Multi-NIC Multi-Network Configurations in MATE 17.04

I have two networks in my home. Subnet #1 Gateway 192.168.1.1 is connected to the internet. Computers, phones, tablets, movie streaming devices connect here. Subnet #2 gateway 192.168.2.1 is for private computing, on which a NAS houses all personal and business files. The computers are connected to both networks to allow working with personal and business files as well as internet.

Both PCs have the Multi-NIC Multi-Network capability configured and working in Windows 7. Both computers are being migrated to MATE 17.04.

When MATE 17.04 auto-configures the network connections the status bar in the upper right appears as:

The depicted auto-configration results in no internet access on subnet #1 and ready access to subnet #2 for personal and business files. Again, the desired outcome being: Access to both internet services and on subnet #1 and files services on subnet #2 simultaneously.

Is there a way to use the GUI Network Configurator to configure a Multi-NIC Multi-Network system?

The forum will not allow a new user to insert a second image into a post.
This was to be a screenshot of the MATE 17.10 Network GUI Configurator
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As an alternative I tried using the interface file settings I used successfully some time ago when demo'ing MATE 15.10 in December of 2015. The result in MATE 17.10 was that the interface file settings worked initially without reboot by stopping and starting network service manually, but when the MATE 17.10 system was restarted the settings no longer worked.

/etc/network/interfaces

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

# J5 Create USB/Ether Adapter MAC c4b
# MATE Identifies as: ASIX Wired Connection #2
# Subnet One Internet Gateway 192.168.1.1

auto enx00051ba184cb
iface enx00051ba184cb inet dhcp
metric 10

# Ethernet internal port on Sager laptop MAC 254
# MATE Identifies as Realtek Wired Connection #1
# Subnet Two Computing Gateway 192.168.2.1

auto ens2
iface ens2 inet dhcp
metric 100

I have no way to simulate your situation, so this is all “guesswork”. It’s what I would do.

First of all: I would name the connections. “NAS” and “Internet”, for example, instead of “Wired connection 1” and “Wired connection 2”. Also, make sure you have restored the original /etc/network/interfaces file, if you experimented with it making manual edits (or any other files you have edited manually).

This is all done in Network Manager’s Edit connection interface (the image you were not allowed to include in your post).

Both connections: make sure you have “Connect automatically” set on both.

On the NAS connection (192.168.2.1): go to the “IPv4 settings” tab, press “Routes” button and tick “Use this onnection only for resources on its network”.

That’s it, for the “easy fix”. Restart NetworkManager or reboot.

Did it work? If it did - great! If not, I recommend using static IPs, if at all possible. Then you can set address, netmask and gateway in the connection settings and not use DHCP (automatic settings). All this in NetworkManager’s GUI, no need to hack config files in terminal. And “Use this connection only for resources on its network” ticked in the NAS connection settings.