NetCalc

Advanced network calculator and address planning helper.

NetCalc is a tool made by network admins, for network admins. It supports adding (aggregating) networks, subtracting a network from a larger network, doing addition and subtraction of multiple networks at once, and more functionality is to come in future releases.

NetCalc supports both IPv4 and IPv6, and works very efficiently even with very large networks. It uses the excellent netaddr library for the core address manipulation.

This program requires either Python 3 (recommended) or Python 2.

Usage

Using NetCalc is quite simple. All functionality is split into commands, each of which receive their own set of specific arguments.

add command

Add networks, aggregating as much as possible.

$ netcalc add 198.18.0.0/24 198.18.1.0/24 10.1/16 10/16
10.0.0.0/15
198.18.0.0/23

This command can be very useful e.g. for calculating a minimal set of prefixes to announce with BGP.

Another real-life example would be comparing the routing tables from two separate routers (each with prefixes broken up in different ways), to see if they are equivalent (both cover the same networks). If the aggregate from one router matches the aggregate from the other, then they are indeed equivalent.

add-file command

Add networks from a file, aggregating as much as possible.

This is a variant of the add command above, which reads the networks from a file (one per line). For example, given the following file:

networks.txt

198.18.0.0/24
198.18.1.0/24
10.1/16
10/16

These networks could be added like so:

$ netcalc add-file networks.txt
10.0.0.0/15
198.18.0.0/23

sub command

Subtract a network from another, splitting as necessary.

$ netcalc sub 192.0.2.0/24 192.0.2.0/28
192.0.2.16/28
192.0.2.32/27
192.0.2.64/26
192.0.2.128/25

split command

Split a network into subnets of a certain length.

$ netcalc split 198.18.64.0/18 20
198.18.64.0/20
198.18.80.0/20
198.18.96.0/20
198.18.112.0/20

It is also possible to do a hierarchical split, showing all the steps from a certain length to a specified maximum length:

$ netcalc split 198.18.64.0/18 19 21
198.18.64.0/19
  198.18.64.0/20
    198.18.64.0/21
    198.18.72.0/21
  198.18.80.0/20
    198.18.80.0/21
    198.18.88.0/21
198.18.96.0/19
  198.18.96.0/20
    198.18.96.0/21
    198.18.104.0/21
  198.18.112.0/20
    198.18.112.0/21
    198.18.120.0/21

expr command

Add and subtract networks using an arbitrarily long mathematical expression.

$ netcalc expr 2001:db8::/34 - 2001:db8::/38 + 2001:db8:100::/41
2001:db8:100::/41
2001:db8:400::/38
2001:db8:800::/37
2001:db8:1000::/36
2001:db8:2000::/35

info command

Provide static information about a network. Shows the network address, netmask, first and last addresses, and so on.

$ netcalc info 2001:db8::8000:0:0:a:5/56
Compact address   - 2001:db8:0:8000::a:5
Expanded address  - 2001:0db8:0000:8000:0000:0000:000a:0005
Address type      - Global Unicast
Network address   - 2001:db8:0:8000::/56
Network mask      - ffff:ffff:ffff:ff00:0:0:0:0
Prefix length     - 56
Host wildcard     - 0:0:0:ff:ffff:ffff:ffff:ffff
Broadcast address - N/A
Address count     - 4722366482869645213696
First address     - 2001:0db8:0000:8000:0000:0000:0000:0000
Last address      - 2001:0db8:0000:80ff:ffff:ffff:ffff:ffff

Expanding arguments from a text file

It is possible to expand command-line arguments from a text file, for any command, by referencing the filename with a @ placeholder. The file's contents will be read and inserted as though they had been typed at the command-line. Each line of text will turn into a separate command line argument.

Argument expansion is useful for commands which don't already support receiving a filename from which to read their arguments. Using this, it is possible for example to calculate an arbitrarily long expression with the expr command.

For example, given the following file:

/tmp/math-arguments.txt

2001:db8::/34
-
2001:db8::/38
+
2001:db8:100::/41

This expression could be calculated like so:

$ netcalc expr @/tmp/math-arguments.txt
2001:db8:100::/41
2001:db8:400::/38
2001:db8:800::/37
2001:db8:1000::/36
2001:db8:2000::/35

It is even possible (albeit perhaps farfetched) to specify the actual command within the argument file:

/tmp/arguments.txt

sub
10.0.0.0/24
10.0.0.64/27

Which would yield:

$ netcalc @arguments.txt
10.0.0.0/26
10.0.0.96/27
10.0.0.128/25

Of course, it would also be possible to use argument expansion to read networks from a file as arguments into the add command. However, this would be rather redundant, as it is equivalent to just using the add-file command, exemplified above.

Given the file:

networks.txt

198.18.0.0/24
198.18.1.0/24
10.1/16
10/16

These networks could be added like so:

$ netcalc add @networks.txt
10.0.0.0/15
198.18.0.0/23

Installing

Using pip

The easiest, portable, way to install NetCalc is through the official Python Package Index, using a package manager such as pip:

$ sudo pip install netcalc

This will install NetCalc globally, and take care of installing all necessary dependencies first.

It is also possible to install only to the local user's environment, without changing the global system:

$ pip install --user netcalc

This will install NetCalc in the user's environment, which can be e.g. in ~/.local in GNU/Linux, UNIX and Mac OSX, or %APPDATA%\Python in Windows. You will need to run netcalc from within the user environment: on GNU/Linux for example, this will be ~/.local/bin/netcalc.

From the operating system's package manager

There are packages available for Debian Jessie (.deb), which should also work for Ubuntu Linux:

• python-netcalc (for Python 2)
• python3-netcalc (for Python 3)

A package for Gentoo Linux (ebuild) is also planned for future releases.

From source

NetCalc can also be run directly from the source directory, as long as the requirements are already installed.

The only requirement is netaddr. On a Debian or Ubuntu system, install the python3-netaddr package (for Python 3), or python-netaddr (for Python 2). On a Gentoo system, install dev-python/netaddr.

To run from source, just execute ./netcalc.py from within the root of the source directory:

$ cd netcalc
$ ./netcalc.py add 10.0.0.24/29 10.0.0.16/29
10.0.0.16/28

Future plans

Future plans for NetCalc include, in no particular order:

• new command for static information (netmask/bitmask, IP range)
• new command for WHOIS queries
• make expr command more generic, allow e.g. splitting subnets
• ability to read networks from file in different formats (CSV, etc.)
• create packages for common GNU/Linux distributions, and installer for Windows
• ???

Suggestions are quite welcome :)

Contact

NetCalc is developed by Israel G. Lugo <[email protected]>. Main repository for cloning, submitting issues and/or forking is at https://github.com/israel-lugo/netcalc

License

Copyright (C) 2016, 2017 Israel G. Lugo <[email protected]>

NetCalc is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

NetCalc is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with NetCalc. If not, see <http://www.gnu.org/licenses/>.