The original subnet mask was 255.255.0.0 or /16. The new subnet mask is 255.255.240.0 or /20. The resulting difference is 4 bits. Because 4 bits were borrowed, we can determine that 16 subnets were created because 24 = 16. The new mask of 255.255.240.0 or /20 leaves 12 bits for hosts. With 12 bits left for hosts, we use the following formula: 212 = 4,096 2 = 4,094 hosts per subnet. – Binary ANDing will help you determine the subnet for this problem, which results in the network 172.16.64.0. Finally, you need to determine the first host, last host, and broadcast address for each subnet. One method to determine the host range is to use binary math for the host portion of the address. In our example, the last 12 bits of the address is the host portion. The first host would have all significant bits set to zero and the least significant bit set to 1. The last host would have all significant bits set to 1 and the least significant bit set to 0. In this example, the host portion of the address resides in the 3rd and 4th octets. Description 1st Octet 2nd Octet 3rd Octet 4th Octet Description Network/Host nnnnnnnn nnnnnnnn nnnnhhhh hhhhhhhh Subnet Mask Binary 10101100 00010000 01000000 00000001 First Host Decimal 172 16 64 1 First Host Binary 10101100 00010000 01001111 11111110 Last Host Decimal 172 16 79 254 Last Host Binary 10101100 00010000 01001111 11111111 Broadcast Decimal 172 16 79 255 Broadcast Fill out the tables below with appropriate answers given the IPv4 address, original subnet mask, and new subnet mask.
The original subnet mask was 255.255.0.0 or /16. The new subnet mask is 255.255.240.0 or /20. The resulting difference is 4 bits. Because 4 bits were borrowed, we can determine that 16 subnets were created because 24 = 16. The new mask of 255.255.240.0 or /20 leaves 12 bits for hosts. With 12 bits left for hosts, we use the following formula: 212 = 4,096 – 2 = 4,094 hosts per subnet. Binary ANDing will help you determine the subnet for this problem, which results in the network 172.16.64.0. Finally, you need to determine the first host, last host, and broadcast address for each subnet. One method to determine the host range is to use binary math for the host portion of the address. In our example, the last 12 bits of the address is the host portion. The first host would have all significant bits set to zero and the least significant bit set to 1. The last host would have all significant bits set to 1 and the least significant bit set to 0. In this example, the host portion of the address resides in the 3rd and 4th octets. Description 1st Octet 2nd Octet 3rd Octet 4th Octet Description Network/Host nnnnnnnn nnnnnnnn nnnnhhhh hhhhhhhh Subnet Mask Binary 10101100 00010000 01000000 00000001 First Host Decimal 172 16 64 1 First Host Binary 10101100 00010000 01001111 11111110 Last Host Decimal 172 16 79 254 Last Host Binary 10101100 00010000 01001111 11111111 Broadcast Decimal 172 16 79 255 Broadcast Fill out the tables below with appropriate answers given the IPv4 address, original subnet mask, and new subnet mask.
9.1.4.8%20Lab%20-%20Calculating%20IPv4%20Subnets.docx