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Re: Simple Linux to Linux(Debian) email

On 2019-04-12 10:57, Dan Purgert wrote:
mick crane wrote:
On 2019-04-11 17:16, mick crane wrote:
On 2019-04-11 17:05, Greg Wooledge wrote:
On Thu, Apr 11, 2019 at 05:02:46PM +0100, mick crane wrote:
I think that is what dynamic ip address services do, change the
but the service has to be on the ISP's router ?
Do I understand correctly then when your isp/home address changes
your box
broadcasts its domain new address to the internet ?

It doesn't have to be on the router. You can set up a hook in Debian
to run an arbitrary command whenever your IP address is changed by
This hook receives the old and new IP addresses, and some other
as environment variables.  It's about 3 lines of code to set it up.
parsing of the output of any ip or ifconfig command is needed.


I'll have a read but there must be something I don't understand.
Thought there was a hierarchy of domain names mapped to ipaddresses
that all the different servers can query as to where something is.

Ok I think I see, you can host your own domain if you have a fixed
ipaddress but if have ipaddress that changes need to register domain
name and have company host it and advertise they know where it is but
can change the nameservers for the domain from theirs to yours at
changed ipaddress.
You can't willy nilly broadcast any domain to the internet yourself.

Well, once your domain is registered (for example, mine), you can either

1. give your registrar the IP address they should point the domain to.
      This is easiest with static IP address assignments from your ISP,
      but there's no reason you couldn't do it on a dynamic IP


  2. Use a dynamic DNS provider (e.g. dyndns, no-ip, afraid, many
      others), and have them automatically update the DNS registration
      when your IP address changes.

Note that for option 2, you tell your registrar to use those other
nameservers, rather than their own.

I use option 2 myself, registered via ... oh I think 1&1 ... but using
no-ip to provide my dyndns (although the IP hasn't changed in well over
a year - I still don't want to be caught unawares :) )

I thought those dynamic dns services offered a sub domain of their own domains. Can you have any registered domain point to dynamic dns servers and them redirect it ? I have wondered what they do to stop people broadcasting their own top level domain.
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