[AMRadio] Re: New IP address


Bob Bruhns bbruhns at erols.com
Thu Jan 31 14:46:16 EST 2008


This is an example of the difference between 'fixed IP' ad 'static IP'.

Most home users and many business users have dynamic IP, which is assigned when they log in.  But a website, for example, needs a
fixed IP address, because the whole internet domain name system pretty much requires it.

When we go to a website, our browsers check with a doman name server to find the IP address of the site, and then they go to that IP
address.  If you know the IP address, you can type it in directly, and that usually works too.  Exceptions are websites that share
an IP address, and these need to know which website you want.  Evidently the browser includes this information in its packet header,
and it may actually come from the nameserver.  I had a nameserver issue once where the nameserver did not provide this info, and I
had to change nameservers to get my bruhns.us website to work.

If the IP address of a website changes, the primary domain nameserver for its domain has to update its information, and then it
takes a day or two for this information to propagate around to the nameservers on the whole internet.  This is why a change in
web-hosts can cause a day-long outage for a website, followed by a sporadic recovery, and it is also why a website starts up
sporadically in a similar fashion, and why a new mail domain goes through the same problems, etc.

The IP addresses are assigned in blocks to ISPs.  When ISPs change hands, these blocks get shuffled around, and all sorts of odd
things happen, such as changes in website IP addresses and day-long service outages.  It is best, if this will happen, to host the
site at both IP addresses for the transition if possible, although this can cause headaches for sites that need high security, or
sites that provide unusual services.

   Bacon, WA3WDR


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