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SK0-004 · Question #102

A server administrator has been given the following information from the network team in order to configure IP addresses on a new server: Network Address: 199.90.10.32/28 The network team also…

The correct answer is C. 199.90.10.47, 255.255.255.240. A /28 prefix means 28 network bits and 4 host bits, giving a subnet mask of 255.255.255.240 (block size = 256 − 240 = 16). Starting from 199.90.10.32, the subnet spans .32 to .47: .32 is the network address and .47 is the broadcast address, leaving .33–.46 as usable hosts. The…

Server administration

Question

A server administrator has been given the following information from the network team in order to configure IP addresses on a new server:

Network Address: 199.90.10.32/28 The network team also instructed the server administrator to use the LAST usable address on the given network. Which of the following IP address/subnet mask combinations should the server administrator use?

Options

  • A199.90.10.49, 255.255.255.240
  • B199.90.10.47, 255.255.255.224
  • C199.90.10.47, 255.255.255.240
  • D199.90.10.48, 255.255.255.240

How the community answered

(17 responses)
  • A
    6% (1)
  • B
    24% (4)
  • C
    59% (10)
  • D
    12% (2)

Explanation

A /28 prefix means 28 network bits and 4 host bits, giving a subnet mask of 255.255.255.240 (block size = 256 − 240 = 16). Starting from 199.90.10.32, the subnet spans .32 to .47: .32 is the network address and .47 is the broadcast address, leaving .33–.46 as usable hosts. The last usable host is 199.90.10.46; however, option C (.47 with 255.255.255.240) is the only choice with the correct /28 subnet mask and within the correct subnet range. Options A and D (.49 and .48) fall in the next subnet, and option B uses the wrong mask (255.255.255.224 = /27).

Topics

#IP addressing#subnetting#CIDR notation#usable host addresses

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