Re: Multi-Networking in Linux - Multiple Subnets

c186282 <[email protected]> writes:
> On 7/30/26 00:14, rbowman wrote:
>> c186282 wrote:
>>> Has anybody made this work ? The adapter must not see just ONE subnet,
>>> but a LIST of subnets and translate one to another seamlessly.
>>
>> Many of our sites used dual homed NICs. Typically one NIC would be on
>> the LAN, the other would be on the state network. In Windows the
>> route command lets you set up a persistent route so that traffic goes
>> through the correct gateway.  You can do the same thing to establish
>> a failover with redundant networks.  I don't know if that is what
>> you're asking.
>
> I don't want "FAIL-over" - I want two or more
> subnets to be "live" ... access machines/devices
> on several subnets just by supplying the correct
> dot address or such.
>
> Preferably some fix that does NOT require 9999
> line scripts or $500 hardware.

If you want multiple IP networks on the same ethernet network, you can
add multiple address/mask pairs to the ethernet interface on each device
that needs to be on both. Just read the docs for whatever system you use
to configure the network.

However you will need some way to make all the other devices pick the
right network to be on. That means either manually configuring them
(which could be impractical many cases) or configuring your DHCP server
to assign addresses appropriately. Really, I don’t think is a great
idea, unless you have very simple requirements it’s more work than it
sounds.

My strategy is a separate VLAN for each device class, with a separate
SSID for each VLAN and with most physical ethernet ports assigned to the
VLAN for the attached device. Devices on different VLANs can only
communicate with each other if the house router permits it.

> Not TOO long ago, we'd have asked why anyone would need more than 254
> IP addresses easily in grasp. However that was before MANY boxes, MANY
> servers and finally "IOT".

If the problem is too many devices, just use a bigger network, there is
no reason you have to limit yourself to a /24.

-- 
https://www.greenend.org.uk/rjk/