will the network traffic be sent through the router?
In short, no.
The switch should keep track of which MAC addresses can be reached on which ports, and it then only sends packets out through the correct ports. There is a limit to how many MAC addresses a switch can remember, though it's usually not an issue unless you're operating extremely large networks.
Furthermore, most consumer routers are actually a switch for the LAN ports, which is then connected to the routing hardware which sits between this switch and the WAN port, so even if you don't have a separate switch, you still won't be able to control routing of packets that are directed to another computer within the LAN.
As an example, you can connect 2 computers to a switch with gigabit links, and then connect that switch to a router with a 100Mbit link, and still send data between the computers at speeds of 1Gbps. You can even disconnect the router from the switch entirely while data is being sent between the computers without affecting said data
I would like to point out that all of this becomes way more complicated once you introduce other protocols, such as VLAN tagging, but that is outside the scope of a home user simply transferring files between computers at home. This is a good primer if you're looking into that, though.
How about a switch that will allow high traffic between two PCs yet not interfere with a third that wants to get through to the router? All 3 PCs need to be on the same subnet. I basically want to keep Netflix flowing even if two other computers on the same subnet are transferring files between windows shares. – SDsolar – 2017-06-05T08:56:47.067
This is the perfect website for it. All general purpose software and hardware questions have a home on superuser :) – Darth Android – 2011-06-10T17:37:06.523
Glad to hear it :) Just with all the new sites coming from Area 51 (!) I wasn't sure – jrtc27 – 2011-06-10T17:46:00.800
If the question was about large, managed switches operating corporate networks, I'd point you towards serverfault.com, but home networking with consumer-grade routers is just fine here. And yes, all the new sites are confusing sometimes. – Darth Android – 2011-06-10T17:52:48.637
Just so everyone knows - the plan is to have at least 10 devices plugged into the switch, each of which could potentially be transferring data over a gigabit connection at the same time. – jrtc27 – 2011-06-10T17:54:44.063
1If that's the case, you'll want to verify the switching capacity of the router's backplane, since that will be handling all of the data going through the switch at once. Usually it's sufficient to support total utilization by all ports, but it's something worth looking into if the information is easily available. For example, a 24-port gigabit switch might have a switching capacity of 48Gbps, or sending and receiving on all 24 ports at 1Gbps at the same time. – Darth Android – 2011-06-10T18:08:00.767
Yeah, I'm not so fussed about the switching capacity - I am aware that it is a potential problem - I just want to avoid having multiple gigabit connections using one gigabit connection back to another switch/router thus creating a huge bottleneck. – jrtc27 – 2011-06-10T18:10:17.210