CCNA(5th class)

Router:

• It is a layer-3 device.
• Stops broadcast by default/ doesnot forward broadcast across itself.
• Internetwork communication
• Path Selection
• Each port of a router is a broadcast domain.
• One port of a router= 1 broadcast domain= 1 network

Router components:

• ROM

Stores bootstrap and basic operating system software

• RAM

Volatile in nature
Loses content when power is down
Stores  running configuration

• NVRAM

Non volatile RAM
Stores start up configuration

• Flash

Stores CISCO IOS
Can store multiple version of IOS

• Console

RS-232 protocol  is used to connect through console
Doesnot require IP for communication
Is used for initial configuration or first time configuration of Cisco device.

• Interfaces

Supports multiple interface type
E.g. Ethernet, Fast Ethernet, GigaBit Ethernet, field fibre(GBIC/ SFP), serial interface(WIC-1T, WIC-2T, NM-4A/S, etc.)

Boot process of a router

1. POST(Power On Self Test) Execute diagnostic from ROM on several hardware component
2. Execute bootstrap after POST is successful
3. Loads IOS from Flash. (if not , fall down from TFTP)
4. Looks for valid configuration in NVRAM(NVRAM-> TFTP-> Console)
5. If configuration is present, loads the configuration. If not, enters into set-up mode.

CISCO IOS mode
Hierarchial instruction each mode is to accomplish particular task
Each mode has specific set of commands,

1. User Exec mode
View only mode
Limited command
Syntax: Router >

2. Privilege Exec mode
File manipulation
Debugging and testing
Certain configuration command
Syntax: Router #

3. Global configuration mode
Entry to other specific configuration mode
Changes made in this mode affects the router globally
Syntax: Router (config) #

Interface configuration mode
Command related configure and interface
Router(config-if) #

Line configuration mode
Commands related to console and vty terminal
Router(config-line) #

Router>  --User exec mode
Router> enable
Router#--Privilege exec mode
Router# configure terminal
Router (config) # ---- Global configuration mode

Setting host name
Router (config) # hostname RTR
RTR (config) #

Setting Clock
RTR (config) # exit
RTR # clock set hh:mm:ss <Day of month> <Month of the year> <Year>

Putting IP address on interface
RTR (config) # interface f0/0
RTR (config) # description ***Connected to LAN***
RTR (config) # IP address 192.168.1.1    255.255.255.0
RTR (config) #no shut down
RTR (config) # exit

Securing console
RTR (config) # line console 0
RTR (config-line) # password console 1
RTR (config-line) # login
RTR (config-line) # logging synchronous
RTR (config-line) # exit

Securing remote access
RTR (config) # line vty 0 4
RTR (config) # password telnet1
RTR (config) # login
RTR (config) # logging synchronous
RTR (config) # exit

Securing privilege exec mode
RTR (config) # enable password laba_ccna
OR
RTR (config) # enable secret laba_ccna1

Encrypting all future and current passwords
RTR (config) # service password- encryption

Banner
RTR (config) # banner motd # Unauthorized access is prohibited #

Enabling timestamp on debug and log message
RTR (config) # service timestamp debug date time msec
RTR (config) #service timestamp log date time msec

Saving configuration
RTR # copy running-config startup
OR
RTR # copy run start
OR
RTR # write memory
Erasing the configuration
RTR # write erase
RTR # reload -> reloading the router

Verify
RTR # show running config
RTR # show startup config
RTR # show clock
RTR # show flash
RTR # show version
RTR # show IP interface brief
RTR # show interface [interface number]

CDP(Cisco Discovery Protocol)

• It is a Cisco proprietary protocol
• Works at layer-2
• Used to find directly connected cisco devices
• Helpful in documenting network diagram

Verify:
RTR # show CDP neighbours
OR
RTR # show CDP neighbours detail