Cyprus Broadband

About the ports on the Primetel's modem:

All the ports from 1025 until 60000 are open and forwarded on the internal ip 192.168.2.10. (If you want you can call them on 133 and ask them to open the rest ports from 1-1024 also)

So just make sure that your pc has this ip, its better to set it manually:
IP Address:192.168.2.10
Subnet Mask:255.255.255.0
Default Gateway:192.168.2.1
DNS Servers:217.27.32.196 and 217.27.50.125

If you need more than one pcs to have open ports then you can put your own router after the modem with the ip 192.168.2.10 and then from your router forward again the ports to any ip that you need