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Last Updated: May 1, 2023 Fact Checked

## Using a Network Calculator

Converting to binary, using classful network, classful network examples, cidr examples.

This article was co-authored by wikiHow staff writer, Travis Boylls . Travis Boylls is a Technology Writer and Editor for wikiHow. Travis has experience writing technology-related articles, providing software customer service, and in graphic design. He specializes in Windows, macOS, Android, iOS, and Linux platforms. He studied graphic design at Pikes Peak Community College. This article has been fact-checked, ensuring the accuracy of any cited facts and confirming the authority of its sources. This article has been viewed 783,683 times. Learn more...

## Things You Should Know

• To get the network and broadcast addresses without doing math, use a network calculator .
• The easiest way to calculate the broadcast and network addresses manually is to convert to binary and count the bits.
• For a classless network, use the CIDR method to subnet your network.

• For example, if the IP address is 192.168.1.3, the binary address is 111000000.10101000.00000001.00000011.
• If the subnet mask is 255.255.224.0, which is /19 in CIDR notation, the binary address would be 11111111.11111111.11100000.00000000.
• We will use the /19 example in this method.

• 11111111.11111111.111 (network) 00000.00000000 (host)
• If you were working with a /24 network, you'd count the first 24 bits (digits) instead. For a /8 network, you'd count the first 8 bits, etc.

• For the binary IP address 11000000.10101000.00000001.00000011, 11000000.10101000.000 , the first 19 digits, is the network. The remaining 13 digits, 00001.00000011 , represents the host.

• Network address: The first 19 bits from the IP address with the last 13 bits of the subnet mask: 11000000.10101000.000.00000.00000000
• Converted: 192.168.0.0

• Last 13 bits of subnet mask as ones: 11111.11111111
• Converted: 192.168.0.31

• Subnet masks can be 0, 128, 192, 224, 240, 248, 252, 254 and 255.
• The number of bits used for subnetting (n) to their corresponding subnet mask is as follows: 0=0, 128=1, 192=2, 224=3, 240=4, 248=5, 252=6, 254=7, and 255=8.
• Subnet mask 255 is default, so it'll not be considered for subnet masking.
• For example: Let's assume the IP address is 210.1.1.100 and Subnet mask is 255.255.255.224. The total bits= T b = 8. The number of bits used for subnetting for subnet mask 224 is 3.

• Using the example above, n=3. The number of bits left for host is (m) = 8 - 3 = 5. 5 is the number of bits you have left to host.

• In our example, the number of subnets is 2 n = 2 3 = 8. 8 is the total number of subnets.

• In our example, the value of last bit used for subnet masking is Δ = 2 5 = 32. The value of the last bit used is 32.
• 5 Calculate the number of hosts per subnet. The number of hosts per subnet is represented by the formula 2 m - 2 .

• The 8 subnets (as calculated in previous step) are shown above.
• Each of them has 32 addresses.

• Example: If the bit-length prefix is 27, then write it as 8 + 8 + 8 + 3 .
• Example: If bit-length prefix is 12, then write it as 8 + 4 + 0 + 0 .
• Example: Default bit-length prefix is 32, then write it as 8 + 8 + 8 + 8.

• Using another example, the IP address is 170.1.0.0/26 . Using above table, you can write the bit-length prefix 26 as 8+8+8+2. Using the chart above, this converts to 225.225.225.192. Now the IP address is 170.1.0.0 and subnet mask in quad-dotted decimal format is 255.255.255.192 .
• 3 Determine the total number of bits. The total number of bits is represented using the following equation: T b = 8 .

• For subnet mask 255 is default, so it'll not consider for subnet masking.
• From the previous step, you got IP address = 170.1.0.0 and Sub-net mask = 255.255.255.192
• Total bits = T b = 8
• Number of bits used for subnetting = n. As the subnet mask = 192, its corresponding number of bits used for Subnetting is 2 from above table.

• In our example, the number of bits used for subnetting (n) is 2. So the number of bits left for host is m = 8 - 2 = 6. The total bits left for the host is 6.
• In our example, the number of subnets = 2 2 = 4. The total number of subnets is 4.

• In our example, the value of last bit used for subnet masking = Δ = 2 6 = 64. The value of the last bit used for subnet masking is 64.

• In our example, the last value used for subnet masking is 64. This produces 4 subnets with 64 addresses.

• See CIDR Examples for more examples.
• 4 See Classful Network Examples for more examples.

