ITPEC FE Morning April 2020 Question 34

Source exam: ITPEC FE Morning April 2020Topic: Networks

ITPEC FE Morning April 2020 — Question 34 of 80

Subnet Network Address — find the network address using bitwise AND with the subnet mask.

Given IP = 10.170.70.19, Mask = 255.255.255.240:

  • First three octets: 10.170.70 — unchanged (mask is 255)
  • Last octet: 19 AND 240
  • 19 = 00010011
  • 240 = 11110000
  • AND = 00010000 = 16

Result: 10.170.70.16

Why not others:
- (a) 10.170.70.0 — would require mask 255.255.255.0 (/24)

- (c) 10.170.70.31 — this is the broadcast address of the subnet (16 + 15)

- (d) 10.170.70.255 — broadcast for a /24 network

Key rule: Network address = IP AND subnet mask (bitwise). For mask 240 (/28), the last 4 bits are host bits, giving 16 addresses per subnet (0, 16, 32, 48...).

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