In your CCNA certification exams you have to tackle many technical questions regarding the Cisco products and services such as questions regarding the operation and configuration of a basic Cisco IOS router. Cisco IOS (Internetwork Operating System) is a standard software operating system that runs on most of the Cisco networking gadgets such as switches and routers. There are almost all size of routers found in a networking setup depending upon the size and data traffic between networks. The operation and configuration of a Cisco IOS router requires the in-depth understanding of the Cisco IOS Configuration Commands by making use of the Command Line Interface (CLI) for the configuration and troubleshooting of the Cisco device.
How to Connect and Configure the Cisco Router?
There are two ways to connect a Cisco router, directly or remotely. Generally the direct connection of the router is advised when the router is new and not configured yet. This type of router connection is done with a Cisco console cable via the CONSOLE port. While the remote connection of the Cisco router is done by dialing a modem connected to an AXU Port. These methods of the router connection are known as "out-of-band" connection methods. After the next configuration of the Cisco router the next step is to assign IP addresses to their interfaces. Once you do so then you can connect router with a network by using an in-bond connection method using Telnet or SSH protocols.
Router Configuration Modes
Once your Cisco router is connected using a console cable and console port, after that you are given a Command Line Interface to type and execute router configuration commands. Once you type the configuration command, hit enter key and your configuration command becomes active on your Cisco device. For instance, if you type the command "Shut Down" on your router interface it automatically halts the interface.
Now the question is what method should be used to access or configure a Cisco Router? These days there are two commonly used Router Configuration Modes;
User EXEC Mode: in this mode only few monitoring commands can be accessed while no configuration is allowed using this mode. The command to use this mode is "router>"
Privileged EXEC Mode: this mode allows access to all the commands related to the configuration and management of the Cisco devices. This mode allows full access to the devices and its access can be restricted using a password. This method is also known as the "enable mode" as you get access to it using an enable command. The command to access this mode is "router#". If you have access to a privileged EXEC mode only then you can configure the device by using "configure terminal".
Router Memory Types
There are four memory types for a Cisco router:
1. ROM: In this part of the Cisco router memory POST script of the router is based. The POST software (Power on Self Test) performs the initial start up hardware checking for the router A mini-IOS is also located in ROM to recover lost passwords.
2. RAM: this type of memory holds the running configuration is located. IOS software is loaded into RAM once the device is booted. Most of the routing tables and network parameters during operation also reside in RAM. The configuration of the router is in fact the changing of the running-configuration that mentioned above RAM holds.
3. NVRAM: NVRAM stores the running configuration from RAM that we save using the command "write" and these ruining configurations become the initial startup-configuration. Router once rebooted loads these start up configuration from NVRAM. After rebooting the router, the startup-configuration is loaded from the NVRAM.
4. Flash: Flash memory type of a router acts like the hard disk of a PC. The image files for the IOS software any backup configurations that you save occasionally also reside in Flash.
When you execute the "show running-configuration" command on your router interface it shows you the current running configuration in the RAM memory part. And when you execute the "show startup-configuration" you send a command to the router to show you the stored configuration in the NVRAM.
