The similarities and differences between Cisco routers and computers

Now let's take a look at the similarities and differences between Cisco routers and other computers on the Interconnect Network. Similar to other computers, a vro also has memory, operating system, configuration, and user interface (the operating system in a Cisco router is called InternetworkOperatingSystem or IOS, all rights reserved by Cisco ). Similar to other computers, a router also has a boot process for loading boot programs from the ROM, and for the computer to load its operating system and configurations into the memory.

Vrouters are different from other computers in terms of user interface and memory configuration.

1. vro memory type

In Typical DOS and UNIX systems, the storage is physically divided into multiple storage bodies, each of which is assigned different functions by the software. A vro also has multiple storage bodies, each of which is used for different functions. The functions of these storage bodies vary with vrouters.

Table 1-1 lists the usage of various storage devices in routers.

(1) ROM

Read-only memory (ROM) contains an IOS copy used by the router. The ROM chip of the 7000 series router is located on the vro processor board, and the 4000 ROM chip is located on the motherboard. In versions 7000 and 4000, the ROM chip can be upgraded to the new IOS version. In the 2500 router and 1000 Series LAN extenders, the ROM chip cannot be upgraded and only contains one operating system with limited functions. Only the routing function is available. In vrouters of the 2500 series, IOS is in flash memory.

When running CiscoIOS earlier than version 11, if you connect a terminal to the Console port during the boot, you will see the 2500 series defects. After ROMIOS checks the configuration file, most commands cannot be identified. This will cause many errors on the screen, which is normal. When IOS in flash memory is loaded, there is usually no error message displayed.

(2) RAM

Random Access Memory (RAM) is divided into shared memory and primary memory by IOS. Primary storage is used to store router configurations and IOS data structures related to routing protocols. For IP addresses, primary storages are used to maintain route tables and ARP tables. For IPX, primary storages are used to maintain SAP and other tables. The shared memory is used to cache packets waiting for processing. This type of memory is only used by vrouters 4000 and 2500. In vrouters 7000, there is an exchange processor used to control the grouped stream through the vro.

(3) Flash (Flash)

Flash memory stores the current IOS version running on the vro. The content of the ROM cannot be rewritten, while the flash memory can be erased. The new IOS version can be written to the flash memory.

(4) NVRAM

NonvolatileRAM (NVRAM) is not lost after power loss. The vro configuration information is stored in NVRAM.

2. Boot Router

The guiding process of a vro is similar to that of a PC. The process is as follows:

1) load the boot program from the ROM.

2) load from flash memory to the Operating System (IOS, interconnected network operating system ).

3) Find and load the configuration file in NVRAM or the configuration file in the pre-specified network server. If the configuration file does not exist, the vro enters the setting mode.

1. What is the difference between a computer and a router?
2. Comparison between routers and other computers