2 cables between switches = faster?

[da na]

This may sound stupid, but it is a legitimate question. 

I have two switches, an eight-port gigabit (Ethernet in from the wall) and a 16-port 10/100 (for devices that need Internet, but less bandwidth). I am a little worried that the devices on the 10/100 switch will get bottlenecked by the single 10/100 link connecting it to the gigabit switch, however. Therefore, if I just... add another cable will it be faster?

[tkitch]

it will not, you'd most likely break the network due to loopback.

 

(on high-end switches you could gang connections, but on home-grade stuff, it's not an option)

[goldman60]

On a basic dumb switch adding another cable wont do anything.  Fancier managed switches often support bandwidth aggregation but honestly your best bet is just to buy a cheap gigabit switch if you're worried.

[Biohazard777]

Depends on the switches used:

 

• If your unmanaged switches lack Spanning Tree Protocol (STP), adding a second cable between them creates a bridging loop. This saturates the network, rendering it unusable until the extra cable is removed.
   
• With STP-enabled unmanaged switches, only one of the switch-to-switch links is active.
   
• Manageable switches allow port aggregation/trunking for a speed boost slightly below the combined speed of the aggregated ports, accounting for some aggregation overhead.

[LAwLz]

It depends on which switch you got and how it is configured, but since you are here asking I am 99% sure the answer is "no, don't do it. It's a very bad idea".

 

With a switch that supports bundling ports, it is possible to use multiple links to increase throughput. But this requires higher-end switches, and usually special configuration.

 

With some switches, those that run Spanning Tree Protocol (STP), the switch will detect what's called a "loop", and shut down one of the ports to prevent bad things from happening to your network. You won't get any more speed, but it will prevent your network from being overloaded and going down.

 

In a worst-case scenario (which is very likely in your scenario), the switches you plug things into do not run STP and as a result, you will create a "network loop". If a loop happens in your network, your network will most likely become slower and slower until it no longer works at all, and then it will be fine again after rebooting your devices.

Basically, whenever a broadcast packet arrives at one of the switches, it will not know which port to use and as a result send the packet over both connections. This means a single packet is now two packets, and both of these packets will forever bounce back and fourth between these two switches. As more broadcast packets are sent, more and more will be duplicated and stuck in the look of being sent from Switch 1 to switch 2, then back to switch 1 again, until your entire network dies from being overloaded.