Re: Multi-Networking in Linux - Multiple Subnets

On 7/31/26 00:06, Robert Riches wrote:
> On 2026-07-31, c186282 <[email protected]> wrote:
>> On 7/30/26 17:18, Lawrence D’Oliveiro wrote:
>>> On Thu, 30 Jul 2026 13:58:28 +0200, Carlos E. R. wrote:
>>>
>>>> The ISP configures the router so that it is mandatory to use
>>>> 192.168.1.*, and they take a good chunk of it for their own usage. I
>>>> have no recourse but using this non standard network.
>>>
>>> I remember seeing one setup -- I think in the house of a friend of a
>>> friend -- where there, not one, but *two* routers between the house
>>> LAN and the Internet. The outer one specified one private LAN, while
>>> the inner one put the house machines on an entirely different one.
>>
>>     TWO routers ? UUUGGGH !!! Sounds like
>>     a world of trouble !
> 
> Sounds can be deceiving.  If the routers are arranged in series,
> you get what is sometimes referred to as double-NAT.  You end up
> with three levels of network:
> 
> - outer WAN with IP address provided by the ISP
> 
> - middle ground, LAN to the outer router and WAN to the inner
>    router
> 
> - inner LAN
> 
> A host in the middle ground can access the rest of the middle
> ground and the outer Internet.  The middle ground can be used for
> less-trustworthy machines, like an employer's laptop or other
> Windows machines.  It's somewhat like a DMZ.  If printers must be
> accessed by the employer's laptop or other Windows machines, the
> printer can go in the middle ground.
> 
> A host on the inner LAN can access the rest of the inner LAN, the
> middle ground, and the outer Internet.  For an intruder to attack
> a host on the inner LAN, the intruder needs to break through both
> routers.
> 
> Zoom and a few other services don't play well with double NAT, so
> Zoom and the like bad-mouth double NAT.  If I ever really need to
> use Zoom, I'll use it from a Raspberry Pi in the middle ground.

   Well, I'm not corporate-funded anymore and
   there's no clear approach to multiple routers
   on my home 5G connection.

   Likely what you say CAN be done ... but .....

   So, I'm looking for a "good cheat".

   Someone suggested altering the netmask in
   the device def ... make it 'broader'. MAY
   be that might do something.

   Or maybe create a gigantic clusterfuck.

   In any case, the "IOT" world is sucking
   up lots and lots of addresses. Depending,
   254 may NOT be enough, or at least be
   enough to create a horrible clutter you
   can't manage or organize. I'd LIKE to push
   all my "IOT"-type devices off into a different
   subnet YET be able to GET at them easily.