But the whole point is, as Andrew said, you don't need to port forward. You're looking for the wrong thing.
Your 8 IP addresses exist on the Internet - They're publicly accessible - That's the point of having them! Port forwarding is used with NAT (or more correctly, PAT) where the router doesn't know which non-public address to forward access to a port. In your case, the IP address is explicit, as it's public.
I've no idea why you used port forwarding with the Draytek, other than perhaps the forwarding rule was ignored but coincidentally opened a firewall?
As Andrew said, look at firewall configs... Or alternatively, release your block of 8 addresses and revert to a single address and NAT/PAT as it sounds like you can't really justify having your /29?
Thinking further, if you have a /29 that has .16 and .22 within the subnet then .16 is the network ID so can't be used. The usable addresses are .17 to .22 with .23 as the broadcast address.
Edited by ferretuk (Wed 26-Apr-17 22:53:17)