I too am having this problem.
I followed the steam guide step by step. I am running a Virtual machine on a separate pc (AMD 8 Core FX) with Debian 8... Everything seems to be working as I can see clients join my server and leave... I am running RCON from the PC that I will be gaming on and had no problems connecting with "Wolfs Wargame RCON" to my virtual machine. I'v Double & triple checked login ID/Code givin from Eugen but all is in order.
I am using ports 10803 and 10805 from my router and have opened them in my Virtual Box in Adapter #1 under my NAT and Bridged Adapter #2. The only issue iv noticed is that in the steam guide, the instructions tell you to use the local IP from the Bridged Adapter; but when i run the /sbin/ifconfig command this is all i get from the Bridged Adapter--->
eth1 Link encap:Ethernet HWaddr XX:XX:XX:XX:XX:XX
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:6 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
RX bytes:360 (360.0 B) TX bytes:0 (0.0 B)
Eth1 does no provide me with an IP. So to connect Wolfs RCON to my VirtualBox from my gaming PC, I used the local IP assigned by my router and it connected w/o problem.
Any Help is VERY VERY VERY much appreciated as iv literally spent hours messing with settings trying to be able to view my server in game...
EDIT: I AM USING A HITRON CGN3 ROUTER
EDIT #2: my Friend was in fact able to view my server and load into it... so the issue is within my NAT i think but im at a loss on how to fix this. I do have access to my router for port forwarding and made sure everything is TCP/UDP and both pc's connected share the same external IP but I currently have the ports forwarded to the hosting PC and am unable to open the same ports for another PC on a different IP..... long story short im lost and confused