diff --git a/server/src/com/cloud/network/vpn/Site2SiteVpnManagerImpl.java b/server/src/com/cloud/network/vpn/Site2SiteVpnManagerImpl.java
index e0d2c877fbb..4f7277256a4 100644
--- a/server/src/com/cloud/network/vpn/Site2SiteVpnManagerImpl.java
+++ b/server/src/com/cloud/network/vpn/Site2SiteVpnManagerImpl.java
@@ -217,6 +217,18 @@ public class Site2SiteVpnManagerImpl implements Site2SiteVpnManager, Manager {
             throw new InvalidParameterValueException("The vpn connection with specified customer gateway id " +
                     " already exists!", idList);
         }
+
+        String[] cidrList = customerGateway.getGuestCidrList().split(",");
+        String vpcCidr = _vpcDao.findById(vpnGateway.getVpcId()).getCidr();
+        for (String cidr : cidrList) {
+            if (NetUtils.isNetworksOverlap(vpcCidr, cidr)) {
+                List<IdentityProxy> idList = new ArrayList<IdentityProxy>();
+                idList.add(new IdentityProxy(customerGateway, customerGatewayId, "customerGatewayId"));
+                throw new InvalidParameterValueException("The subnet of customer gateway " + cidr + " is overlapped with VPC cidr " +
+                        vpcCidr + "!", idList);
+            }
+        }
+
         Site2SiteVpnConnectionVO conn = new Site2SiteVpnConnectionVO(owner.getAccountId(), owner.getDomainId(), vpnGatewayId, customerGatewayId);
         conn.setState(State.Pending);
         _vpnConnectionDao.persist(conn);