IP address = 200.222.5.100 and subnet mask = 255.128.0.0 Total bits = T b = 8

Number of bits used for subnetting for subnet mask 128 = n 1 = 1 (as subnet mask = 128 and its corresponding "No. of bits used for Subnetting" is 1 from above table)

• 2 Number of bits left for host for subnet mask 128 = m 1 = T b - n 1 = 8 - 1 = 7 Number of bits left for host for subnet mask 0 = m 2 = m 3 = T b - n 2 = T b - n 3 = 8 - 0 = 8 Number of subnets for subnet mask 128 = 2 n 1 = 2 1 = 2 Number of subnets for subnet mask 0 = 2 n 2 = 2 n 3 = 2 = 1 Value of last bit used for subnet masking for subnet mask 128 = Δ 1 = 2 m 1 = 2 7 = 128 Number of host per subnet = 2 m 1 - 2 = 2 7 - 2 = 126 Value of last bit used for subnet masking for subnet mask 0 = Δ 2 = Δ 3 = 2 m 2 = 2 m 3 = 2 8 = 256 Number of host per subnet for subnet mask 0 = 2 m 2 - 2 = 2 m 3 - 2 = 2 8 - 2 = 254

## Community Q&A

• In CIDR, just after you convert the bit-length prefix to quad-dotted decimal format, you can follow the same procedure as for Classful network. Thanks Helpful 0 Not Helpful 0
• This method is only for IPv4, not applicable for IPv6. Thanks Helpful 0 Not Helpful 0

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The broadcast address can be used to send data packets in IP networks to all participants of a local network. The individual addresses of each party in the network do not have to be known for this to work. If necessary, the broadcast address can be calculated quite easily.

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Each network or subnet has a reserved broadcast address that can be used by all participants of the network to send a broadcast . Broadcasts allow information and services to be transmitted to all devices and components of the network without the need to know their individual IP addresses . Among other things, routers in a local area network use the broadcast IP to send HELLO packets to all endpoints, switches, and other routers to maintain interrelationships on the network and discover neighboring devices.

Broadcast: a multipoint connection in IP networks that automatically reaches all nodes in the network without knowing the recipient addresses. For this purpose, a fixed reserved broadcast address exists in each network or subnet.

Each IP address consists of 4 decimal numbers — so-called octets — separated by dots. An octet contains 8 bits, which is why every IPv4 address is automatically a 32-bit address. Each octet can represent a number between 0 and 255. The broadcast address is always identified in the final part of the host part of an address (starts in the third or fourth octet): If all host bits are set to the binary value “1”, this is the broadcast address.

If all host bits are set to the value “0”, this is the subnet address.

The following example is intended to clarify the composition of the individual components of an IP address, including the calculation of the broadcast address:

192.128.64.7 is the IP address in this case, while the suffix “/24” indicates the subnet mask 255.255.255.0 .

In each network, a broadcast IP is assigned only once . It is always the last IP address of the subnet. The broadcast address — where all host bits are set to “1” as already mentioned — is therefore: 192.128.64.255 in this example.

You want to find out the broadcast address of your network? For this, common operating systems with native command line applications and the network program ipconfig (Windows) or “ifconfig” or “ip” (Linux, macOS) provide the appropriate tool set.

In Windows , for example, proceed as follows:

• Start the command prompt by using the key combination [Windows] + [R] and execute the command “ cmd ”.
• Enter the CMD command “ ipconfig /all ” into the command line tool to get an overview of all important key data of your local network.

Among other things, the prompt presents you with your device’s IP address and subnet mask. You can derive the broadcast IP from this information. In our example where the IP address is 192.168.2.34 and the subnet mask is 255.255.255.0 , the broadcast address is 192.168.2.255 .

How exactly you find out the broadcast address in Linux and macOS depends on the available network tool of the respective distribution or version. In Ubuntu 20.04 , for example, you can proceed as follows:

• Open the “ Show applications ” menu.
• Search for “ Terminal ” and start the application by double-clicking on it.
• Enter the command “ ifconfig ”.

Right in the second line , Ubuntu presents three values after executing the command:

• inet : the Internet address of your device (here: 172.18.166.193 )
• netmask : the subnet mask of the local network (here: 255.255.250.0 )
• Encyclopedia

## Network types at a glance

When several computers are connected to one another it is known as a network. Networks enable data exchange between different devices, making shared resources available. Different network types are implemented depending on which transmission techniques and standards are used. These differ in terms of the number of connected systems and potential reach.

## PPPoE: DNS protocol

How exactly do you access the internet? Those who have a DSL contract, for example, first have to contact their internet provider’s node each time they connect. The provider checks the access authorization and establishes the connection to the internet. The so-called “Point-to-Point Protocol over Ethernet” (PPPoE) is used for this purpose. But how exactly does this protocol work?

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• 1 You may want to use non-default address for broadcasting... for example if you want to allow your broadcasts to be routed to another subnet. What's the reason for that can be - I don't know. –  Akina Aug 1, 2018 at 6:58

The broadcast address is configurable by hand mostly because it is a good practice to allow the user to have more flexibility and freedom about what they want to configure.

