Sometimes you need to know if a certain IP (or several ones) are within an IP range or belong to a certain ASN. Let’s give it a try and generate all possible IP addresses for telekom.de.

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$ dig telekom.de 
...
telekom.de.     86346   IN  A   46.29.100.76
...

Now let’s find out the ASN:

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$ whois 46.29.100.76 | grep origin            
origin:         AS34086

Now ask RIPE for the IP ranges:

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$ whois -h whois.ripe.net -T route AS34086 -i origin | egrep "route: " | awk '{print $NF}'   
145.225.1.0/24
151.136.0.0/16
185.9.216.0/22
193.143.55.0/24
193.143.56.0/24
193.143.57.0/24
217.150.144.0/20
217.150.144.0/21
46.29.96.0/21
93.188.240.0/21
94.100.240.0/20

Now for every IP range let’s generate all possible IP addresses. Therefore I’ve wrote a simple python script.

I know there is cidr2range but that didn’t work for certain blocks like 145.225.1.0/24.

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$ cat cidr2list.py 
#!/usr/bin/env python2

import sys
from netaddr import IPNetwork

if __name__ == "__main__":
    if len(sys.argv) != 2:
        print "Usage: %s <CIDR Block>\n" % sys.argv[0]
    else:
        for ip in IPNetwork(sys.argv[1]):
            print '%s' % ip

Now let’s generate the lists:

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$ whois -h whois.ripe.net -T route AS34086 -i origin | egrep "route: " | awk '{print $NF}'  >> /tmp/ip-ranges.txt
$ cat /tmp/ip-ranges.txt | xargs -n1 ./cidr2list.py > /tmp/ip-lists.txt
$  head -n 10 /tmp/ip-lists.txt 
145.225.1.0
145.225.1.1
145.225.1.2
145.225.1.3
145.225.1.4
145.225.1.5
145.225.1.6
145.225.1.7
145.225.1.8
145.225.1.9
$ wc -l /tmp/ip-lists.txt 
81920 /tmp/ip-lists.txt

Voila! :)