Switch

• Work in Layer2.

Switch is fast than Bridge.

• Because

MAC Learning.

CAM Content-addressable memory table/MAC address table * Get source mac by sniffer ports and save in DB.

• Include from which port.

How switch send frame ? 1. Check CAM and send if match. 2. Send to all ports exclude source port. (Flooding) 3. CAM will clean entry after a counter

Send mode of switch

• Store and Forward

  • Get frame totally include source MAC and destination MAC.

  • Check by CRC (Cyclic Redundancy Check)

  • If CRC fail, then drop frame.

  • Cost much time.

• Cut Through

  • Forward only by source MAC.

  • Fast

• Adaptive Cut-Though

• Fragment-Free

Intelligent Forwarding

• Swtich has all devoce MACs in the network

Normal Topology of switch

Switch could be a backup path when switch is shutdown.

ISSUE Broadcast Storm

• Made by broadcast packet.

• Broadcast packet

  • DHCP req

  • ARP req

Multiple Frame Copies

MAC Address Table Instability

SOLUTION

STP (Spanning Tree Protocol)