NAT issues using VoIP and Wireguard von OpenWRT

Ahoy friends.
Currently i'm running my setup, 2 routed networks, one having an OpenWRT device as VPN client and the other one having a VPN Peer.
My VoIP device is connected to the OpenWRT network and should perform calls by routing to the other network.
It works fine, but other people can't here me on the phone.
So i opened an issue on the cisco forums, but i still can't find out what the problem is.
According to the Cisco forums it might be a NAT bug in OpenWRT, so the RTP packets don't reach my target network at all.

How can i solve such complicated NAT related problems? According to my firewall there is only a NAT rule for WAN --> Reject.
Do i need a new firewall rule maybe to solve this problem?

Is there a good reason to enable NAT on a site to site tunnel?

As far as i know there is no NAT enabled it all.
The problem seems to be in the target network
The traffic should go to the router, but the VPN peer is, and somehow it's not reaching According to the Cisco forums because of a NAT bug somewhere.


So please explain how it could be a NAT bug, if you're not running NAT in tunnel?

What does this statement mean?

Can you show a config or picture?

The only thing that I'm aware of that indicates NAT on WAN is the Masquerade checkbox.

Then your problem is with asymmetric routing and gateway inspecting packets which finds correctly invalid, as the first packet of the session didn't go through it.

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Thanks for your help! You were right, there was an abandoned NAT rule in the target network, after removing it, it works.

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