the internal structure of 4g industrial routers

In modern internet architecture, routers serve as the pivotal connection points between different networks, playing a crucial role. Whether it’s a simple home network or a complex enterprise network architecture, routers are an indispensable part.

However, many network engineers might not have a clear understanding of their internal structure, but gaining more knowledge is always beneficial.

It’s important to know that routers primarily utilize four types of memory:

Read-Only Memory (ROM)

Flash Memory

Random Access Memory (RAM)

Non-Volatile RAM (NVRAM)

Among all types of memory, RAM is the only one that loses its content when the router is powered off or restarted.

1 What is a Router?

A router is a network device used to forward data packets between networks.

It analyzes the destination address of data packets and forwards them along the optimal path based on predefined routing strategies, enabling communication between different networks.

01 Router Functions
Packet Forwarding: Identifies and forwards data packets to the correct destination.

Addressing: Uses IP addresses to identify the source and destination of data packets.

Path Selection: Chooses the best path based on network topology and policies.

Network Isolation: Prevents broadcast storms and reduces network congestion.

Network Security: Implements Access Control Lists (ACLs) and other security measures.

02 Router Classification

the internal structure of 4g industrial routers

Edge Routers: Located at the edge of networks, connecting different networks.

Core Routers: Positioned at the center of networks, responsible for high-speed data exchange.

Access Routers: Provide access services for users.

2 Router Hardware Structure

the internal structure of 4g industrial routers

01 Processor
The processor in a router is one of its core components, responsible for running the operating system and executing various network protocols. High-performance routers typically use multi-core processors to handle high-load packet processing tasks.

02 ROM (Read-Only Memory)
ROM stores the router’s boot program, which is the first program loaded when the router starts up. It initializes the hardware and loads the operating system.

03 RAM (Random Access Memory)
RAM is the primary working memory of the router, used to store routing tables, ARP caches, temporary data, and other runtime information. Two notable things are the IOS system table and buffers. IOS uses RAM to meet all its regular storage needs.

The main function of NVRAM is to save the configuration data that IOS reads when the router starts. This configuration is called the “startup configuration.”

04 Flash Memory
Flash memory is used to store the router’s operating system image, configuration files, firmware updates, and other static data. It is non-volatile, retaining data even when powered off. If a router is equipped with flash memory, it is the default location for booting the IOS software.

As long as the flash memory capacity is sufficient, multiple IOS images can be saved, providing multiple boot options. Flash memory can either be built into the motherboard’s SIMM or made into a PCMCIA card.

05 Interfaces
Routers have various types of interfaces for connecting different network devices. Common interfaces include Ethernet ports, fiber optic ports, etc. Some high-end routers also come with USB ports for peripheral expansion.

In routers using IOS, each interface has its own name and number. A full interface name consists of its type identifier and at least one number. The numbering starts from zero.

For routers with fixed interfaces or modular interfaces that can only be changed when the router is powered off, the full interface name contains only one number, sequentially numbered according to their physical order on the router.

For example, Ethernet0 is the name of the first Ethernet interface, and Serial2 is the name of the third serial interface.

If the router supports “hot insertion and removal” or has the ability to dynamically change physical interface configurations (hot-swappable cards) without powering off the router, the full interface name should contain at least two numbers separated by a forward slash (/).

The first number represents the slot number where the interface processor card will be installed, and the second number represents the port number of the interface processor.

06 Console Port
The console port is a dedicated port on the router used for local management. Administrators can connect to this port via a serial line and use the command-line interface for configuration and troubleshooting.

The type of physical connection to the console port depends on the router model. Some routers use a DB25 female connector (DB25F), while others use an RJ45 connector.

Typically, smaller routers use RJ45 console connectors, while larger routers use DB25 console connectors.

07 Auxiliary Port
The auxiliary port is usually used for remote management of the router. It allows for establishing a remote connection via a modem, enabling management when network access to the router is unavailable.

the internal structure of 4g industrial routers

3 Software Architecture

01 Operating System
Most routers run proprietary embedded operating systems, such as Cisco IOS, Junos OS, etc. These operating systems contain the software stack required to implement routing functions.

02 Software Components
In addition to the operating system, routers run a series of software components such as protocol stacks, applications, and services. These components work together to accomplish complex network tasks.

03 Protocol Stack
TCP/IP Protocol Stack: Responsible for encapsulating and decapsulating data packets.

Routing Protocols: Such as RIP, OSPF, BGP, etc., used for learning and updating routing tables.

04 Applications and Services
Web Server: Provides web interface configuration options.

SSH Service: Securely manages the router remotely.

SNMP Agent: Monitors and manages the router’s status.

05 Software Updates and Maintenance
The router’s operating system and supported services often need updates to fix security vulnerabilities and add new features. These updates are usually installed via flash memory.