Differences between two ethernet connections via router ports vs. two connections via network switch?

This is the difference between layer 2 and layer 3 depending on the router and the mode it uses for extra ports.

Assuming each port on the router is configured to be a separate subnet (layer 3) then rules must be created to allow traffic on interface 1 to talk to traffic on interface 2.

Some routers will have 1 port be an uplink to WAN (eth0), and all other ports be bridged effectively making them a switch (layer 2). This is not usually preferred because the router has enough to do processing packets and forwarding them on to their destinations.

The network switch allows devices to find each other by their MAC address. Where the router functions by IP address.

Fun experiment: if you have a managed switch, enable port mirroring and plug in a computer to one port, and another computer running wire shark into the mirrored port. You'll get a really interesting picture of how noisy a network can be with all the broadcasts, SYN, ACK, SYN-ACK, and if you have Apple devices - the bumload of traffic from mDNS.

/r/networking Thread