This document discusses the different types of memory used in routers and how they function. RAM is used to run the IOS and hold routing tables and packet buffers. ROM contains the bootstrap and POST programs to start the router. NVRAM stores the configuration register and configuration files. Flash stores the IOS by default. The configuration register controls how the router boots. CDP is used to synchronize time and collect information about neighboring devices.

1.  Bootstrap it is used to bring up during initialization. It boots the router up
and then loads the IOS.
POST it is used to check the basic functionality of the router hardware and
determines which interfaces are present.
Rom monitor it is used for manufacturing ,testing and troubleshooting , as well as
running a mini-ios when the ios in flash fails to load.
RAM used to hold packet buffers, routing tables and softwares that allow
router to work. Running-config is used to stored in RAM and most of the router
expand the IOS from flash into RAM upon boot
 ROM used to start and maintain the router. Holds the POST and the
bootstrap program as well as the mini – IOS.
NVRAM used to hold the router and switch configuration. NVRAM is not
erased when the router or switch is reloaded . Does not store an IOS. The
configuration register is stored in NVRAM.
Flash store the cisco IOS by default . Flash memory is not erased when
router is reloaded. It is EEPROM created by Intel.
Configuration register used to control how the router boots up.

2. Default order of an IOS loading from a cisco
device begins with flash, then TFTP SERVER,
and finally , ROM.

3. Show running config
Sh start
Copy running-config startup-config
Copy running-config ?
Copy running-config tftp
Ip of tftp
Enter
copy tftp running-config
Ip
File name
Erase startup-config

4. TIME TO ALL YOUR NETWORK DEVICES.
NTP synchronize clocks of computer systems over packet switched data
network.
Time can then be synchronized through the network to keep all routers,
switches, servers, etc. receiving the same time information.

5. It is the proprietary protocol designed by cisco to help administrators collect
information about locally attached devices.
Show cdp command gives you information about two CDP global parameters that can
be configured on cisco devices:
CDP timers delimits how often CDP packets are transmitted out all active
interfaces.
CDP holdtime delimits the amount of time that the device will hold packets
received from neighbor devices.
Sh cdp
Cdp ?
Cdp timer ?
No cdp run
Cdp run
Sh cdp neighbors