Problem with voip fragmentation

[DavidePenno]

Hi, everyone.
I'm stuck with this problem form week anc i don't know how to solve it.
I think the problem is simble but i missing somethink.

Here the problem :
I have an internet connection with TIM ( italian operator ), i change the ISP modem with a frizbox 7490, after the modem is installed my pfsense and on my LAN there is a 3CX voip server.
The 3CX voip server can make any call i want, but i can't recive some call ( call caming from people that use the same ISP as mine ).
3CX pass all firewall test witouth any problem, and the call caming form other ISP work perfectly.

I run Packet Capture on WAN and on LAN side to see what happen and i discover that the call that i can recive are not fragmentated, insted the call tha i canot recive are fragmentated and the package of this call can't pass the firewall.
All the call use the same port 5060, and came from the same server, the only difference that i can see is the framentation of pacage...
Probably i missing something, but why pfsense can correctly rute the call not fragmented but drop the fragmented one ?

Anyone have been trought same problem or have any suggestion ?

Annexed the image of packet capure of WAN and LAN side.
WAN side :

LAN side:

[stephenw10]

So the reassembled packet is simply not transmitted to the PBX on the LAN? Are those over sized packets flagged do-not-fragment?

You can try setting either 'Disable Firewall Scrub' or if it is flagged 'IP Do-Not-Fragment compatibility' in System > Advanced > Firewall & NAT

Steve

[DavidePenno]

@stephenw10 Thank you so much, problem solved, i change the setting that you suggest to me and now work perfectly.