Cisco routers have four basic types of memory: RAM/DRAM, NVRAM, ROM, and Flash (EPROM) memory.
|RAM/DRAM||Active program and operating system instructions, the running configuration file, routing tables|
|NVRAM||Startup configuration file|
|ROM||POST, bootstrap, and startup/power-up utilities (usually limited version of), Cisco IOS|
For the exam, remember that the router's RAM is volatile DRAM that holds the working data and files of the router, and when the power is turned off, the contents of the RAM are lost.
Where DRAM is volatile and must have a power source to hold its contents, nonvolatile RAM (NVRAM) can hold its contents when the main power source is lost. You may even know this type of memory as static RAM (SRAM), but on the CCNA exam, remember it as NVRAM. The Cisco router uses NVRAM to store its startup configuration file.
There's another type of memory, called ROM (Read-Only Memory), that's even more reliable than NVRAM. Like NVRAM, ROM does not lose its contents when the power is turned off. On the Cisco router, ROM contains the program instructions for the power-on self-test (POST) diagnostics, the bootstrap program, which is the startup program for the router, and the router's operating system.
Cisco routers contain two copies of the IOS, a stripped won version that is stored in ROM and the full up-to-date version stored in Flash. The IOS version in Flash memory is the one you should focus on for the exam.
The Cisco Discovery Protocol (CDP) is a proprietary Cisco protocol that allows you to get information about directly connected CIsco router, bridges, and switches.
Stuff to memorize about CDP
The two Exec modes in the user interface are User Exec and Enable Exec (a.k.a. Privileged) modes.Setup Mode
Another way to restart the router is to issue the reload command.
Like the setup mode, you can enter the configuration mode by using a command, in this case config. To move into what is called global configuration mode, enter the following config command at the Enable Exec prompt (the one with the # symbol):
The parameter terminal or its abbreviation t is absolutely necessary.
Enhanced Editing Keyboard Commands
|Ctrl+A||Move to the beginning of the current line|
|Ctrl+E||Move to the end of the current line|
|Ctrl+B (or left-arrow key)||Move back one character|
|Ctrl+F (or right-arrow key)||Move forward on character|
|Ctrl+N (or down-arrow key)||Recall most recent command|
|Ctrl+P (or up-arrow key)||Recall previous command|
|Esc+B||Move back to beginning of previous word (or beginning of current word).|
|Esc+F||Move forward one word|
|Tab||Complete the current word (shortcut command)|
Other configuration commands used in editing the comand history are:
Naming Your Router