Subnetting

Question 0

What is a subnet mask?

Answer 0

Subnet mask—A 32-bit combination used to describe which portion of an address refers to the subnet and which part refers to the host.

(Cisco.com)

Question 1

What are some benefits of subnetting?

Answer 1

• Smaller broadcast domains (broadcasts don’t disrupt as many devices).
• Easier to manage multiple smaller subnets than one large network.
• More efficient allocation of IPv4 addresses, which have become scarce.
• You can apply security policies more easily.

Question 2

What is a subnet?

Answer 2

Subnet—A portion of a network sharing a particular subnet address.

(Cisco.com)

Question 3

What is the equation for determining the number of subnets available for a given IP address/subnet mask combination?

Answer 3

2^x where x = the # of bits turned on in (or “borrowed” from) the host portion of the address

Question 4

What is the equation for determining the number of host addresses available for a given IP address/subnet mask combination?

Answer 4

2^y - 2 where y = the number of off bits in the (default) host portion of the subnet mask.

Question 5

How many subnetworks would be available on network 131.64.0.0 255.255.248.0?

Answer 5

32

131 = class B
Class B IP's have a default mask of 16

255.255.248.0

       =

1111111.11111111.11111000::
(/21)

5 bits are borrowed from the host portion.

2^5 = 32