How to generate random IPv6 address using Python(or in Scapy)?

Question

In my test case, I need to send out NA with random IPv6 source address and fixed prefix. For example:

fixed prefix 2001::cafe:/64. The remainder of the address should be random.

How to achieve in Python or in Scapy?

Answer 1

import random   
M = 16**4
"2001:cafe:" + ":".join(("%x" % random.randint(0, M) for i in range(6)))

Answer 2

Not sure from the question which parts of the address you want to be random. I'm assuming the last 2 bytes.

Using the python netaddr library:

import random
from netaddr.ip import IPNetwork, IPAddress

random.seed()
ip_a = IPAddress('2001::cafe:0') + random.getrandbits(16)
ip_n = IPNetwork(ip_a)
ip_n.prefixlen = 64

print ip_a
print ip_n

Sample output:

2001::cafe:c935
2001::cafe:c935/64

The advantage over simple string formatting, is it would be easy to customize the starting address, random bit len. Also the netaddr classes have many useful attr, e.g. the broadcast address of the network.