Technical Tip: Audio through multicast protocol is not working in the FortiGate

While making a call from the client to the server, the user could not hear audio. There is already a configured VLAN to VLAN multicast policy, but for some reason, it is not working.

As per this scenario, there is alreadya  configured multi-cast policy. Make these changes in the firewall and check.

To prevent the TTL for forwarded packets from being changed:

config system setting
    set multicast-ttl-notchange enable
end

To enable multicast forwarding in NAT mode:

config system setting
    set multicast-forward enable
end

For testing purposes, disable the offloading policy traffic for hardware acceleration if the issue is still present.

config firewall multicast-policy

    edit <policy id>

        set auto-asic-offload disable

    end

Related document: 

Configuring multicast forwarding