Connect 2 Computers w/Ethernet Cable
 

How do I get the connection to work? I tried both an Ethernet cable and a Crossover Ethernet cable. 2006 Dell Laptop to 2011 iMac. I failed using Warpinator which does work on my wireless LAN. Both run Linuxmint 21.2 Cinnamon.

Will any commands I use have to be undone when I revert to wireless?

Connect the two ethernet ports.

On one computer, disable WiFi and set the wired connection to "Automatic (DHCP)".

On the other computer, set the wired connection to "Shared to other computers".

After you're done, re-enable WiFi on the first computer.

I do not see any DHCP. There is MTU w/automatic for in the wired connection page.
There is no Shared to other computers

in general you only need to connect the two ports, as it was mentioned. But you need to configure the two hosts to be able to use this setup.
this is a guide to explain that: https://askubuntu.com/questions/2283...hout-a-router/
On mint it should be something similar.

Without knowing what type of adapter is in the Dell or mac I would use the crossover cable. Use the ip command to configure the adapters. Running the commands does not make any permanent changes.

You should be able to connect them with a straight through Ethernet cable and you also can configure static IP addresses, but then you will not have host names. I'm guessing this is temporary to get data/info from one side to the other?

Under the settings, go to IPv4 settings tab. Then you will have Automatic (DHCP) and "Shared to other computers" settings.

Auto mdi-x came out in the early 2000s so a straight cable should probably work.
If you don't see a link LED illuminated on the port then try the crossover.

Can connect with either cable. The port on the 2006 Dell laptop lights up w/either cable when connected to the other computer a 2011 iMac. There are no lights on the iMacs Ethernet port. On the Dell the Ethernet port left light shines steadily, the right one flickers dimly.

The left should be the link LED and right show data activity. Assign IP addresses to each interface and you should be good to go.

On iMac: sudo ip addr add 10.0.0.1/24 dev enp2s0
On Dell laptop: sudo ip addr add 10.0.0.2/24 dev eth0

IPv4 set to Automatic (DHCP) on both
Routes section of IPv4 page has Network, Netmask, Gateway and Metric fields that are not filled in.

Still get Connection Failed.

Wireless is not enabled when attempting wired connection.

Strange, With Mint 21 I would not expect the ethernet adapter to be named eth0 unless you disabled naming conventions.
No need for DHCP since you are manually configuring the adapters.
Route should not matter since you are direct between the two computers.

from the Dell
ping 10.0.0.1 fails?

Also from the Dell
ping 10.0.0.2 successful?

Uhh ... I explained already.

One one computer, set to Automatic (DHCP). (The one with WiFi disabled.)

On the other computer, set to "Shared to other computers".

You need one of them to be "Shared to other computers" in order to make it share its internet connection with the other computer. That will configure a simple DHCP server as well as routing to share its other connection with the client computer.

If you go that route with the interface set to "Shared to other computers" as posted dnsmasq is automatically configured to assign IP addresses via DHCP. The host will be 10.42.0.1.

I do not see a "Shared to other computers" setting. I currently have both set to Automatic (DHCP)

I do see a Manual and a Link local only. Does that mean "Shared to other computers"