IPv4 Addressing (Part 2)

IPV4 address classes

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

Maximum Hosts per Network

Host portion all 0s = Network address (network ID) Host portion all 1s = broadcast address

192.168.1.0/24 -> 192.168.1.255/24 Host portion = 8 bits = 2^8 = 256 Maximum hosts per network = 2^8-2 = 254

172.16.0.0/16 -> 172.16.255.255/16 Host portion = 16 bits = 2^16 = 65,536 Maximum hosts per network = 2^16 -2 = 254

10.0.0.0/8 -> 10.255.255.255/8 Host portion = 24 bits = 2^24 = 16,777,216 Maximum hosts per network = 2^24 -2 = 16,777,214

Formula

maximum host per network = 2^n-2 
(n=number of hist bits)

First/last usable address

192.168.1.0/24 ---------> 192.168.1.255/24 00000000 11111111 00000001 11111110 192.168.1.1/24 192.168.1.254/24 = first usable address = last usable address

Cisco router command

For all the interface info

R1#show ip interface brief

Interface           IP-address  OK?   Method  Status                Protocol
GigabitEthernet0/0  Unassigned  YES   unset   adminstratively down  down

adminstratively down: Interface has been disabled with the shutdown command
This is the default Status of Cisco router interfaces.
Cisco switch interfaces are NOT administratively down by default
Status = Layer 1 status (is there a cable)
Protocol = Layer 2 status (is ethernet function conrectly)

enter the configuration mode for the interface

// shortcut for configuration terminal
R1#conf t
// for configuration of the interface
R1#interface gigabitethernet 0/0
//shortcut
R1#in g0/0

setting the ip adress

R1#ip address 10.255.255.254 255.0.0.0
//enable the interface
R1#no shutdown
// view the change
R1#do show ip interface brief
// shortcut version
R1#do sh ip int br

show interfaces

to see all the details of the interface

R1#show interfaces g0/0

descriptions of an interface

// see all the description
R1#show interfaces description
// for assigning a description 
// swithc to configuration interface
R1#int g0/0
R1# description ## to SW1 ##

Review

IPV4 address classes (review clarification)
Finding the maximum number of hosts, network address, broadcast address, first usable address, last usable address of a particular network
Configuring IP addresses on Cisco device

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