[CentOS] "new" computers and monitors

Thu May 29 14:39:45 UTC 2014
Johnny Hughes <johnny at centos.org>

On 05/29/2014 08:34 AM, m.roth at 5-cent.us wrote:
> Johnny Hughes wrote:
>> On 05/28/2014 02:26 PM, Bowie Bailey wrote:
>>> On 5/28/2014 3:00 PM, Michael Hennebry wrote:
>>>> On Wed, 28 May 2014, Bowie Bailey wrote:
>>>>
>>>>> On 5/28/2014 1:29 AM, Michael Hennebry wrote:
>>>>>> On Tue, 27 May 2014, John R Pierce wrote:
>>>>>>
>>>>>>> On 5/27/2014 5:38 PM, Michael Hennebry wrote:
> <snip>
>>>>>>>> The later editions of fedora didn't like it, so I switched to
>>>>>>>> CentOS. Now I have two 64-bit machines and two monitors and a
> CenturyLink
>>>>>>>> router. Also a KVM switch that I have not taken out of the package.
>>>>>>>> My main machine has two video connections and two ethernet
> connections,
>>>>>>>> eth0 and eth1 .My secondary machine sometimes runs Windows,
>>>>>>>> so I'd like it not to have its own global IP address.
>>>>>>>> My first thought would be to connect it directly
>>>>>>>> to one of the ethernet ports on my main machine.
>>>>>>>>
>>>>>>>> How do I go about this?
> <snip>
>>>>> Why do you want to connect the two computers like this?  It is usually
>>>>> more trouble than it's worth unless you want to use the first computer
>>>>> as a firewall or something.  Just connect both of them to your router
>>>>> and everything should work fine.
> <snip>
>>>> I want the second computer to not have its own global IP address.
>>>> It will at least occasionally run Windows.
>>>> I'd prefer not to assume that Windows will
>>>> not try to fetch an IP address behind my back.
>>> The router should have a built-in switch with multiple network jacks.
>>> Just plug the new computer into the router along with the old one and
>>> you should be fine.
> <snip>
>> This is NORMALLY true ... although some ISPs provide multiple real IP
>> addresses too.
> AFAIK, not unless you pay extra.

Well sure.  But an ISP can provide you with a router that puts all the
machines directly on the Internet with a global address.  Since the OP
did not seem to know how the router is set up, all I said was to verify
how it is set up.  It would not be a "Good Thing" to plug a default
install of a Windows box into a router that is not also providing
firewall features of some kind.  While this is not the "normal" (or if
you prefer, most common) ISP setup ... it is certainly a plausible
setup, so one needs to understand what their ISP is providing and  do a
proper setup.  We should not just assume (hahaha) that the ISP router is
sent with the most common setup, we should check :)

>> It is easy enough to test though ... plug in the computer that works,
>> look at its IP address, if it is in the private range (192.168.x.x,
>> 10.x.x.x, 172.16..x.x to 172.31.x.x) then the provided router is
>> isolating the real IP on the outside port.
>>
>> It is also then also normally true that internal ports are NAT'ed and
>> isolated from the outside world.
> <snip>
> I was under the impression that the OP actually doesn't want it visible to
> the world, isn't intending to browse or email via it, but that it was for
> *only* inside. IF that is the case, he'd have to go into the router and
> tell it to assign it an internal IP, and to *not* NAT it.

WIthout some type of NATing (if you have an internal IP) it can not
touch the Internet .. makes reading email kind of hard :D
(I did not say direct NATing .. some type of NAT is how things have an
internal address and talk to things that have a real address somewhere else)

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