I am experiencing some odd behavior when using DNAT to redirect an Internet incoming port for RDP to my internal clients for RDP.
I can use any other port (including 1 port above or below the target port) without problem. I also get the same issue connecting to multiple difference clients (with different OSs) and from multiple different locations & clients. Nothing else is listening on this port on the client from what I can see with netstat.
There is no mention of the port being blocked etc in any logs that I can see (including Firewall and IPS logs) and I have made an exception in IPS for the target client but this has made no difference.
The errors I am getting when attempting to connect are:


I can telnet to the port, but I get the text below, rather than the standard response of nothing:
RFB 003.008
Anyone got any ideas how I can track the source of this down?
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