[CentOS] "new" computers and monitors

Thu May 29 13:19:03 UTC 2014
Johnny Hughes <johnny at centos.org>

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:
>>>>>> Until recently, I had a 32-bit machine with one monitor running fedora.
>>>>>> 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?
>>>>>> The answer I am expecting is one or more links to tutorials or the like.
>>> It can get fairly "interesting" depending on what you are trying to do.
>>> You may need a special crossover cable to connect the two computers
>>> directly.  The newer network cards may be able to handle doing this with
>>> a standard cable, but I haven't tried it.
>>>
>>> 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.
>> I don't know that I do.
>> I've not done anything with a router since connecting
>> my old computer to CenturyLink's router/modem.
>>
>> 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.
>
> Consumer grade Internet connections only give you a single global IP 
> address, so anything connected to your router will use that same IP 
> address globally.  The router will do NAT and DHCP for the internal 
> machines to give them a local address.
>
> (I am assuming that you have a standard modem/router combination that 
> does NAT/DHCP.  As Les mentioned, if you have a simple modem that 
> connects to your computer without the built-in router, things will be 
> more complicated.)
>
> Windows will fetch a local IP address (as will Linux) unless you specify 
> one yourself and disable DHCP.  The Windows and Linux OS's on the same 
> box may or may not automatically get the same local IP address depending 
> on how the router handles it.  What is your concern about the IP address?
>

This is NORMALLY true ... although some ISPs provide multiple real IP
addresses too.

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.

However, routers can be set up differently ... so the router's manager
(be that you or your ISP) should be consulted WRT the router setup :D


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