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I have a domain using CloudFlare's DNS, I want to make it redirect to my server's IP (dynamic IP, port 21 blocked by ISP) which at the moment uses a No-IP DNS.

The current setup is that I have a subdomain as a CNAME targetting the No-IP domain, but that only works for things like the Minecraft server (which looks for a set port that isn't blocked by my ISP), and I'd like a solution that lets me redirect port 21 from the CloudFlare domain to port 2121 on the No-IP domain, or something else that points to my dynamic IP, where an FTP server is already set up and running.

I've had SRV records mentioned to me but without any further help, and it only made me more confused. Thanks in advance for the help.

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You would need a proxy to do this. – David Schwartz Jul 2 '13 at 21:54
up vote 1 down vote accepted

DNS is a name to ip address resolving service not a port redirector

SRV helper records can send traffic to a specific host based on destination port but not do port redirection.

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I see, so apparently the SRV record is working, it's just that (most) browsers don't support it... – Svetlana Jul 2 '13 at 22:00

dyndns has a nice port redirection service. You run an agent on your server that will update the DNS in when your IP changes. Publicly you ftp to port 21 but it will redirect you to 2121. You will need to open port 2121 on your ingress FW.

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Dyndns is paid though, apparently there's no free solution.. Getting a package with my ISP that gives me static IP + ports 21 and 80 open is prohibitively expensive, so I'm not doing that. I'll keep asking people to use :2121, then, but thanks for the help. – Svetlana Jul 4 '13 at 1:21

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