Web hosting, DSL, and domain names

[blu at vl.com (Tom Metro)]

Scott R Ehrlich wrote:
> I have a domain name registered with a web hosting provider. 
> If I were to eventually switch from cable modem service to DSL...
> would I be able to "share" my domain name and IP on my line if I
> wanted to let the hosting provider continue to host my domain name?

Domain, yes. IP, no.

As pointed out in the other response, the typical way you would set this 
up is to have the hosting provider provide DNS services, as they 
probably do currently, and the records for your web site would continue 
to point to the hosting provider's web server IP.

If you then wanted to run your own mail server off of your DSL line, 
you'd add a DNS A record for something like mail.example.com that points 
to your public IP given to you by your DSL provider. You'd then set up 
an MX record for example.com pointing to mail.example.com.

By analogy, the portion of the DNS you control is like a page in a phone 
book where all the last names are your domain. It doesn't matter who 
provides the DNS service for you. As long as you have control over it, 
you can create entries that point to any publicly reachable IP addresses.

If you had a dynamic IP address from your DSL provider, you'd probably 
instead end up using a subdomain from a dynamic DNS provider, like 
example.tzo.com, in which case you'd configure your MX records to point 
to that domain.

You can similarly add A records pointing to your DSL's public IP for 
other purposes, like hosting a development web server, etc. Having 
separate DNS entries for things like that will make it easier to move 
them to service providers in the future, if needed.


> It would be nice to start up something like Thunderbird to both read
> and send email under my domain name without a mail server
> complaining relaying is not allowed.

That should be doable independent of the above. No need to run your own 
mail server to accomplish that.

You should still be able to relay email via your DSL provider and/or 
your web hosting provider, as long as you configure your email client to 
authenticate in the way the provider requires, or the provider adds a 
rule to their server to recognize your DSL IP address.


> I do know it is possible to have multiple IPs pointing to the same host. 
> Could that work for my potential scenario?

In the scenario you describe above it isn't necessary. And what you 
really want is something similar, but quite different: hosts from a 
single domain pointing to multiple IP addresses. In other words, 
www.example.com going to your hosting provider's IP, and 
mail.example.com going to your DSL public IP.

You'd never want your host on your DSL line to use the same IP address 
that your hosting provider is using. Even if you could arrange the 
routing to happen, it would mess up your web hosting service.

  -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/