IP subnetting

Subnetting part 1
IP address

Subnet address
1st Host address
Last Host address
Broadcast address

Two methods

Method 1 - Binary Method
Method 2 - Quick Method

Typical example

What IP address would router1 be configured with if it is to use the first ip address in the same subnet as PC1?
What broadcast address is use by PC1?
What ip address would Router1 be configured with if it is to use the last IP address in the same Subnet as PC1?
What subnet is PC1 part of?

Binary Rules

Network/subnet address

Fill the host portion of an address with binary 0’s

Broadcast address

Fill the host portion of an address with binary 1’s

First Host

Fill the host portion of an address with binary 0’s except for the last bit which is set to binary 1

Last Host

Fill the host portion of an address with binary 1’s except for the last bit which is set to binary 0

3rd example
172.16.129.1/17

172.16.1|000 0001.0000 0001
subnet = 172.16.1000 0000.0000 0000=172.16.128.0
Broadcast= 172.16.1111 1111.1111 1111=172.16.255.255
1st host=172.16.128.1
last host=172.16.255.254

Shortcut table
128|64|32|16|8|4|2|1
128|192|224|240|248|252|254|255

Tip: the first line shows the decimal values for the binary numbers of an octet
10000000=128 00010000=16

Second row, subtract the value in the frist row from 256
256-128=128 256-32=224 256-64=192 256-1=255

Binary odometer:(0-255)
10.1.1.254+1=10.1.1.255
10.1.1.255+1=10.1.2.0
10.1.2.0+1=10.1.2.1
or in reverse:
10.1.2.0-1=10.1.1.255

Broadcast address = Next Network -1
First host = subnet +1
last host = broadcast -1
What subnet is this host on?
What is a last host?

Subnetting part 2
creat multiple subnets

Subnet this network into at least 10 subnets
Subnet this network into subnets each having 10 host

Azure VMs networking

Priority: the lower the number, the higher the priority.

ipcalc in linux

ipcalc 13.75.0.0/16
Address: 13.75.0.0 00001101.01001011. 00000000.00000000
Netmask: 255.255.0.0 = 16 11111111.11111111. 00000000.00000000
Wildcard: 0.0.255.255 00000000.00000000. 11111111.11111111
=>
Network: 13.75.0.0/16 00001101.01001011. 00000000.00000000
HostMin: 13.75.0.1 00001101.01001011. 00000000.00000001
HostMax: 13.75.255.254 00001101.01001011. 11111111.11111110
Broadcast: 13.75.255.255 00001101.01001011. 11111111.11111111
Hosts/Net: 65534 Class A