I am trying to get a better understanding of collision domains. I understand that if I have a switch with 3 PC's plugged into the switch I have 3 collision domains. What happens if I have another switch plugged into a regular port from the switch and also a router plugged into the switch? Do I then have 5 collision domains or do I still have just the 3? One additional for the other switch and one for the router or do they not count?