How to connect ftp from outside router in centos

have you tried to assign a static IP to your FTP server, a port forward to the FTP server in your router.

you might have a problem so since most ISP block ports so people cannot host web and FTP servers from home.

you could try using outside port 9021 and forward it to internal port 21

to access it from the out side you would your public IP:9021 or (if you have) DynamicDNS:9021