A router is a network device that is used to transfer packets between different networks. It has multiple network interfaces to connect to different networks and transmit packets from one network to another based on the destination address.
How a router works
A router determines how to transmit packets from a source address to a destination address by maintaining a routing table. The routing table contains a mapping relationship between network addresses and next-hop addresses.
When a router receives a packet, it looks up the routing table, determines which interface the packet should be sent to, and then forwards it to the appropriate interface.
Routers exchange routing information with each other through routing protocols to update each other’s routing tables. Common routing protocols include RIP, OSPF, BGP, and so on.
Memory Tip: The working principle of router can be remembered only three key words: routing table management, packet forwarding, routing protocols.
Functions of Router
Connecting Networks: Routers can connect different networks, such as LANs and WANs, to realize communication between different networks.
Network Address Translation (NAT): Routers can implement the NAT function to map IP addresses within a private network to public IP addresses, enabling communication between internal hosts and external networks.
Security features: Routers often include firewall features that filter network traffic and protect the internal network from external attacks.
Load balancing: Some advanced routers support load balancing function, which can automatically adjust the transmission path of packets according to network traffic to improve network performance.
Types of Routers
Home Router: Used for home networking, it usually contains both wired and wireless interfaces to support the connection and sharing of home networks.
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Enterprise Router: Used for corporate networks, usually with more robust performance and security features to support large-scale network deployments.
Core Router: Used in the core nodes of the Internet, it undertakes the task of transmitting and routing and forwarding Internet packets, with extremely high performance and reliability requirements.