Can I use Cat6 cables on a Cat5 switch?

I will change the switch to Cat6 next week, but I need the net to work with the old switch for a few days.

What happens when you plug a Cat6 cable to a cat5 port ?

What makes Cat 5 and 6 cables different are their electrical specifications and therefore signal transmission capabilities. Category 6 cable has better specifications than 5 or 5e, enabling it to so support faster data transmission when installed with compatible devices.

However, Cat 6 cable is backward compatible with previous specifications, and it can be deployed in networks using older hardware without problems. In fact, it's typical to use newer cabling types when upgrading a physical network infrastructure, even though the hardware is still using older standards. This is how a network admin can get newer cable installed in preparation for a future time when newer hardware will be deployed.

Bottom line: You can do what you're planning and it will work just fine.