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From "Michael Rogers" <mich...@michaelsrogers.net>
Subject Re: [users@httpd] Re: Help - Name Server - Maybe
Date Mon, 02 Feb 2009 12:05:20 GMT
Eric:

My email utility sent you to the junk mail folder and I didn't see you until now.  Next I
am suffering this morning from severe pain and the morphine is not helping so I may not respond
back right away.  My pain may be for a couple of hours or in might be for days.

I do know that my computer works with IP address and not names.  I know that I am having a
router problem.  some that are helping here can get to my modem but that is as far as they
get.  That's the problem that I need to resolve.

Right now the machine that has the Apache on it has an IP address of 10.0.0.115.  I found
the host file.  Am I to understand that I should put 10.0.0.115  www.michaelsrogers.com in
the file right under the 127.0.0.1  localhost
  From: André Warnier 
  Sent: Sunday, February 01, 2009 3:31 PM
  To: users@httpd.apache.org 
  Subject: Re: [users@httpd] Re: Help - Name Server - Maybe


  Eric Covener wrote:
  [...]

  > 
  > FWIW It's quite common to not be able to access your webserver with
  > it's external IP address from within your LAN.
  > 

  Allright, I'll try to help.  This has not much to do with Apache, and 
  more with basic TCP/IP.  So let's start at the beginning.

  First your internal LAN.

  I) computers work with IP addresses, not with names.  That may surprise 
  you, but it is so.
  When you tell your browser to get "www.google.com" :
  - it first looks in its own local "hosts" file to see if there is a 
  translation for "www.google.com" into an IP address like 1.2.3.4
  The local hosts file can be found :
  under Unix/Linux, in /etc/hosts
  under Windows, in windows\system32\drivers\etc\hosts
  - if the local hosts file does not provide a translation, then your 
  browser asks "the DNS system".  That is something complicated, but 
  basically it means that it will need the IP address of another computer 
  known as a DNS Server, and it will send a message to that IP address, 
  asking for the IP address of "www.google.com"
  - if the browser cannot find finally an IP address for www.google.com 
  with any of the above, it gives up and tells you so.

  II) where your local computers get their own IP address :
  there are 2 ways :
  - either they are set up with a fixed IP address
  - or they are set up to ask a DHCP server to give them one. For this 
  second possibility, the computer (usually when it starts), sends a 
  special "broadcast" message on the local network, asking if a nice DHCP 
  server would please give them a new IP address.  If any DHCP server is 
  listening on the local network, it will consult its internal tables to 
  see which address it could give (it has a range of addresses), among the 
  ones which are still free (if it has already given an address away, it 
  will not give it away a second time).
  That is why, when you turn off your DHCP server, your stations are not 
  working anymore : because they are set up to request an IP address from 
  a DHCP server, and there is none active, so they don't get one.  And if 
  they do not have an IP address themselves, they cannot use TCP/IP and 
  thus their Internet access doesn't work anymore.

  III) A workstation can use a variable IP address given by a DHCP server, 
  but a server should have a fixed IP address.

  That is because for a workstation it does not matter : nobody will try 
  to find it, it just needs to find the others.
  But for a server, it's different : other stations need to find it, so it 
  better have an address that does not change all the time.
  (For the same reason that you can make a phone call to someone else from 
  any phone, but if someone needs to reach you, they need your number).

  A part of your problem, is that you are trying to turn a workstation 
  into a server (an Apache server).  So you have to stop it from getting a 
  variable IP address, and give it a fixed one.
  But, you have to pick an IP address which on the other hand, your DHCP 
  server will not give away to someone else.
  (Because two stations having the same IP address confuses everyone and 
  does not work).
  So you need to look in your DHCP server which range of addresses it is 
  giving away, and pick one outside that range (just add 1 to the last 
  number in the DHCP range).(at the end, not at the beginning).
  (If your DHCP server is also your router, it may have a web interface to 
  make it easy.  If it is not the router but some server, then this may be 
  more complicated).
  Now when you have done that, try from another station to access your 
  Apache server at the fixed IP address that you gave it.

  For example :
  - suppose your DHCP server is programmed to give away addresses in the 
  range 192.168.1.100 - 192.168.1.150 (51 addresses)
  - suppose then that you gave your Apache workstation the fixed address 
  192.168.1.200 (to be well outside of the above range).
  - then try "http://192.168.1.200" (from another internal station)

  If you get a response from Apache, then we are already well on the way.

  Next, we want all the internal stations to be able to access this Apache 
  server, not by IP address, but with a name.  That is easier for humans.
  Read Chapter I above, again, to remember how they do that.

  Unfortunately, there probably isn't a DNS server on your local network, 
  that could be used by the internal stations.
  Thus you will have to use the "hosts file" method.
  On one of the workstations, locate the hosts file, and add the following 
  line in it :
  192.168.1.151 some.nice.name
  then close all browser windows on that workstation, re-start the 
  browser, and type "http://some.nice.name".
  If everything worked according to plan, you should get the same Apache 
  page as before.
  Now do the same on all the other workstations, et voila you have an 
  internal webserver. (You might want to find a nicer name than 
  "some.nice.name", like "www.apache.local" e.g.).

  In the next installment, we'll look at the external access to your 
  webserver.


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Michael S. Rogers
(406) 967-2385

Web Sites: http://www.michaelsrogers.net & http://www.michaelsrogers.net/trainwreck/Wreck.html
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