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Get all IP addresses from a given IP address and subnet mask

In Java, I need to get a list of all the IP addresses contained in this IP network.

For example, let netowork be: 192.168.5.0/24, then the output will be (192.168.5.0 ... 192.168.5.255).

I could think of the next method, but it looks dirty, is there some kind of elegant way? There is no function in InetAddress for this.

  • Get the network IP from the input IP mask and subnet mask.

     mask = (long)(0xffffffff) << (32-subnetMask); Long netIp = getLongfromIp(Inputip)& mask;

The getLongfromIp function contains code from How to convert string (IP numbers) to Integer in Java

  1. get the number of hosts using a subnet mask

    maxRange = (long)0x1<<(32-subnetMask);

  2. Get the address of all hopes by adding I for i in (0 .. maxRange) in netIp

  3. Convert ip from step above to octet string.

Ps: I am sure that IP addresses will only be in IPV4.

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4 answers

Answering my question, the solution is to use the Apache commons.net library

 import org.apache.commons.net.util.*; SubnetUtils utils = new SubnetUtils("192.168.1.0/24"); String[] allIps = utils.getInfo().getAllAddresses(); //appIps will contain all the ip address in the subnet

Read more: SubnetUtils.SubnetInfo Class

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To enable NetworkAddress and BroadcastAddress

 import org.apache.commons.net.util.*; SubnetUtils utils = new SubnetUtils("192.168.1.0/28"); utils.setInclusiveHostCount(true); String[] allIps = utils.getInfo().getAllAddresses();
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IPAddress Java Library supports both IPv4 and IPv6 subnets in a polymorphic fashion. Disclaimer: I am a project manager.

Here is sample code for transparently displaying an address list for an IPv4 or IPv6 subnet. Subnets can be quite large, especially with IPv6, and you should not try to iterate over a large subnet, so the code for iterateEdges shows how to iterate over only the start and end addresses in the subnet.

 show("192.168.10.0/24"); show("2001:db8:abcd:0012::/64"); static void show(String subnet) throws AddressStringException { IPAddressString addrString = new IPAddressString(subnet); IPAddress addr = addrString.toAddress(); show(addr); } static void show(IPAddress subnet) { Integer prefixLength = subnet.getNetworkPrefixLength(); if(prefixLength == null) { prefixLength = subnet.getBitCount(); } IPAddress mask = subnet.getNetwork().getNetworkMask(prefixLength, false); BigInteger count = subnet.getCount(); System.out.println("Subnet of size " + count + " with prefix length " + prefixLength + " and mask " + mask); System.out.println("Subnet ranges from " + subnet.getLower() + " to " + subnet.getUpper()); int edgeCount = 3; if(count.compareTo(BigInteger.valueOf(256)) <= 0) { iterateAll(subnet, edgeCount); } else { iterateEdges(subnet, edgeCount); } }

Iterates over the entire subnet, use with caution:

 static void iterateAll(IPAddress subnet, int edgeCount) { BigInteger count = subnet.getCount(); BigInteger bigEdge = BigInteger.valueOf(edgeCount), currentCount = count; int i = 0; for(IPAddress addr: subnet.getIterable()) { currentCount = currentCount.subtract(BigInteger.ONE); if(i < edgeCount) { System.out.println(++i + ": " + addr); } else if(currentCount.compareTo(bigEdge) < 0) { System.out.println(count.subtract(currentCount) + ": " + addr); } else if(i == edgeCount) { System.out.println("...skipping..."); i++; } } }

Iterate over the edges of the subnet:

 static void iterateEdges(IPAddress subnet, int edgeCount) { for(int increment = 0; increment < edgeCount; increment++) { System.out.println((increment + 1) + ": " + subnet.getLower().increment(increment)); } System.out.println("...skipping..."); BigInteger count = subnet.getCount(); for(int decrement = 1 - edgeCount; decrement <= 0; decrement++) { System.out.println(count.add(BigInteger.valueOf(decrement)) + ": " + subnet.getUpper().increment(decrement)); } }

Here is the conclusion:

 Subnet of size 256 with prefix length 24 and mask 255.255.255.0 Subnet ranges from 192.168.5.0/24 to 192.168.5.255/24 1: 192.168.5.0/24 2: 192.168.5.1/24 3: 192.168.5.2/24 ...skipping... 254: 192.168.5.253/24 255: 192.168.5.254/24 256: 192.168.5.255/24 Subnet of size 18446744073709551616 with prefix length 64 and mask ffff:ffff:ffff:ffff:: Subnet ranges from 2001:db8:abcd:12::/64 to 2001:db8:abcd:12:ffff:ffff:ffff:ffff/64 1: 2001:db8:abcd:12::/64 2: 2001:db8:abcd:12::1/64 3: 2001:db8:abcd:12::2/64 ...skipping... 18446744073709551614: 2001:db8:abcd:12:ffff:ffff:ffff:fffd/64 18446744073709551615: 2001:db8:abcd:12:ffff:ffff:ffff:fffe/64 18446744073709551616: 2001:db8:abcd:12:ffff:ffff:ffff:ffff/64
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The following answer is similar to Sean's answer (very nice!) Using https://seancfoley.imtqy.com/IPAddress/ , it only reduces the signal-to-noise ratio:

 subnetToIps("192.168.10.0/28"); public void subnetToIps(String ipOrCidr) { IPAddressString addrString = new IPAddressString(ipOrCidr, IPAddressString.DEFAULT_VALIDATION_OPTIONS); IPAddress subnet = addrString.toAddress(); System.out.println("Subnet ranges from " + subnet.getLower() + " to " + subnet.getUpper()); int i = 0; for (IPAddress addr : subnet.getIterable()) { System.out.println(++i + ": " + addr); } }
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Source: https://habr.com/ru/post/1206175/

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