Networking contd
Any device connected to a network will get an ip address which is a unique id to access that device
An Ipaddress can be public or private
public ip (unique globally)
private ip (unique within network)
Our discussion will be on private network so private ip’s primarily
IP Address = network id + host id
IP Address are of two formats
IPv4:
ip address is a 32 bit number which is divided into 4 parts (octect) x.x.x.x
each octet will have 256 numbers ranging from 0 to 255
ipv4 range is 0.0.0.0 to 255.255.255.255
IPv6:
ip address is 128 bit number
To determine what is network id and what is host id we need subnet masks
Examples
## 1
ip: 10.0.1.7
sm: 255.255.255.0
nid: 10.0.1
hid: 7
## 2
ip: 10.0.1.7
sm: 255.255.0.0
nid: 10.0
hid: 1.7
network id is constant for every device in the network and host id is variable, this determines the size of network.
size of network = 2 ^ (n) – 2
n = number of host id bits
we subtract from 2 because
all zeros is network id
all ones (255) is broadcast id
Examples
## 1
ip: 10.0.1.7
sm: 255.255.255.0
nid: 10.0.1
hid: 7
hid size = 1 octect = 8 bits
size = 2^8 - 2 = 256 - 2 = 254
## 2
ip: 10.0.1.7
sm: 255.255.0.0
nid: 10.0
hid: 1.7
hid size = 2 octets = 16 bits
size = 2^16-2 = 65536 - 2 = 65534
## 3
ip: 10.0.1.7
sm: 255.0.0.0
nid: 10
hid: 0.1.7
hid size = 3 octects = 24 bits
size = 2^24 -2 = 16777216 - 2 = 16777214
I want a network to connect 500 devices
size = 500
2 ^n - 2 ~ = 500
valid values of n = 8, 16, 24
in this case lets go with 16
n = 16 = 2 octects for host id
sm = 255.255.0.0
CIDR (Classless Interdomain routing was introduced). All clouds use CIDR to define network ranges
CIDR
look at ip address as bits not octets
lets go with the example
ip: 10.0.1.7
SM: 255.255.255.0 (older)
SM: 11111111.11111111.11111111.00000000
hostid : will have sequence of 1’s in SM
network id: will have sequence of zeros
I want a network with 500 devices
2 ^ n - 2 = 500
valid values of n are any where between 2 to 31
2^n ~= 500
n = 9
hid bits = 9
nid bits = 32 - 9 = 23
SM: 11111111.11111111.11111110.00000000
255.255.254.0
I want a network with 100 devices what is SM
2^n - 2 ~ = 100
2^n ~= 100
n = 7
hid bits = 7
nid bits = 32 - 7 = 25
SM: 11111111.11111111.11111111.10000000
255.255.255.128
I want a network of size 2000 devices find the subnet mask
2 ^ n -2 ~= 2000
n = 11
hid bits = 11
nid bits = 32 - 11 = 21
SM: 11111111.11111111.11111000.00000000
255.255.248.0
CIDR is represented as x.x.x.x/N
N = number of network id bits
Expand CIDR 10.0.0.0/24:
ip: 10.0.0.xxxxxxxx
ip: 10.0.0.00000000 = 10.0.0.0
ip: 10.0.0.11111111 = 10.0.0.255
SM: 11111111.11111111.11111111.00000000
range: 10.0.0.0 to 10.0.0.255
ip: 10.xxxxxxxx.xxxxxxxx.xxxxxxxx
ip: 10.00000000.00000000.00000000 = 10.0.0.0
ip: 10.11111111.11111111.11111111 = 10.255.255.255
SM: 11111111.00000000.00000000.00000000
Expand CIDR: 172.16.0.0/12
ip 172.0001xxxx.xxxxxxxx.xxxxxxxx
ip: 172.00010000.00000000.00000000 = 172.16.0.0
ip 172.00011111.11111111.11111111 = 172.31.255.255
SM: 11111111.11110000.00000000.00000000
Expand CIDR: 192.168.128.0/18
ip: 192.168.10xxxxxx.xxxxxxxx
ip: 192.168.10000000.00000000 = 192.168.128.0
ip: 192.168.10111111.11111111 = 192.168.191.255
SM: 11111111.11111111.11000000.00000000
