I am trying to help two friends. One is on a home cable/DSL network with ports 25 and 80 blocked. The second has a T1 and offered to allow the home user access to redirect port 80.

We have all searched, but are still unclear what the zone file for DNS on the T1 host should look like to make this happen.

A zone file have been created for the home cable user's domain on the T1 host, but we are not certain how to create the A/SRV/CNAME records that will cause http://domain.com:8080 to be redirected to http://domain.com.

Could anyone point to where there are guidelines or rfc docs that explains what to do.

Thanks

You cannot do port translation with DNS. Redirecting port 80 (because http://domain.com is the same as http://domain.com:80) to port 8080 must be done some other way.

Off the top of my head, you could have the A record of www.domain.com point to the T1 host's IP address. The T1 host could run a webserver and the index.html for www.domain.com would be a redirect to www.sub.domain.com:8080. www.sub.domain.com would have an A record that pointed to the broadband network.

Thanks for your reply. I am just curious, do you think that the solution that you proposed is the same that sites like no-ip or dyndns offer?

When I read these sites faqs I got the distinct impression that their solution for home users was some DNS magic that I could not understand.


Again, thanks.

What the sites you mentioned do is direct the traffic to themself, then have a reverse-proxy running to send the traffic to your HTTP server on a different port. Of course, you could do the same thing by using mod_proxy on the T1 host instead of simply using an HTTP redirect.

Proxying is more transparent and will work for a lot more different types of web apps, deep links, etc, but it also requires that all the traffic goes through the T1 host first before it reaches you. With a redirect, only the first request goes to the T1 host, after that they're on your page and all the requests go directly to your server.

Thank you so much for your response. I have been reading and pondering the mystery of what those services were offering for a very loooooong time!

Again, my deepest thanks for your patient and time.