Subnetting 122.22.0.0 /22 query

black_lion

Hi all. I have been given the address: 122.22.0.0 /22 which in binary is 01111010.00010110.00000000.00000000 (bold is 10 bits left for hosts)

and its subnet mask is 255.255.252.0 in binary is 11111111.11111111.11111100.00000000

I am trying to calculate new subnet address when 8 bits left for host (this is a network prefix of /24)

This is what I did:

122.22.0.0 converted to binary with network prefix of /24 is:

01111010.00010110.00000000.00000000 (bold shows 8 bits left for host)

and in decimal new subnet address from my understanding is 122.22.0.0 /24

but correct answer is 122.22.2.0 /24

Why does the 3rd octet is 2 and not 0?

10Linefigure

If you have a /24 then your entire last octet is open to hosts. Having your /22 allows for 255.255.252.0 so you have 3.254 as your block size, this allows you to break your Vlans and manage IP's much easier then a /8 , /16, /24 because they leave all the rest as host bits and give you less to work with.