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Zorluk: OrtaIPv4 Addressing and Subnetting

A network technician is verifying the IP configuration of a database server assigned the IP address 172.28.137.95/21172.28.137.95/21. Which of the following represents the broadcast address for the subnet to which this server belongs?

  1. 172.28.143.255172.28.143.255Cevap
  2. B
    172.28.137.255172.28.137.255
  3. C
    172.28.144.255172.28.144.255
  4. D
    172.28.136.255172.28.136.255

Cevap

The broadcast address for the subnet is 172.28.143.255172.28.143.255.
For a /21/21 network prefix, the subnet mask is 255.255.248.0255.255.248.0. The block size in the third octet is 256−248=8256 - 248 = 8. Multiples of 8 in the third octet include 136 and 144, placing IP address 172.28.137.95172.28.137.95 within the 172.28.136.0/21172.28.136.0/21 subnet. The broadcast address is one address prior to the start of the next subnet (172.28.144.0172.28.144.0), which is 172.28.143.255172.28.143.255.

Adım Adım Çözüm

1
Determine the subnet mask and block size for a /21/21 prefix.
A /21/21 CIDR prefix corresponds to subnet mask 255.255.248.0255.255.248.0. The third octet block size is 256−248=8256 - 248 = 8.
The prefix length determines how bits are split between network and host portions.
2
Calculate the network ID for IP address 172.28.137.95172.28.137.95.
The third octet value 137137 divided by 88 gives 17.12517.125. Multiplying 17×8=13617 \times 8 = 136. The network ID is 172.28.136.0/21172.28.136.0/21.
Network boundaries occur at multiples of the block size (0,8,16,…,136,1440, 8, 16, \dots, 136, 144).
3
Calculate the broadcast address of the network segment.
The next subnet begins at 172.28.144.0172.28.144.0. Subtracting 1 IP yields the broadcast address 172.28.143.255172.28.143.255.
The broadcast address is the highest IP address in the subnet range.

Anahtar Kavram

IPv4 CIDR Subnetting and Broadcast Address Calculation
Tahmini Süre:1m 30s
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