How to Route MT SMS to an SMPP Client in Jasmin SMPP Server

Question

I need following routing:

3. GSM Gateway (SMPP Client, behind NAT: 192.168.1.101)
        ^
        |
2. Jasmin SMPP Server (Public IP: ip.x.y.z)
        ^
        |
1. SMS Generator (third party, public IP SMPP Client: ip.a.b.c)

My Jasmin server has two SMPP users: 1. gateway1:passwd, 2: client1:passwd

client1 is used by the originating third party SMPP client.

gateway1 is used by the terminating GSM gateway.

I cannot add an SMPP Client Connector to my Jasmin Server to connect to the Gateway because it is behind NAT.

How can I re-route an SMS coming from an SMPP client to another SMPP client in Jasmin SMS Gateway ?