CCIE Security Exam: Identify Subnet for

Which Subnet Does Belong To?

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In what subnet does address reside?



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A. B. C. D. E.


To determine the subnet in which the given address resides, we need to apply the subnetting rules.

The /27 in the address represents the subnet mask, which consists of 27 ones followed by 5 zeros in binary form:


To find the subnet address, we perform a bitwise AND operation between the given address and the subnet mask:

Address: 11000000.10101000.00010111.11000101 ( Mask: 11111111.11111111.11111111.11100000 (/27) Result: 11000000.10101000.00010111.11000000 (

Therefore, the subnet address for the given IP address is

Now we need to determine the range of IP addresses in the subnet. Since the subnet mask is /27, we know that there are 32 - 27 = 5 bits available for host addresses. This gives us a total of 2^5 = 32 possible host addresses in the subnet.

The first address in the subnet is the subnet address itself (, and the last address is the broadcast address ( Therefore, the valid host range for the subnet is -

We can see that the given address falls within this range. Therefore, the subnet in which the address resides is, which is option D in the list of answers.