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
Sent: Sunday, February 01, 2009 3:31 PM
Subject: Re: 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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