A network bridge is a device or software component used in computer networks to connect two separate network segments together, allowing communication between them. It operates at the data link layer (Layer 2) of the OSI model and is responsible for forwarding data packets between different network segments.
The primary function of a network bridge is to extend the network by connecting two separate LANs (Local Area Networks) or network segments into a single logical network. It achieves this by examining the MAC (Media Access Control) addresses of incoming data packets and making forwarding decisions based on this information.
Types of network bridges
Transparent Bridge: This is the most common type of bridge. It operates at the MAC layer and is transparent to the connected networks. It learns the MAC addresses of devices on each segment and uses this information to forward packets efficiently.
Source Route Bridge: This type of bridge is less common and operates at the network layer (Layer 3). It uses source routing information provided by the sender to determine the path of packet forwarding.
Translation Bridge: Also known as a protocol bridge, this type of bridge translates network protocols between different network segments. It allows devices using different protocols to communicate with each other.
Wireless Bridge: A wireless bridge connects two separate wireless networks together, allowing them to communicate. It typically uses Wi-Fi technology to establish the connection.
The functions of a network bridge
Forwarding: The primary function of a bridge is to forward data packets between different network segments. It examines the source and destination MAC addresses of incoming packets and forwards them to the appropriate destination segment.
Address Learning: Bridges learn the MAC addresses of devices connected to each network segment by observing the source addresses of incoming packets. This learning process allows them to build a forwarding table, which is used to make forwarding decisions efficiently.
Filtering: A bridge can filter network traffic by examining the destination MAC address of each packet. It only forwards packets to the segment where the destination device is located, reducing unnecessary traffic on other segments.
Collision Domain Isolation: Bridges divide a network into separate collision domains. In a shared Ethernet network, a collision occurs when two devices transmit data simultaneously, causing data loss. By isolating collisions to individual segments, bridges can improve network performance.
Broadcast Domain Isolation: Bridges also isolate broadcast domains, preventing broadcast traffic from being forwarded to all segments. This helps reduce unnecessary network traffic and improves overall network performance.
Network Segmentation: By connecting multiple network segments, bridges allow for network segmentation. This segmentation can improve network performance, security, and manageability by dividing a large network into smaller, more manageable parts.
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