3.1 Switching Technologies

Key Concepts

• Layer 2 Switching
• Layer 3 Switching
• Virtual Switching

Layer 2 Switching

Layer 2 Switching operates at the Data Link layer (Layer 2) of the OSI model. It uses MAC addresses to forward data packets between devices on the same network segment. Key features include:

• MAC Address Learning: Switches learn the MAC addresses of devices connected to their ports and store this information in a MAC address table.
• Forwarding/Filtering: Based on the MAC address table, switches forward packets only to the specific port where the destination device is located, reducing unnecessary traffic.
• Broadcast/Multicast Handling: Switches handle broadcast and multicast packets by forwarding them to all ports except the incoming port.

Example: Imagine a switch as a mail sorter in a post office. It knows the addresses of all the mailboxes (MAC addresses) and delivers letters (data packets) directly to the correct mailbox, avoiding unnecessary distribution.

Layer 3 Switching

Layer 3 Switching operates at the Network layer (Layer 3) of the OSI model. It uses IP addresses to route data packets between different network segments. Key features include:

• Routing: Layer 3 switches can route packets between different subnets, similar to routers, but with the high-speed performance of switches.
• IP Address Learning: These switches maintain routing tables that map IP addresses to specific ports, allowing them to make forwarding decisions based on IP addresses.
• Quality of Service (QoS): Layer 3 switches can prioritize certain types of traffic based on IP addresses, ensuring critical applications receive the necessary bandwidth.

Example: Think of a Layer 3 switch as a sophisticated mail sorter that not only knows the addresses of mailboxes but also understands city and state (IP addresses) to deliver mail between different neighborhoods efficiently.

Virtual Switching

Virtual Switching involves the use of virtual switches within virtualized environments, such as hypervisors. Key features include:

• Virtual Network Interface Cards (vNICs): Virtual switches connect virtual machines (VMs) to the physical network through virtual network interface cards.
• Network Isolation: Virtual switches can create isolated virtual networks, allowing different VMs to communicate without interfering with each other.
• Dynamic Configuration: Virtual switches can be dynamically configured and reconfigured as VMs are created, moved, or deleted, providing flexibility and scalability.

Example: Consider a virtual switch as a digital mail sorter within a large office building. It manages the flow of mail (data packets) between different departments (VMs) while ensuring that each department's mail stays within its own area, maintaining privacy and efficiency.