diff --git a/server/src/com/cloud/configuration/ConfigurationManager.java b/server/src/com/cloud/configuration/ConfigurationManager.java
index c5222dadf78..2e9bffd597d 100644
--- a/server/src/com/cloud/configuration/ConfigurationManager.java
+++ b/server/src/com/cloud/configuration/ConfigurationManager.java
@@ -214,5 +214,9 @@ public interface ConfigurationManager extends ConfigurationService, Manager {
      * @throws  
      */
     Pod editPod(long id, String name, String startIp, String endIp, String gateway, String netmask, String allocationStateStr);
+
+    void checkPodCidrSubnets(long zoneId, Long podIdToBeSkipped, String cidr);
+
+    void checkCidrVlanOverlap(long zoneId, String cidr);
     
 }
diff --git a/server/src/com/cloud/configuration/ConfigurationManagerImpl.java b/server/src/com/cloud/configuration/ConfigurationManagerImpl.java
index 0c19b9b89f1..933053162d2 100755
--- a/server/src/com/cloud/configuration/ConfigurationManagerImpl.java
+++ b/server/src/com/cloud/configuration/ConfigurationManagerImpl.java
@@ -636,7 +636,25 @@ public class ConfigurationManagerImpl implements ConfigurationManager, Configura
             }
         }
     }
+    
+    @Override
+    public void checkCidrVlanOverlap(long zoneId, String cidr) {
+            // Prevent using the same CIDR for POD and virtual networking
+            List<VlanVO> vlans = _vlanDao.listByZoneAndType(zoneId, VlanType.VirtualNetwork);
+            for (VlanVO vlan : vlans) {
+                String vlanCidr = NetUtils.ipAndNetMaskToCidr(vlan.getVlanGateway(), vlan.getVlanNetmask());
+                String[] cidrPairVlan = vlanCidr.split("\\/");
+                String[] vlanIpRange = NetUtils.getIpRangeFromCidr(cidrPairVlan[0], Long.valueOf(cidrPairVlan[1]));
 
+                String[] cidrPairPod = cidr.split("\\/");
+                String[] podIpRange = NetUtils.getIpRangeFromCidr(cidrPairPod[0], Long.valueOf(cidrPairPod[1]));
+
+                if (NetUtils.ipRangesOverlap(vlanIpRange[0], vlanIpRange[1], podIpRange[0], podIpRange[1])) {
+                    throw new InvalidParameterValueException("Pod's cidr conflicts with cidr of virtual network in zone id=" + zoneId);
+                }
+            }
+    }
+    
     private void checkPodAttributes(long podId, String podName, long zoneId, String gateway, String cidr, String startIp, String endIp, String allocationStateStr, boolean checkForDuplicates,
             boolean skipGatewayOverlapCheck) {
         if (checkForDuplicates) {
@@ -684,28 +702,8 @@ public class ConfigurationManagerImpl implements ConfigurationManager, Configura
 
         String checkPodCIDRs = _configDao.getValue("check.pod.cidrs");
         if (checkPodCIDRs == null || checkPodCIDRs.trim().isEmpty() || Boolean.parseBoolean(checkPodCIDRs)) {
-            // Check if the CIDR conflicts with the Guest Network or other pods
-            HashMap<Long, List<Object>> currentPodCidrSubnets = _podDao.getCurrentPodCidrSubnets(zoneId, podId);
-            List<Object> newCidrPair = new ArrayList<Object>();
-            newCidrPair.add(0, cidrAddress);
-            newCidrPair.add(1, new Long(cidrSize));
-            currentPodCidrSubnets.put(new Long(-1), newCidrPair);
-            checkPodCidrSubnets(zoneId, currentPodCidrSubnets);
-
-            // Prevent using the same CIDR for POD and virtual networking
-            List<VlanVO> vlans = _vlanDao.listByZoneAndType(zoneId, VlanType.VirtualNetwork);
-            for (VlanVO vlan : vlans) {
-                String vlanCidr = NetUtils.ipAndNetMaskToCidr(vlan.getVlanGateway(), vlan.getVlanNetmask());
-                String[] cidrPairVlan = vlanCidr.split("\\/");
-                String[] vlanIpRange = NetUtils.getIpRangeFromCidr(cidrPairVlan[0], Long.valueOf(cidrPairVlan[1]));
-
-                String[] cidrPairPod = cidr.split("\\/");
-                String[] podIpRange = NetUtils.getIpRangeFromCidr(cidrPairPod[0], Long.valueOf(cidrPairPod[1]));
-
-                if (NetUtils.ipRangesOverlap(vlanIpRange[0], vlanIpRange[1], podIpRange[0], podIpRange[1])) {
-                    throw new InvalidParameterValueException("Pod's cidr conflicts with cidr of virtual network in zone id=" + zoneId);
-                }
-            }
+            checkPodCidrSubnets(zoneId, podId, cidr);
+            checkCidrVlanOverlap(zoneId, cidr);
         }
 
         Grouping.AllocationState allocationState = null;
@@ -2692,16 +2690,25 @@ public class ConfigurationManagerImpl implements ConfigurationManager, Configura
         return pod.getCidrSize();
     }
 
