diff --git a/kjg/IPv6/randomnet.py b/kjg/IPv6/randomnet.py
new file mode 100644
index 0000000..f0c1326
--- /dev/null
+++ b/kjg/IPv6/randomnet.py
@@ -0,0 +1,52 @@
+from sys import argv
+import argparse
+import ipaddress
+import random
+#import getopt #option function
+
+parser = argparse.ArgumentParser(description="Generating IPv6 networks")
+parser.add_argument('--size', help="size")
+parser.add_argument('string', nargs='+', help="network")
+
+try:
+    args = parser.parse_args()
+    
+    if argv[1] == '--size':
+        ipnet = argv[3]
+        size = 128 - int(argv[2])
+    else:
+        if len(argv) > 2 :
+            ipnet = argv[1]
+            size = 128 - int(argv[2])
+        else:
+            ipnet = argv[1]
+            size = 80
+
+    ip = ipnet.split('/')
+    ip2 = ipaddress.ip_network(ip[0]).supernet(new_prefix=int(ip[1]))
+
+    # minimum network
+    minNet = ipaddress.ip_network(ip[0]).supernet(new_prefix=128-size)
+
+    # seperate network
+    ip2first = ipaddress.IPv6Network(ip2)[0]
+    ip2last = ipaddress.IPv6Network(ip2)[-1]
+    minNetlast = ipaddress.IPv6Network(minNet)[-1]
+
+    # calculation network
+    maxRan = int(ip2last) - int(minNetlast) >> size
+    result = ipaddress.ip_address((random.randrange(0,maxRan) << size) + int(ip2first)  )
+    resultNetwork = ipaddress.ip_network(result).supernet(new_prefix=128-size)
+
+    print(resultNetwork)
+    
+except:
+    info="""
+wrong input  
+ex) --size 64 2001:db8::/40 
+    or 2001:db8::/40 64
+    or 2001:db8::/40  #default size 48
+"""
+    print(info)
+
+