I have setup to forward port 23 to an internal server - it connects through, OS is displayed, but the server does not give me the telnet login.

It works internally and externally with a different router.

Do i need to do something else on the 2820?

Thanks

As with other issues concerning port 23 (and ports 21, 22, 80 and 443), the Draytek comes with remote management enabled by default (a dumb decision, IMO), so the Draytek listens itself on these ports. You need to turn off the 2820's remote management (or at least the remote Telnet management), via System Maintenance -> Management.

thank-you i will give that a go.

It doesn't have remote management enabled by default, just that the management ports are the same on both LAN & WAN interfaces, so even with remote management disabled the router will still be listening on those ports before it allows port forwards through.