Subnetting Questions 20 | Calculate Subnet Mask from the IP Address

Subnetting Questions 20

You have a network ID of 134.57.0.0 with 8 subnets. You need to allow the largest possible number of host IDs per subnet. Which subnet mask should you assign?

Solution

Hence, the IP Address starts from 134, it indicates it is a Class B Address. By default, in Class B Address 16 bits are reserved for the network and 16 bits are reserved for the host.

A/Q we need 8 Subnets with the maximum host. It means, we have to borrow 3 bits from the third octet. (2³ = 8 Subnets)

11111111.11111111.11100000.00000000

(2⁷ + 2⁶ + 2⁵ + 2⁴ + 2³ + 2² + 2¹ + 2⁰) . (2⁷ + 2⁶ + 2⁵) . 0 . 0

Therefore, the Subnet Mask is 255.255.224.0

Additional Information:

Hence, 13 bits are available for the host. it means the total number of host on each network is

2ⁿ – 2 (n indicates the total number of host bits. Substracted 2 because on every network, first IP Address is reserved for the network and the last IP Address is reserved for the host)

2¹³ – 2

= 8192 – 2

= 8190 host on each network will be available.

Class B Subnetting Tutorial

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