Cisco IOS Basics

In cisco switches 6 lights are at the left (for example 3550 series)
 

There is a mode button at the left,pushing that will take us to another mode in six modes. 
 

1.system:first the green will blink and after it started properly the green light stays on,if the light is amber give the switch back. 
 

2.RPS(Redundant Power Supply):Some switches have multiple power supply in case one got bad.If the redundant power supply us connected to power the green light will be on. 
 

3.STAT:shows status of the port,if something is connected to the port it will be green,some port will blink if its having some network activity ,if nothing plugged in the stat will be dark.

4.UTIL:utilization which constantly monitors the the utilization of the ports.

5.DUPLEX:checks if full duplex is configured. 
 

6.SPEED:checks if the port is 100 mb/s or 10mb/s.The light is on for 100 and not on for 10.
 

When a switch boots up(here for example 3550 series) 
 

the post operation(power on self test)starts
 

It shows the base mac address 
 

Shows information about the flash bios system where it stores the ios 
 

It basically copy the flash in ram and uncompress it 
 

Then you can see some copyright information 
 

Then the model of the switch 
 

Then the version of the ios 
 

Then will check every component inside it the processor,the memory,the interfaces 
 

When it show its memory it will basically devide the whole memory in separate chunks as all cisco devices,so the whole memory would be the summation of those for example 65526k/8192k 
 

Then it shows what kind of switching image you are running (if it's layer 2/3 or compatible with both layer 2 and 3) 
 

Then shows the interfaces  
 

Then summarizes the interfaces. For example
24 fast ethernet interfaces/IEEE 802.3 interface(s)
2 Gigabit Ethernet/IEEE 802.3 interface(s)

Then shows how much nvram(non-volatile memory)it has for example 384K bytes of flash-simulated non-volatile configuration memory 
 

Then comes the intial config dialog box 
 

just type n  and press enter

Type en to enter the exec mode abd then type conf t to enter the global mode 
 

? for help

to set a hostname 

from flobal config mode

hostname devicename 

 

There are 3 modes

User mode ,privileged mode or exec mode, global configuration mode 
 

To get back to exec mode

Type end or exit or ctrl + z 

 

Error code ambiguous command means it's right but still need to be defined more 
 

Error code invalid input detected means command is wrong 
 

From exec mode type show history to see all commands 
 

ctrl + e moves cursor to the end of the line 
 

ctrl + a moves cursor to beginning of the line 
 

To give switch an ip 
 

By default every port in a switch is in vlan1 
 

So we have to create a virtual interface named interface vlan 1(doesn't exist physically)

Every device on vlan 1 are now able to access it and we can access the switch remotely using this ip 
 

To configure interface vlan 1 
 

In global config mode

Type 
 

interface vlan 1
ip address 192.168.1.1 255.255.255.0(just an example)
no shutdown(no basically negates a command to reverse it's effect for example no hostname negates the hostname that you put in ur switch and changes the hostname to the previous one)

exit 

 

To see an interface 
 

In the exec mode 
 

type 

sh int vlan 1

now we have to give the switch a gateway address so that it can go in different network 
 

go in the global mode 
 

Type 
 

ip default-gateway 192.168.1.254 

 

Now to see the running configuration

From exec mode 
 

show running-config or sh run 
 

To save the configuration from ram to nvram

copy running-config startup-config 

 

To see the startup configuration 
 

From exec mode 
 

show startup-config 

 

To see the basic information about switch 
 

From exec mode 
 

Type
 

show version