IPv4 Address

Done

Address

It is 32 bits (4 bytes) long

The “/” after the IP Address, for example: 192.168.0.1/24, says that from left to right: 24 bits represent the Network portion and 8 bits (the rest) represent the Host portion. The Network portion can count how many networks can be created and the Host portion how many clients can have their own IP Address

Classes

Class	First octet	First Octet range	Prefix Length
A	0xxxxxxx	0-127	/8
B	10xxxxxx	128-191	/16
C	110xxxxx	192-223	/24
D	1110xxxx	224-239
E	1111xxxx	240-255

Class D is for Multicast Address and Class E is reserved for experiments.

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Loopback Addresses: 127 in the first octet is used when referring to the device itself. So it can be 127.xxx.xxxx.xxx

Net mask

It is the same as the prefix length, but it uses a different representation: dotted decimals.

Prefix Length	Net Mask
/8	255.0.0.0
/16	255.255.0.0
/24	255.255.255.0

Network Address

It is the first address of a network. It is identified when all the Host portions are zeros. It cannot be assigned to hosts.

Examples: 192.168.1.0 118.0.0.0 150.178.0.0

Broadcast Address

It is the last address of a network. It is defined when all hosts portions are represented by 255. It cannot be assigned to hosts.

Examples: 192.168.1.255

Router Configuration

Show interfaces

enable
show ip interface brief

This commands lists information about each interface in a router

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Note: Administratively down means that the command shutdown has been applied to an interface disabling it, but in Cisco routers, such status is applied buy default. This doesn`t happen by default on Cisco switches

Interfaces in full details

show interfaces description

show interfaces g0/0 //show interfaces {interface-name}

Description in interfaces

interface g0/0 //interface {interface-name}
description ##to SW1## //description {description}

Select Interface

Option #1

configure terminal #enter Global Config Mode
interface gigabitethernet 0/0 //interface {interface-name}

Option #2

configure terminal
in g0/0

Set the Interface`s IP Address

ip address 10.255.255.254 255.0.0.0 //ip address {ip-address} {subnet mask}
no shutdown //enables the interface by cancelling the shutdown command with "no"