(Oops! Sorry, I sent this initially without the proper subject; I guess it
may or may not have bounced at the list manager.)
Trishan Arul <[EMAIL PROTECTED]> wrote:
>
> Yep, that's it. It's not really the hub that is 'allowing' one computer on
> at a time. Its his ISP that only allows one computer to have an IP address
> (which is typical). To be honest, I'm still not sure how the world has
> still not run out of usable IP addresses yet, even with most users using
> dynamic addresses.
>
>> From: Amber Rhea <[EMAIL PROTECTED]>
>>
>> Why would the Asante hub allow the computers to access the internet only one
>> at a time? We have a Linksys 5-port hub, with all the computers and the
>> cable modem plugged into it, and the computers all have simultaneous access.
>> Is the difference that we have a Linux server, and in the above situation
>> there was no 'router' until the Asante router/switch was added?
My ISP gives me only one IP address, dynamically, at a time. That's all I
pay for. This address is in the "168" series. With a hub, that IP address
is used by a computer that has the proper TCP/IP setup to work with a DHCP
server, in this case, the ISP; a hub doesn't know the difference. Since the
ISP knows only that one computer, another computer on the hub cannot be seen
by the ISP. With the router, the one IP address, sent dynamically by the
ISP is given to the router which has its own "MAC" address (not Macintosh,
every ethernet card also has a "MAC" address). A router, which is usually
also a firewall, assigns to each computer on the local area network (LAN)
another address, this one in the "192" series. The computers or servers on
the outside know nothing about the computers or servers on the inside. The
router handles the traffic coming and going between the two worlds.
In the outside world, I believe Thishan is correct in that a particular IP
address can exist only once at any one time, no duplicates, even in the
dynamically assigned groups. In the inside world, any LAN using the "192"
series can have addresses duplicating those in another LAN without
confusion.
In Amber's case with the Linux server, I'd wager that the server is acting
precisely as a router and perhaps even has a software firewall. It
possesses a "168" address for the outside world, whether a static address or
a dynamic one assigned by the ISP. And it, in turn, assigns dynamic "192"
addresses to the other computers in the building, or someone has tediously
assigned status "192" addresses to each computer. Another possibility is
that Amber's ISP has assigned separate "168" addresses for each computer.
One could check the TCP/IP control panel of each computer to investigate
this.
A number of web sites that give much more detail include:
http://www.knowledgehound.com/topics/networks.htm
http://www.threemacs.com./network/index.html
http://www.vicomsoft.com/
http://www.mac512.com/appletal.htm
http://www.farallon.com/
http://www.asante.com/
By the way, I'll be away from this list for a week or so.
--
Al Poulin
--
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