A Bridge/Switch is a network device that typically operates at the Data Link layer (Layer 2) of the OSI model. A bridge or switch performs the its job by examining the Data Link Layer (Layer 2) data packet (Ethernet Frame) and forwarding the packet to other devices based on Layer 2 addresses (MAC Addresses). Both switches and bridges function using Data Link Layer (Layer 2) addressing system, also known as MAC addresses.
Each port of a network switch is in a separate collision domain and therefore Switches are used to divide a big collision domain into multiple smaller collision domains.
Bridge has only few ports and connect only a few collision domains, or Hosts. A Bridge has comparatively less ports than a Switch. A Switch has usually 24 ports or 48 ports. Brides and Switches are considered to operate at the Data Link Layer (Layer 2) of the OSI model.
Following picture shows a 24 port, 10/100, Cisco 2950 Catalist Switch.
Following image shows a 24 port, 10/100, Cisco 2960 Switch
Difference between Network Switches and Bridges
Network Switches and Bridges are both Layer 2 devices. They operate at the Data Link Layer (Layer 2) of the OSI Reference Model. Network Switches and Bridges have many similarities and similar function. But Switches are considered as superior devices than bridges.
Following are the major differences between Network Switchs and Bridges.
• Packet forwarding in Bridges are performed using software. Packet forwarding in Switches are performed using ASICs (Application Specific Integrated Circuits).
• Switches operate comparatively higher speeds that Bridges.
• Method of switching of a Bridge is store and forward. Method of switching of a Switch can be store and forward, cut-through or fragment-free.
• Normally a Switch has more ports than a Bridge.
• Bridges can operate only in half duplex mode, but a Switch can operate both in half duplex or full duplex mode.
• Both Bridge and Switch has one collision domain per port, but switches have one broadcast domain per VLAN.
• Switchs support full-duplex Local Area Network (LAN) communication.