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Zorluk: ZorIPv4 Addressing and Subnetting

A network engineer is partitioning the address block 10.45.160.0/1910.45.160.0/19 to provision a new VoIP network segment that must accommodate at least 500500 IP phones. To prevent address space depletion, the engineer allocates the smallest valid subnet starting at the beginning of the block that satisfies this host capacity requirement. What is the last usable host IP address of this newly allocated subnet?

  1. A
    10.45.161.255
  2. B
    10.45.160.254
  3. 10.45.161.254Cevap
  4. D
    10.45.163.254

Cevap

10.45.161.254
To accommodate at least 500500 usable host addresses with minimal wastage, 99 host bits are needed (292=5102^9 - 2 = 510 usable addresses), establishing a /23/23 subnet mask. The first /23/23 subnet within 10.45.160.0/1910.45.160.0/19 ranges from 10.45.160.010.45.160.0 (Network ID) to 10.45.161.25510.45.161.255 (Broadcast Address). Subtracting 11 from the broadcast address yields 10.45.161.25410.45.161.254 as the final usable host IP address.

Adım Adım Çözüm

1
Determine the required host bits and CIDR prefix length
9 host bits are required, yielding a /23 subnet prefix
The formula for usable hosts is 2h25002^h - 2 \ge 500. For h=8h = 8, 282=2542^8 - 2 = 254 (insufficient). For h=9h = 9, 292=5102^9 - 2 = 510 (sufficient). The prefix length is 329=2332 - 9 = 23.
2
Calculate the network block boundaries for the first /23 subnet
Network ID: 10.45.160.0/23, Broadcast Address: 10.45.161.255
A /23 subnet has a block size of 22 in the third octet (256254=2256 - 254 = 2). Starting at 10.45.160.010.45.160.0, the network spans from 10.45.160.010.45.160.0 through 10.45.161.25510.45.161.255.
3
Identify the last usable host IP address within the subnet boundary
10.45.161.254
The last usable host IP address is always one numeric value below the broadcast address (10.45.161.2551=10.45.161.25410.45.161.255 - 1 = 10.45.161.254).

Anahtar Kavram

Subnet Host Capacity and Subnet Boundary Calculation
Tahmini Süre:2m 0s
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