IPv4 Netzberechner

Ein Python-Skript für die Berechnung der Netze von IPv4-Adressen.

Code

#!/bin/env python3
import math
import sys

def cidr2mask(cidr_nr):
    """Convert the CIDR notation to a subnet mask and return a string
    representation of it.
    """
#Calculate full octetts
#    octett = math.floor(cidr_nr / 8)
    octett = math.ceil(cidr_nr / 8)
#Calculate exponent from CIDR notation
    exp = (8 - (cidr_nr % 8)) % 8

#Fill octetts
    mask = "0.0.0.0.0"
    mask = mask.replace("0", "255", octett)

#Subtract 2 ** exponent from 256
    m = 256 - (2 ** exp)
    mask = mask.replace("0", str(m), 1)

    return mask[4:]


def ip_table(ip, cidr):
    """Solves the subnetting problem as presented on
    \"https://subnetipv4.com/\". Returns the answer as a dictionary.
    """
#calculate in which octett the network ID will change
    octett = math.floor(cidr / 8)
#calculate the increment by which the networks IDs are found in
    incr = 256 / (2 ** (cidr % 8))
#calculate the network ID and first usable ip adrress
    net_id = ip.copy()
    net_id[octett] = int(math.floor(net_id[octett] / incr) * incr)

    for i in range(octett+1, 4):
        net_id[i] = 0

    first = net_id.copy()
    first[-1] += 1
#calculate the ID of the next network
    next_net = net_id.copy()
    nx = next_net[octett] + incr

    if nx == 256:
        next_net[octett] = 0
        next_net[octett-1] = next_net[octett-1] + 1

    else:
        next_net[octett] = nx

    broadcast = net_id.copy()
    broadcast[octett] += int(incr - 1)
    broadcast[octett+1:] = [255 for i in broadcast[octett+1:]]

    last = broadcast.copy()
    last[-1] -= 1

    fields = ["Net ID", "First IP", "Last IP", "Broadcast", "Next ID"]
    
    return dict(zip(fields, [net_id, first, last, broadcast, next_net]))


if __name__ == '__main__':
    ip_cidr = sys.argv[1]
#    print(ip_cidr)
    ip_cidr = ip_cidr.split("/")
    ip = [int(i) for i in ip_cidr[0].split(".")]
    cidr = int(ip_cidr[1])

    ips = ip_table(ip, cidr)
    print(".".join([str(i) for i in ips["Net ID"]]) + "/" + str(ip_cidr[1]))

#    for i, j in ips.items():
#        print(i, ":", j)

Installation

Skript kopieren und ausführbar machen:

xclip -sel clip -o > calcipv4net
chmod +x calcipv4net

Benutzung

Komplette IPv4-Adresse als Argument angeben:

calcipv4net 10.28.38.48/18
#10.28.0.0/18