Using a switch vs router's ethernet ports

[JamieBritain101]

Someone today told me that using a dedicated switch connected to one of the router's ethernet ports is better than using the inbuilt ports on the router as it helps the router. They were telling me that it keeps the routers CPU usage lower as the switch does the routing for the connected devices which means the router only has to handle WiFi.

Is this at all true?

 

 

Thanks

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[Oshino Shinobu]

Technically, it is true. However, unless your router's CPU is exceptionally weak or you're constantly bombarding the ports at maximum bandwidth, it shouldn't actually impact performance much, if at all. Considering the majority of routers have 4 LAN ports, even using all of them at once really doesn't take up that much processing power. 

 

I could only see it becoming a potential issue if you have a gigabit internet connection. In that case, it may well be better to use the switch to hand the load off. 

[jared404]

In theory yes there is a small difference. This will only make a difference if you are making large file transfers between two devices on the local network and both are connected to a switch vs a router. These kinds of tasks don't have much of a load on the router anyways. You are better off connecting everything to the existing router because adding the switch may introduce a few more milliseconds of latency.

[brwainer]

Most SOHO routers have a 5-port switch chip inside of them, the same chip that you would find in a cheap unmanaged 5-port ethernet switch. One port connects to the CPU and the others are your 4 LAN ports. The CPU (really an SoC) in turn actually just has a few ports, one for WAN, one to connect to the switch chip, and then whatever wireless they are using (almost always 2.4GHz is builtin to the SoC but 5GHz may be another chip that is connected by PCIe or USB internally).

 

Assuming your router is designed like this, LAN transfers actually just go through the switch chip, and the traffic never hits the CPU of the router. So attaching a seperate switch in this case doesn't do much, it really only helps prevent a tiny extra bit of heat generation that would happen in the switch chip.

 

Routers that have every port attached directly to the CPU are much more expensive, and even then usually can't do switching at "wire speed" e.g. at a full gigabit, especially if you are using small packets (under 500 bytes) instead of large ones (1000-1500 bytes, or Jumbo frames which are 1500-9000 bytes). This means there is a simple way to test: Do a file transfer between two LAN computers, preferably from SSD to SSD or RAM to RAM so that you are really testing the network. If you get anything over 80MB/s, especially 100+MB/s, then the router has a switch chip inside for the LAN.