Hello
I’ve setup my dd-wrt router with a ddns service and now when I type in a browser my ddns address it opens the router settings. U can’t do much without the name and password but still it doesn’t look right to me?
Probably not a good idea if the management port is accessable remotely. Someone could hack it or DDoS it, and you'd have a problem. The purpose of setting up DDNS with your router is so that the router (instead of a device) can tell the DDNS service about a device on the router's network. So if the IP changes, then the router can tell the IP immeadietly that something changed. You shouldn't map the DDNS to your router though. Your router's local IP shouldn't change anyways, so I don't see the point. The only reason would be if you had DD-WRT running a VPN which you want to access remotely. Just make sure that only that port is available remotely.
I'm using it to access a home FTP server. Disabled the service on the router it self, but the link still access it.
According to the settings outside access should be disabled? 
Check that the DDNS service on your router is sending the WAN interface address and not the LAN address. If it is sending the WAN address and your router's config page is accessible on the WAN you need to disable that. I'm not sure how to do that in DD-WRT but there will be an option there somewhere.
Ja, nevermind it is only accessible (through the link, not just IP) when on the WiFi, if on the mobile net it's not. Thank u :-)
That's good. You probably have NAT reflection enabled which redirects local connections to the public IP address to the local IP address.
As long as you can't access it from anywhere else on the web, you're good. That's what I meant by remote access. Happy DDNSing.