Question

How did CIDR (Classless Inter-Domain Routing) summarization and VLSM (Variable Length Subnet Masks) optimize sub-netting? What are the main issues they came to resolve?

Answer 1

CIDR,VLSM are introduced to use IP addressing in a more efficienty way, inorder to reduce wastage of IP's
they provide greater flexibility in creating subnets
CIDR: a subnet Mask is assigned to IP address, which denotes number of network bits
example of CIDR IP: 10.17.18.0/16
/16 is subnet mask
here 16 bits are for network
last 16 bits are for host
VLSM:it allows to steal bits from host part of an IP to add them to network inorder to create subnets
consider above IP
now, we will take 4 bits from host part
and them to subnet mask
now, new mask is /20
which creates 2^4 = 16 subnets
each has 2^12 hosts in it //since host bits are 12
like wise we can create subnets
this reduces the wastage of IP's