Question 108 - PCCET discussion

To maximize the use of a network address, the administrator should use the subnet that can accommodate the required number of hosts with the least amount of wasted IP addresses. The subnet mask determines how many bits are used for the network portion and the host portion of the IP address. The more bits are used for the network portion, the more subnets can be created, but the fewer hosts can be assigned to each subnet. The formula to calculate the number of hosts per subnet is

2(32n)2

, where n

is the number of bits in the network portion of the subnet mask. For example, a /30 subnet mask has 30 bits in the network portion, so the number of hosts per subnet is

2(3230)2=2

. A /25 subnet mask has 25 bits in the network portion, so the number of hosts per subnet is

2(3225)2=126

.

The subnet 192.168.6.0/25 can accommodate 126 hosts, which is enough for the network with 120 hosts. The subnet 192.168.6.168/30 can only accommodate 2 hosts, which is not enough. The subnet 192.168.6.160/29 can accommodate 6 hosts, which is also not enough. The subnet 192.168.6.128/27 can accommodate 30 hosts, which is enough, but it wastes more IP addresses than the /25 subnet. Therefore, the best option is B. 192.168.6.0/25.

Reference:

Getting Started: Layer 3 Subinterfaces - Palo Alto Networks Knowledge Base

DotW: Multiple IP Addresses on an Interface - Palo Alto Networks Knowledge Base

Configure NAT - Palo Alto Networks | TechDocs