diff --git a/commands/prepare.py b/commands/prepare.py
index 74c4da110..e1f20068e 100644
--- a/commands/prepare.py
+++ b/commands/prepare.py
@@ -28,7 +28,7 @@
 import argparse
 import pyjq
 from netaddr import IPNetwork, IPAddress
-from shared.common import get_account, query_aws, get_regions
+from shared.common import get_account, query_aws, get_regions, is_external_cidr
 from shared.nodes import Account, Region, Vpc, Az, Subnet, Ec2, Elb, Rds, Cidr, Connection
 
 __description__ = "Generate network connection information file"
@@ -92,17 +92,6 @@ def get_sgs(vpc):
     return pyjq.all('.SecurityGroups[] | select(.VpcId == "{}")'.format(vpc.local_id), sgs)
 
 
-def is_external_cidr(cidr):
-    ipnetwork = IPNetwork(cidr)
-    if (
-            ipnetwork in IPNetwork("10.0.0.0/8") or
-            ipnetwork in IPNetwork("172.16.0.0/12") or
-            ipnetwork in IPNetwork("192.168.0.0/16")
-    ):
-        return False
-    return True
-
-
 def get_external_cidrs(account, config):
     external_cidrs = []
     unique_cidrs = {}
diff --git a/shared/common.py b/shared/common.py
index 6d3720164..d11d6b31c 100644
--- a/shared/common.py
+++ b/shared/common.py
@@ -5,6 +5,7 @@
 import datetime
 import pyjq
 import sys
+from netaddr import IPNetwork
 
 class Severity:
     DEBUG = 0
@@ -61,6 +62,8 @@ def log_issue(severity, msg, location=None, reasons=[]):
             'Reasons': reasons
         }
         print(json.dumps(json_issue, sort_keys=True), file=sys.stderr)
+
+
 def datetime_handler(x):
     if isinstance(x, datetime.datetime):
         return x.isoformat()
@@ -73,6 +76,17 @@ def make_list(v):
     return v
 
 
+def is_external_cidr(cidr):
+    ipnetwork = IPNetwork(cidr)
+    if (
+            ipnetwork in IPNetwork("10.0.0.0/8") or
+            ipnetwork in IPNetwork("172.16.0.0/12") or
+            ipnetwork in IPNetwork("192.168.0.0/16")
+    ):
+        return False
+    return True
+
+
 def query_aws(account, query, region=None):
     if not region:
         file_name = 'account-data/{}/{}.json'.format(account.name, query)