The two methods to connect a PC to a network device to perform configuration and monitoring tasks are in-band and out-of-band management.
In-Band Management
In-band management is used to monitor and make configuration changes to a network device over a network connection. For a computer to connect to the device and perform in-band management tasks, at least one network interface on the device must be connected to the network and have an IP address configured on it. Telnet, SSH, HTTP, or HTTPS can be used to access a Cisco device for in-band management, monitor the network device, or make configuration changes. Telnet and HTTP send all data, including passwords, in cleartext and therefore should be used only in a lab environment.
Out-of-Band Management
Out-of-band management requires a computer to be directly connected to the console port of the network device that is being configured. This type of connection does not require the local network connections on the device to be active. Technicians use out-of-band management to initially configure a network device, because until properly configured, the device cannot participate in the network. Out-of-band management is also useful when network connectivity is not functioning correctly, and the device cannot be reached over the network. Performing out-of-band management tasks requires a terminal emulation client installed on the PC.
IOS Startup Files (17.2.4)
As shown in Figure 17-11, a Cisco device loads the following two files into RAM when it is booted:
Figure 17-11 Memory Location of IOS and Startup Configuration
- IOS image file—The IOS facilitates the basic operation of the device‛s hardware components. The IOS image file is stored in flash memory.
- Startup configuration file—The startup configuration file contains commands that are used to initially configure a router and switch and create the running configuration file stored in RAM. The startup configuration file is stored in NVRAM. All configuration changes are stored in the running configuration file and are implemented immediately by the IOS.
The running configuration file is modified when the network administrator performs device configuration. When changes are made to the running-config file, it should be saved to NVRAM as the startup configuration file in case the router is restarted or loses power.
Video—Establish a Console Connection (17.2.5)
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Cisco Routers (17.3)
A router is a computer with specialized hardware and a network operating system. A computer, such as a PC running Linux, could even be configured as a router for a small network. Cisco routers have specialized hardware and software designed to provide the features and performance needed for enterprise and service provider networks.
Video—Cisco Router Components (17.3.1)
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Router Components (17.3.2)
Regardless of their function, size, or complexity, all router models are essentially computers. Just like computers, tablets, and smart devices, routers also require the following:
- Operating system (OS)
- Central processing unit (CPU)
- Random-access memory (RAM)
- Read-only memory (ROM)
- Nonvolatile random-access memory (NVRAM)
Like all computers, tablets, and smart devices, Cisco routers require a CPU to execute OS instructions, such as system initialization, routing functions, and switching functions.
The Cisco Internetwork Operating System (IOS) is the system software used for most Cisco devices, regardless of the size and type of the device. It is used for routers, LAN switches, small wireless access points, large routers with dozens of interfaces, and many other devices.
Router Interface Ports (17.3.3)
Although several different types and models of routers are available, every Cisco router has the same general hardware components.
Figure 17-12 shows a Cisco 4321 Integrated Services Router (ISR).
Figure 17-12 Connections on the Cisco 4321 ISR
The router includes the following connections:
- Console ports—Two console ports for the initial configuration and command-line interface (CLI) management access using a regular RJ-45 port and a USB mini-B connector.
- Two LAN interfaces—Two Gigabit Ethernet interfaces for LAN access labeled GE 0/0/0 and GE 0/0/1. The GE 0/0/0 port can be accessed through an RJ-45 connection or by using a small form-factor pluggable (SFP) attachment to provide a fiber-optic connection.
- Network interface modules (NIMs)—Two NIM expansion slots that provide modularity and flexibility by enabling the router to support different types of interface modules, including serial, digital subscriber line (DSL), switch ports, and wireless.
The Cisco 4321 ISR also has a USB port, a management interface, and an auxiliary port. The USB port can be used for file transfers. The management port can be used for remote management access when the two Gigabit Ethernet interfaces are unavailable. The auxiliary port provides legacy support for a method of connecting a dial-up modem to the router for remote access. The auxiliary port is rarely used in networks today.