I have written a IP calcultor for personal use. Yes, there is a command line version the great, web based ipcalc. I only recently discovered that and been using it since. That probably only delayed writing my own.
Why would you want to reinvent ipcalc, you may ask. Because there are few little features I need.
First, when I get a big CIDR and have to split it up into subnets, perhaps of uneven size, I want to to know the start of the next possible subnet.
I also want to know if a given IP is within a given CIDR range. And in the same spirit, I want check for posisble CIDR overlaps.
I had implemented all these capabilities, previously in a different (private) tool (In Go). Hence I knew it only takes a little effort. Also, with net/netip, overlaps checks are built in!
And here goes ipeter
Naming is hard. I just named it after a colleague who I go to when I want some IPs I can safely use in my $dayjob.
Let me show you it’s features
> ipeter calc 10.1.0.0/28
Network: 10.1.0.0/28 (Class A)
Netmask: 255.255.255.240
Broadcast: 10.1.0.15
Hosts/Net: 14
Next: 10.1.0.16
As you can see, calc is inspired by ipcalc. Plus it shows the next IP.
> ipeter cidr 10.0.1.0/24 overlaps 10.0.0.0/24
false
> ipeter cidr 10.0.1.0/24 overlaps 10.0.0.0/8
true
I went a little experimental with the interface for this, using the positional aruments branching featue in alecthomas/kong.
Kong has been my favorite go cli library for a while now. The ease of use and the features feel just right for me!
Next up, I also did the check for ip being within a CIDR in the same style as above.
> ipeter ip 10.0.0.36 in 10.0.0.0/27
false
> ipeter ip 10.0.0.1 in 10.0.0.0/27
true
However, to check multiple IPs at once, there’s also
> ipeter contains 100.64.0.0/10 192.168.10.1 10.1.0.0 100.100.1.1
192.168.10.1 : false
10.1.0.0 : false
100.100.1.1 : true
And las but not least, quickly find out the netmasks that can house a given number of hosts
> ipeter mask 345 34
netmask for 345 hosts is /23
netmask for 34 hosts is /26
Turns out I can do whatever I want when the intended audience is just one and it’s just me! Don’t use this software. Or do use. Do whatever you want.
Asides:
A IP calulator? Yes!
“Let me show you it’s features” is a phrase commonly used by Joerg Sprave at the slingshot channel.