Chapter 6 began with a look at the external features of a Cisco 2500 series router. This included an overview of each port, including its numbering, physical connectors, and characteristics. An overview of the router’s Ethernet port provided insight into AUI connections, transceivers, and their purpose.
A closer look a router’s serial ports included an explanation […]

Before we get into the configuration of a Cisco router in Chapter 7, we should first understand a little more about the Cisco IOS. This is an area that many people find confusing, especially when just starting out. Between the various IOS versions and release codes, it’s easy to understand why.
Note: You are not explicitly […]

Non-Volatile Random Access Memory (NVRAM) is used as the storage location for the router’s startup configuration file. After the router loads its IOS image, the settings found in the startup configuration are applied. When changes are made to a router’s running configuration, they should always be saved to the startup configuration (stored in NVRAM) or […]

In older Cisco router models, Read-Only Memory (ROM) chips were used to store the IOS software. In newer models, this is no longer the case. As mentioned previously, the IOS image is now stored in Flash memory (it can also be stored on a TFTP server, as I’ll discuss in the next chapter). ROM is […]

Random Access Memory (RAM) represents the non-permanent or volatile working area of memory on a Cisco router. When the router is powered down, the contents of RAM are lost.
By default, RAM is broken up into two main areas – Main Processor Memory, and Shared I/O Memory. Main Processor Memory is where the routing table, ARP […]

Flash memory is implemented on a Cisco 2500 using two Single Inline Memory Module (SIMM) slots that hold erasable programmable read-only memory (EPROM). Flash memory is used to store and run the Cisco IOS software. When a system is powered down, the contents of Flash memory are not lost. However, its contents can be upgraded […]

The internal components of the router are where the real magic takes place. Think of a Cisco router are being really no more than a specialized computer running a custom operating system. In this case, it is a computer optimized to provide routing and related functions. Instead of relying on a hard disk for storage, […]

On any given Cisco router, the LED lights provide quick insight into whether the system or ports are functioning correctly. On a Cisco 2500 series router, each port (with the exception of the console and auxiliary ports) has an associated LED that indicates port activity, in a fashion similar to what you might expect to […]

The purpose of the auxiliary port is for connecting to an external modem. Once configured, this modem can be used as a backup demand-dial connection to another location, or as a way to dial in to the router for troubleshooting purposes should regular connectivity fail. Unlike the console port, the auxiliary port supports hardware flow […]

In order to connect to the console port, you’re going to require what Cisco calls a rollover cable. While these are usually provided with a router, they are also exceptionally simple to create. All that you require is a reasonable length of twisted pair cabling, some RJ-45 connectors, and the ability to remember what rollover […]