-    private void checkPodCidrSubnets(long dcId, HashMap<Long, List<Object>> currentPodCidrSubnets) {
+    @Override
+    public void checkPodCidrSubnets(long dcId, Long podIdToBeSkipped, String cidr) {
         // For each pod, return an error if any of the following is true:
-        // 1. The pod's CIDR subnet conflicts with the guest network subnet
-        // 2. The pod's CIDR subnet conflicts with the CIDR subnet of any other
-        // pod
+        // The pod's CIDR subnet conflicts with the CIDR subnet of any other pod
         
-        // Iterate through all pods in this zone
+        // Check if the CIDR conflicts with the Guest Network or other pods
+        long skipPod = 0;
+        if (podIdToBeSkipped != null) {
+            skipPod = podIdToBeSkipped;
+        }
+        HashMap<Long, List<Object>> currentPodCidrSubnets = _podDao.getCurrentPodCidrSubnets(dcId, skipPod);
+        List<Object> newCidrPair = new ArrayList<Object>();
+        newCidrPair.add(0, getCidrAddress(cidr));
+        newCidrPair.add(1, getCidrSize(cidr));
+        currentPodCidrSubnets.put(new Long(-1), newCidrPair);
         
         String zoneName = getZoneName(dcId);
         
+        // Iterate through all pods in this zone
         for (Long podId : currentPodCidrSubnets.keySet()) {
             String podName;
             if (podId.longValue() == -1) {
@@ -2719,8 +2726,6 @@ public class ConfigurationManagerImpl implements ConfigurationManager, Configura
 
             String cidrSubnet = NetUtils.getCidrSubNet(cidrAddress, cidrSizeToUse);
             
-            //TODO add checking for CIDR of guest network in this data center
-
             // Iterate through the rest of the pods
             for (Long otherPodId : currentPodCidrSubnets.keySet()) {
                 if (podId.equals(otherPodId)) {
diff --git a/server/src/com/cloud/network/NetworkManagerImpl.java b/server/src/com/cloud/network/NetworkManagerImpl.java
index 6701e6aaede..511ad1eaf0f 100755
--- a/server/src/com/cloud/network/NetworkManagerImpl.java
+++ b/server/src/com/cloud/network/NetworkManagerImpl.java
@@ -2006,7 +2006,52 @@ public class NetworkManagerImpl implements NetworkManager, NetworkService, Manag
             _nicDao.expunge(nic.getId());
         }
     }
+    
+    private String getCidrAddress(String cidr) {
+        String[] cidrPair = cidr.split("\\/");
+        return cidrPair[0];
+    }
 
+    private int getCidrSize(String cidr) {
+        String[] cidrPair = cidr.split("\\/");
+        return Integer.parseInt(cidrPair[1]);
+    }
+
+    public void checkVirtualNetworkCidrOverlap(Long zoneId, String cidr) {
+        if (zoneId == null) {
+            return;
+        }
+        List<NetworkVO> networks = _networksDao.listByZone((long)zoneId);
+        Map<Long, String> networkToCidr = new HashMap<Long, String>();
+        for (NetworkVO network : networks) {
+            if (network.getGuestType() != GuestType.Isolated) {
+                continue;
+            }
+            networkToCidr.put(network.getId(), network.getCidr());
+        }
+        if (networkToCidr == null || networkToCidr.isEmpty()) {
+            return;
+        }
+        
+        String currCidrAddress = getCidrAddress(cidr);
+        int currCidrSize = getCidrSize(cidr);
+        
+        for (long networkId : networkToCidr.keySet()) {
+            String ntwkCidr = networkToCidr.get(networkId);
+            String ntwkCidrAddress = getCidrAddress(ntwkCidr);
+            int ntwkCidrSize = getCidrSize(ntwkCidr);
+            
+            long cidrSizeToUse = currCidrSize < ntwkCidrSize ? currCidrSize : ntwkCidrSize;
+            
+            String ntwkCidrSubnet = NetUtils.getCidrSubNet(getCidrAddress(ntwkCidr), cidrSizeToUse);
+            String cidrSubnet = NetUtils.getCidrSubNet(currCidrAddress, cidrSizeToUse);
+            
+            if (cidrSubnet.equals(ntwkCidrSubnet)) {
+                throw new InvalidParameterValueException("Warning: The existing network " + networkId + " have conflict CIDR subnets with new network!");
+            }
+        }
+    }
+    
     @Override
     @DB
     @ActionEvent(eventType = EventTypes.EVENT_NETWORK_CREATE, eventDescription = "creating network")
@@ -2174,7 +2219,9 @@ public class NetworkManagerImpl implements NetworkManager, NetworkService, Manag
         if (cidr != null && networkOfferingIsConfiguredForExternalNetworking(networkOfferingId)) {
             throw new InvalidParameterValueException("Cannot specify CIDR when using network offering with external firewall!");
         }
-
+        
+        checkVirtualNetworkCidrOverlap(zoneId, cidr);
+        
         Transaction txn = Transaction.currentTxn();
         txn.start();