Comparison between routers and other computers

Similar to other computers, a vro also has memory, operating systems, configurations, and operating systems in the Cisco router, is called Internetwork Operating System or I o s, which is copyrighted by C I s c o ). Similar to other computers, a vro also has a boot process for loading boot programs from r o m, and for the computer to load its operating system and configurations into memory.
Vrouters are different from other computers in terms of user interface and memory configuration.
1. vro memory type

In typical d o s and u n I X 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 describes the usage of various memory in a vro.
Table 1-1 vro memory details

(1) ROM
Read-only memory r o m) contains an I O S copy used by the router. The r o m chip of the 7 0 0 0 series router is located on the vro processor board, and the 4 0 0 0 r o m chip is located on the motherboard. In the 7 0 0 0 and 4 0 0 0, the r o m chip can be upgraded to the new I O S. In the 2 5 0 0 router and 1 0 0 0 0 Series l a n extender, the r o m chip cannot be upgraded and only contains one operating system with very limited functions, only the routing selection function is available. In vrouters of the 2 5 0 0 series, I O S is in flash memory.
When running a Cisco IOS version earlier than version 11, if you connect a terminal to the Console Port during boot, you will see 2 5 0 0 series defects. After rom ios checks the configuration file, most commands cannot be identified. This will cause many errors on the screen, which is normal. When I O S in flash memory is loaded, error messages are usually not displayed.
(2) RAM
Random Access Memory r a m) is divided into shared memory and primary memory by I O S. Primary storage is used to store router configurations and I O S data structures related to routing protocols. For I p, the primary storage is used to maintain the route table and a r p table, etc. For I P X, the terms used to maintain S A P and other tables will be explained later ).
The shared memory is used to cache packets waiting for processing. This type of memory is only used by vrouters of the 4 0 0 0 and 2 5 0 0 series. In a vro 7 0 0, there is an exchange processor used to control the grouped stream through the vro.
(3) Flash Memory)
The flash memory stores the current I O S version running on the vro. R o m content cannot be rewritten, while flash memory can be erased. New I O S versions can be written to flash memory.
(4) NVRAM
Non-volatile r a MNonvolatile RAM, NVRAM) after power loss, its content will not be lost. Vro configuration information is stored in n v r a m.
2. Boot Router
The guiding process of the router is similar to that of the p c host. The process is as follows:
1) load the boot program from r o m.
2) load the OS from flash memory to IOS and connect to the network operating system ).
3) search for and load the configuration file in n v r a m or in the pre-specified network server. If the configuration file does not exist, the vro enters the setting mode.