sub-netting and LAN

[abprataps]

why do we do sub-netting? what is its primary goal in network? we do sub-netting to group like users or to optimize use of IP?
what role sub-netting play in LAN?

anyone please help me answering above questions.

thanks is advance!

[Georg Pauwen]

Hello,

the primary goal of subnetting is indeed to optimize the use of available IP addresses.

As an example, take 172.16.0.0/16. If you leave this at the /16 mask, that would give you only 1 subnet with 65534 hosts.  If you change the mask to /24, that would give you 256 subnets with 254 hosts each.

Another example would be IP addresses given out by ISPs. These are often /31 addresses, e.g. 202.202.202.112/31. That subnet has only two addresses, 112 and 113.

[Reza Sharifi]

Subneting provide segmentation.  so, in a LAN environment you can have multiple groups (accounting engineering, finance, etc..). So, let say you want accounting to talk to engineering but not finance, you can easily do that by blocking one segment/subnet from the others.  There also times you want to apply a policy to only one group and not all.  So, if you have everyone in the same subnet, that policy will apply to all versus only to a segment.

HTH