The new mask of 255.255.240.0 or /20 leaves 12 bits for hosts. Because 4 bits were borrowed, we can determine that 16 subnets were created because 2 4 = 16. The original subnet mask was 255.255.0.0 or /16. Let’s analyze how this table was completed. IPv4 Address of First Host on this Subnet The following example shows a sample problem along with the solution for solving this problem: Given: When given an IPv4 address, the original subnet mask and the new subnet mask, you will be able to determine: Part 2: Calculate IPv4 Address Subnetting From there, it is a simple calculation:Ģ (number of host bits) – 2 = Number of hostsĭetermine the network and broadcast addresses and number of host bits and hosts for the given IPv4 addresses and prefixes in the following table. Subtracting 18 network bits from 32 bits results in 14 bits left for the host portion. Using our example above, the subnet mask 255.255.192.0 is equivalent to /18 in prefix notation. Subtracting the number of bits used for the network portion (as represented by the subnet mask) gives you the number of bits used for hosts. The subnet mask will be represented in dotted decimal format, such as 255.255.192.0, or in network prefix format, such as /18. Perform binary ANDing on the third octet.Īnalyzing this example again produces the following result:Ĭontinuing with this example, determining the number of hosts per network can be calculated by analyzing the subnet mask. The fourth octet will result in 0 due to the subnet mask. The first two octets will result in 172.30 due to the subnet mask. Knowing this, you may only have to perform binary ANDing on an octet that does not have 255 or 0 in its subnet mask portion.Īnalyzing this example, you can see that you only have to perform binary ANDing on the third octet. If the subnet mask has decimal value 0 in an octet, the result will ALWAYS be 0 for that octet.
Hint: If the subnet mask has decimal value 255 in an octet, the result will ALWAYS be the original value of that octet. REVIEW: To determine the network address, perform binary ANDing on the IPv4 address using the subnet mask provided.
In Part 1, you will determine the network and broadcast addresses, as well as the number of hosts, given an IPv4 address and subnet mask.
Subnet mask table 4 bits Pc#
The public IP addresses used in this lab are owned by Cisco.
Subnet mask table 4 bits how to#
It is suggested that the first problem is done together in class to give students guidance as to how to proceed for the rest of the assignment. If the assignment is done in class, you may wish to have students work alone or in teams of 2 students each. When given an IP address and subnet mask, you will be able to determine other information about the subnet.Īnswers Note: This activity can be done in class or assigned as homework. The first part is designed to reinforce how to compute network IP address information from a given IP address and subnet mask. The ability to work with IPv4 subnets and determine network and host information based on a given IP address and subnet mask is critical to understanding how IPv4 networks operate. Part 2: Calculate IPv4 Address Subnetting Background / Scenario Part 1: Determine IPv4 Address Subnetting Optional activities are designed to enhance understanding and/or to provide additional practice. Last Updated on Januby Admin 8.1.4.6 Lab – Calculating IPv4 Subnets Answers Lab – Calculating IPv4 Subnets ( Answers Version – Optional Lab)Īnswers Note: Red font color or gray highlights indicate text that appears in the instructor copy only.
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