Just checking to see if an assumption I’ve been operating under is true.

How does network traffic flow with switches? Let’s say I have two switches connected to the switch built into my consumer grade router that assigns IP addresses to the devices on my network. Attached to each of the two switches are two computers, four total, and I’m copying data from one computer attached to the a switch to the other computer attached to the same switch. Does the data being copied go from the first computer through the switch to the second computer? It doesn’t go through the router at all, correct?

I’m asking because I’m wondering how the data from my security cameras attached to my NVR attached to a switch on my network flows. My assumption was the data stays between the cameras and NVR a d doesn’t mess with other traffic on my network.

Assuming your connection is like this:

device01 -- switch 1 -- router -- switch 2 -- device 2, then yes, packets/frames flow through the router

if your connections are like this:

device1 -- switch1 -- router -- switch2
              \-- device2

or this:
device1 -- switch1 -- switch2 
              \--router   \-- device2

then, no, packets do not flow through the router. This assumes that the devices are both numbered in the same IP subnet, and have a MAC - IP mapping for the other in their ARP table.

There is still some interaction with the router for both devices when they pick up their DHCP lease, but after that, they talk directly to each other. That's the difference between a network, and an internet.

The router can be left out of the last two diagrams if manual address configuration is used on the end devices instead of DHCP (some switches provide a DHCP server as well).

Of course, only one device on a single ethernet can "talk" at any given time. Switches (as opposed to hubs) are able to provide multiple ethernets (created as needed between a device on one port that sends a packet to a device plugged in to another port). Ethernet broadcasts, used mostly for device discovery, tie up all active ports on a switch as do (most) IP broadcasts and multicasts. So your assumption about camera<->NVR traffic may or may not be valid, it depends on the gory details of how they communicate. I doubt the data rate is sufficient to cause congestion on a 100baseT network, but on older technologies, there is a lot less head room.

For purposes of clarification the LAN ports on the router are just another switch.
Routing implies communication between different networks (subnets).

If you want to know how data moves on an Ethernet network look up CSMA/CD.

Also switches use a Mac Address system to identify traffic flow as opposed to the now very old hubs that previously forwarded traffic to every port.

Thanks guys. That’s what I thought, a switch would create a direct connection between two devices connected to that switch with no interaction with other devices except for getting IP from the DHCP server.

While the eight cameras I have wouldn’t push the limits of 1000BASE-T, full backups of individual computers to an NAS would. Keeping the computers and NAS on a separate switch from the cameras and NVR would be a wise move.

Hubs and Tolkien rings, one ring to rule them all!. Sorry, hubs and token rings were where all data followed specific paths and each device had to wait its turn back in the olden days. Switches changed all that.