Layer 2 Forwarding
Layer 2 forwarding refers to the process of forwarding data packets at the data link layer of the OSI model. This layer is responsible for transmitting data between adjacent network nodes, such as switches or bridges, over a physical medium such as an Ethernet cable.
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| Fig 1: Layer 2 Forwarding |
In order to forward a packet, a Layer 2 switch needs to perform two basic operations: MAC address learning and MAC address forwarding.
MAC address learning is the process by which the switch learns the MAC addresses of devices connected to its ports. When a switch receives a packet on a port, it examines the source MAC address in the packet header and associates it with the port on which the packet was received. The switch then updates its MAC address table, which maps MAC addresses to switch ports.
MAC address forwarding is the process by which the switch forwards packets based on their destination MAC address. When a switch receives a packet, it looks up the destination MAC address in its MAC address table. If the destination MAC address is not found, the switch floods the packet out all its ports except the one on which the packet was received. This is done in order to reach the destination device, which may be connected to one of the other ports.
If the destination MAC address is found in the MAC address table, the switch forwards the packet out the corresponding port. This process is repeated for every packet received by the switch.
Layer 2 forwarding is essential for building local area networks (LANs) where multiple devices need to communicate with each other. By using switches to forward packets based on MAC addresses, network administrators can create a more efficient and reliable network than if they were to use hubs or routers.
Summary
In summary, Layer 2 forwarding is the process by which a switch forwards data packets based on their MAC addresses. It involves two basic operations: MAC address learning and MAC address forwarding. By using Layer 2 forwarding, network administrators can create efficient and reliable LANs.
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