Bridge, Gateway, and Router

A router can perform the functionality of both a bridge and a gateway, but not all at once in the same mode, and not in the full capacity of dedicated devices. Let explain with comparison table 

Bridge

A bridge is a networking device that connects and filters traffic between similar network segments operating on the same protocol, such as Ethernet. It works at the Data Link Layer (Layer 2) and uses MAC addresses to forward data, helping to reduce traffic and collisions within a LAN.

Criteria Bridge Capability Explanation
Connects similar networks ✅ Yes A bridge connects similar networks (e.g., two Ethernet LAN segments) that use the same protocol.
Connects different networks ❌ No A bridge cannot connect different types of networks. It only works with similar networks using the same protocol.
Uses similar protocols ✅ Yes A bridge operates with networks that use the same protocol (e.g., Ethernet to Ethernet).
Uses different protocols ❌ No A bridge does not handle protocol conversion. If the networks use different protocols, a gateway is required.

Gateway

A gateway is a network device that connects entirely different networks that may use different communication protocols. It performs protocol conversion and often operates at multiple OSI layers, including the Application and Transport layers. Gateways are essential for enabling communication between incompatible systems, such as a private LAN and a public phone network or between IP and VoIP systems.

Criteria Gateway Capability Explanation
Connects similar networks ✅ Yes A gateway can connect similar networks if the same protocol is used, but its main role is to connect dissimilar networks.
Connects different networks ✅ Yes A gateway is designed to connect different networks using different protocols (e.g., IP to VoIP, LAN to PSTN).
Uses similar protocols ✅ Yes (sometimes) A gateway can work with similar protocols (e.g., IP networks to the Internet) but usually involves protocol translation when necessary.
Uses different protocols ✅ Yes A gateway is specifically designed to handle protocol conversion and can translate between different protocols (e.g., IP to VoIP, or LAN to Email).

Router

A router is a device that connects different IP-based networks and directs data packets between them using IP addresses. Operating at the Network Layer (Layer 3), it ensures proper routing of traffic between subnets or between a local network and the Internet, even if the underlying technology is the same.

Criteria Router Capability Explanation
Connects similar networks ✅ Yes A router can connect two networks that use the same technology (e.g., Ethernet LANs), but they must be logically separated (i.e., in different IP subnets).
Connects different networks ✅ Yes Routers are primarily used to connect different networks, such as a LAN to the Internet (WAN), or two branch offices.
Uses similar protocols ✅ Yes (usually IP-based) Routers work with same protocol families, typically IP (IPv4/IPv6). They do not translate between protocols.
Uses different protocols ❌ No (not by default) Routers do not handle protocol conversion. If two networks use different protocols (e.g., IP and AppleTalk, or IP and VoIP), a gateway is needed, not a router.

Key Differences Between Bridge, Router, and Gateway

Aspect Bridge Router Gateway
Main Function Connects and filters traffic between similar network segments Routes data between different networks Translates communication between different protocols/networks
OSI Layer Data Link Layer (Layer 2) Network Layer (Layer 3) All layers (primarily Application, Transport)
Network Type Similar networks (same type & protocol) Different IP-based networks (same protocol family) Different networks (often with different protocols)
Protocol Handling Same protocol only (e.g., Ethernet to Ethernet) Same protocol (e.g., IP to IP) Different protocols (e.g., IP to VoIP, or LAN to Internet)
Traffic Decision Basis MAC address IP address Protocol and content translation
Use Case Example Segmenting a LAN to reduce congestion Connecting a home/office network to the Internet Connecting dissimilar networks (e.g., LAN to PSTN)