Switches break up collision domains and routers break up broadcast domains.
Explanation:
Collision domain depicts the part within a network where a collision can happen.
Collision occurs when two hosts transmit data packet at the same time within a network. Theses packets collide and the hosts have to resend the data after some time.
Too many collisions can result in slow traffic speed and can effect network performance.
So switches break up collision domains between the devices on a network and each port in a switch depicts a collision domain. This reduces the chance of packet collisions between the devices or hosts.
When data is to be sent to a host, the switch keeps that data frame and waits for availability of the destination host before sending the data frame.
Moreover full duplex switch mode there is not chance of collision as the transmitting path on one host is the receiving path on other host.
Broadcast domain contains all the hosts that can reach each other at the Data Link layer via broadcast.
Routers break up broadcast domains as routers contain separate broadcast domains for each interface.
Routers do not forward broadcasts from one broadcast domain to other and drop the packet when they detect a broadcast address.
