Dynamic DNS issue

Daniel Rudy 5n6o7.8d9c0r1u2d3y4.5s6p7a8m9 at 0e1m2a3i4l5.6p7a8c9b0e1l2l3.4i5n6v7a8l9i0d1.2n3e4t5
Tue Jan 4 08:29:11 UTC 2005

At about the time of 1/3/2005 4:56 PM, Kevin Darcy stated the following:

> Daniel Rudy wrote:
>>This is more of a how-to question than anything else.  Basically, I have
>>two consumer xDSL lines at different locations that I want to be able to
>>have the computers find each other.  The DSL lines are PPPoE with
>>dynamicly assigned IP addresses.  The only thing that is constant is the
>>hostnames which are registered with a dynamic DNS service and are
>>available across the internet.
>>Now my question is how to I setup the servers at each location so that
>>they update each other's DNS information?
> I guess I don't quite understand your question. If both boxes register 
> themselves in DNS, and Machine A can resolve the IP address of Machine B 
> by its name, and _vice_versa_, then why do you need to do anything more?

Because both locations have master DNS servers that administer the same
domain name.  How do I tell the DNS servers that the IP address of the
other machine has changed?

> If the propagation time for the changes is intolerably long, I suppose 
> you could run a couple of local caching nameserver/resolver instances on 
> each box, one with a low max-cache-ttl, e.g. on the order of seconds, or 
> a low number of minutes, in order to keep things dynamic, with the other 
> instance selectively forwarding to it (selectively, because you wouldn't 
> want _everything_ you look up to be that dynamic). Note that I've never 
> actually tried such a setup, but it should work in theory. You might 
> want to first check with the dynamic DNS service to ensure that they 
> don't have a problem with you -- and everyone else with the same idea -- 
> hammering their nameservers like that.

What I was thinking was that if I have zone transfers only when the IP
addresses get updated, it would not be too much of an issue.  The server
who's IP address has changed knows what the other IP address is.  If the
update failed, then the only other thing to do is if the transfer
failed, then do a lookup on the DDNS provider.

That's why I'm thinking of using nsupdate to do this from inside a script.

> Or, alternatively, just bite the bullet and get static IPs.

Static IPs are not really available, at least not cheaply.

> - Kevin

Daniel Rudy

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