Basic knowledge of network and router Fault Diagnosis (1)

Network diagnosis is a comprehensive technology that involves all aspects of network technology. To facilitate the following discussion, we will first briefly review the basic concepts of networks and routers.

A computer network is a system composed of computers and communication facilities. It connects geographically dispersed computers by various communication means, systems that communicate with each other and share software, hardware, data, and other resources. Computer Networks are generally divided into LAN and WAN according to their computer distribution. Lan covers a small geographical range, generally ranging from several meters to dozens of kilometers. The wide area network covers a large geographical range, such as campuses, cities, and even the world. The development of computer networks leads to various forms of connections between networks. Unified protocols are used to interconnect different networks, making the interconnected networks easy to expand. The Internet is the network connecting networks in this way. The Internet uses TCP/IP protocol as the communication protocol to connect computer networks in the world and become the world's largest and most popular international network.

In order to complete the communication between computers, the interconnection functions of each computer are divided into clearly defined layers, and protocols for Process Communication at the same layer and interfaces and services between adjacent layers are defined, the protocols for communication between these layers and processes at the same layer and interfaces between adjacent layers are collectively referred to as the network architecture. The Open System Interconnection Reference Model OSI proposed by ISO is the core of the modern computer network technology system. This model divides network functions into seven layers: physical layer, data link layer, network layer, transmission layer, Session Layer, presentation layer, and application layer.

TCP/IP is a set of network protocols. TCP/IP originated from ARPANET, which has become a standard communication protocol used by the Internet. TCP/IP enables computers using different operating systems to exchange data in an orderly manner.

A vro is a network device used for network connection and route selection tasks. The router works at the network layer, forwards packets, and has the filtering function. A vro can connect two networks using different technologies and establish a network connection between multiple types of networks, such as the LAN or WAN. It transmits the information at the network layer of the layer-7 model from the network layer to the network layer of the other network based on the fastest and most direct routing principle to achieve the best route selection. At the same time, high-speed internal BUS is used internally to connect interfaces suitable for various network protocols. It also provides multiple network management functions to monitor some network devices connected to routers and their configuration and running status.

CISCO routers are the most commonly used routers in network construction. They come in a variety of grades and series. Currently, they are commonly used in the 2500 series. This article takes the 2500 series as an example. Vrouters of the 2500 series are fixed-interface multi-protocol routers that support all cisco ios functions. According to the specific Protocol environment, there are four types: Fixed-configuration vro2501 2507), router 2514 with hub port), router 2511 with touch block) and access server ). They are simple in structure, easy to operate, easy to configure and manage. They are a routing device used for small-scale LAN and WAN network layer relay.