Besides that, there are two reasons I could think of, that would need a manually configured broadcast address.

IP Directed Broadcasts : These are broadcast packets directed to an external (remote) network. You can send a broadcast packet to that network's broadcast address and the router that is the network's gateway will transform it into a Layer 2 broadcast frame and forward it to all hosts in the network. However, these directed broadcasts are usually disabled by default, since they could be used in a malicious way, e.g., smurf attacks , DoS attacks, and more.

UDP Broadcast Packet Forwarding : By default routers break the broadcast domain. However, since services like DHCP work by using broadcast packets, routers can be configured to forward broadcast packets to a specific address. This could be the DHCP server's address, another host on the network, or this can even be an IP Directed Broadcast address .

These are two cases where you'd need a manually configured broadcast address. The second case being for a router, though, but nonetheless, it works for a normal host depending on its configuration. This is not applicable to all routers, example is given for Cisco routers.

Not the answer you're looking for browse other questions tagged networking ip ..

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## .itprclogo_0{fill:#1D93D1;} .itprclogo_1{fill:#0993D2;}

Imagine you’re Paul Revere, riding from Boston to Lexington to warn citizens that the redcoats were coming. He may not be as fast as computer networks today, but Paul Revere was essentially acting much like a broadcast would- he was relaying his message to the entire town of Lexington.

A broadcast, in particular, is a simple message that is sent to all clients on a local area network. But just exactly what enables a network to broadcast a message to every single client on the network?

A broadcast address is an address used to indicate that information being sent out should be delivered to every client on the local area network. These addresses are always the highest number possible in a particular network address or subnet. We’ll cover subnets later, for now let’s take a closer look at the most common broadcast address: Data Link Layer broadcasts.

Broadcasts on the Data Link Layer correspond to MAC addresses. MAC address broadcasts are generally the easiest to understand, since they aren’t affiliated with IP addresses or subnetting. In fact, all you really need to remember is FF:FF:FF:FF:FF:FF. Whereas this MAC address would normally be comprised of different hexadecimal values, it is instead simply all F’s. (As we know, each F stands for the highest number in hexadecimal: 15)

When a MAC address broadcast is sent out, each network interface card on the local area network will see the broadcast address and automatically pass the information up to the upper layers of the OSI model. So far it’s simple- right? Now let’s get back to the subnetting and IP address topics that are present on the Network Layer.

## How IP Broadcasts are Sent via the Network Layer

Remember how we stated that broadcast addresses are always the highest-most number in an address range? IP broadcasts are no exception! On a network that isn’t subnetted, we can simply place 1’s in place for each bit in the host portion. The result: our very own broadcast address!

Things are still fairly simple: simply replace each host portion with the highest number you can create with 8 bits: 255. Notice that the network portions do not change- just the host portions.

Sadly, this is where things start to get a little trickier: we need to find the broadcast address of a subnetted network.

We need two things to find the broadcast address of a subnetted network: an IP address, and the subnet mask. The process is simple: find the inverse of the subnet mask. Then take the result, and logically OR it with the IP address to get the broadcast address.

Of course, we can convert the above binary result to decimal and get the broadcast address of 192.168.16.31. If you aren’t familiar with the OR process, it’s rather simple. If there is a 1 in either the IP or subnet field, then the result will always be a 1. (Otherwise, the result is 0)

Now we know how to find the broadcast address and how it works- but what is it used for?

Broadcasts are generally used for several reasons:

• Address Resolution Protocol (ARP) uses broadcasts to map physical addresses to logical addresses. To build the table of hosts, a device needs to send a broadcast to every other device on the network to essentially find out who is where.
• Several types of network protocols and services use broadcasts in the same way. Dynamic Host Configuration Protocol (DHCP), for instance, requires that broadcasts be used to dynamically assign an IP address to computers on a network.
• Routing protocols such as Routing Information Protocol (RIP) use broadcasts to send out “advertisements.” This advertisement is used by routers to map out the topology of a network, so that data can be routed to the appropriate place accordingly. (Interesting enough, this protocol will attempt to find the fasted route through a network to a destination, based on how many “hops” it takes to get from the sender to the receiver.)

## Final Points of Interest on Broadcasts

Keep in mind that broadcasts will travel to every single client on a network- at least, until a router is encountered. A router is the only device that can separate a broadcast domain. Logically, this is mandatory for the internet to exist. What do you think would happen if broadcasts were being sent from network to network- all over the internet? (Hint: no more Internet.)

Also make note that broadcast addresses should never be used as host addresses. This can be confused in subnetting, where it isn’t always clear where the host portion starts and ends. The broadcast address is reserved as the highest value- and likewise, no IP address should use a broadcast address or problems will arise.