So many things with T.38 can go wrong, but I didn't think the router would be one of the causes.

Hello,

ok but this is not a real solution, because I can only find the version 5.0rc11. The last stable version is 4.17 and with this version there is no t.38 possible, or is there any other way to get it work with the version 4.17 ? When will version 5.1 be released ?

Regards Markus

It's more than one month hat I had this problem, today I made an upgrade, V5.0 installed. It works!