An enterprise network operations team is allocating IPv4 subnets from the parent block 172… — CompTIA Network+

An enterprise network operations team is allocating IPv4 subnets from the parent block $172.31.192.0/19$ to provision Point-to-Point WAN links between datacenter locations. Each link requires a dedicated subnet configured with a $/30$ mask to connect two router interfaces. If the team provisions $45$ operational Point-to-Point link subnets sequentially starting from the lowest IP address of the parent block, what is the maximum number of additional $/30$ link subnets that can be created from the remaining unallocated space within this $/19$ block?

Answer: 2003 subnets

Answer

The maximum number of additional /30 link subnets that can be created from the remaining unallocated space is 2003.

The parent block has a prefix length of /19 and each link uses a /30 subnet mask. Subtracting the prefix lengths (

30 - 19 = 11

) gives

11

subnet bits, which equals

2^{11} = 2048

total possible /30 subnets within the /19 block. Subtracting the 45 already provisioned subnets leaves

2048 - 45 = 2003

unallocated /30 subnets.

Step-by-Step Solution

Calculate the total number of /30 subnets available within a /19 parent block

2048 subnets

The prefix length difference between the child subnet (/30) and parent block (/19) is

30 - 19 = 11

bits. The total number of /30 subnets created is

2^{11} = 2048

Subtract the number of already allocated /30 subnets from the total available subnet capacity

2003 subnets

Subtracting the

45

allocated subnets from the total capacity of

2048

(

2048 - 45 = 2003

) yields the remaining unallocated /30 subnets.

Key Concept

Subnet allocation and capacity calculations using CIDR prefix length differences

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