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Zorluk: ZorIPv4 Addressing and Subnetting

A network administrator is evaluating the IPv4 configuration on a core router interface assigned the IP address 172.31.223.254/22172.31.223.254/22. Which of the following statements regarding this IPv4 addressing assignment are correct? (Select TWO.)

  1. The configured interface IP address represents the last usable host IP address within the subnet.Cevap
  2. The IP address falls within the RFC 1918 private IPv4 address space.Cevap
  3. C
    The subnet provides a maximum capacity of 1,0241,024 usable host IP addresses for connected endpoints.
  4. D
    The IP address is a globally routable public address because the Class B private space ends at 172.30.255.255172.30.255.255.

Cevap

The statements confirming that the configured interface IP address is the last usable host within the subnet and that the IP address belongs to the RFC 1918 private IPv4 space are correct.
The subnet mask 255.255.252.0 (/22) creates subnets in increments of 4 in the third octet. For 172.31.223.254, the network address is 172.31.220.0 and the broadcast address is 172.31.223.255. Therefore, 172.31.223.254 is the last assignable host address in the subnet. Furthermore, RFC 1918 specifies the Class B private range as 172.16.0.0 to 172.31.255.255, so this address is a valid private IPv4 address.

Adım Adım Çözüm

1
Determine host bits and total/usable address capacity for a /22 prefix.
A /22 prefix leaves 32−22=1032 - 22 = 10 host bits. Total addresses = 210=1,0242^{10} = 1,024. Usable host capacity = 210−2=1,0222^{10} - 2 = 1,022 host addresses.
Network ID and broadcast ID cannot be assigned to individual endpoints.
2
Calculate subnet network boundaries for 172.31.223.254/22172.31.223.254/22.
The subnet mask is 255.255.252.0255.255.252.0. The third octet block size is 256−252=4256 - 252 = 4. Multiplying by 55 yields 55×4=22055 \times 4 = 220. The network ID is 172.31.220.0/22172.31.220.0/22, and the broadcast address is 172.31.223.255172.31.223.255.
Finding the block size in the interesting octet identifies the network boundary and broadcast address.
3
Determine the usable host IP address range.
The usable range is 172.31.220.1172.31.220.1 through 172.31.223.254172.31.223.254. Thus, 172.31.223.254172.31.223.254 is the last assignable host address.
Usable host addresses lie strictly between the network ID and the broadcast ID.
4
Verify RFC 1918 private address range compliance.
RFC 1918 designates 172.16.0.0/12172.16.0.0/12 (172.16.0.0−172.31.255.255172.16.0.0 - 172.31.255.255) as private space. 172.31.223.254172.31.223.254 falls directly within this block.
Checking official RFC 1918 prefix allocations determines public versus private status.

Anahtar Kavram

IPv4 subnet boundary calculation, usable host calculation (2n−22^n - 2), and RFC 1918 private IP address range boundaries.
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IPv4 Addressing and Subnetting

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