diff --git a/corefx/src/main/java/com/core/data/NodeType.java b/corefx/src/main/java/com/core/data/NodeType.java
index 4af7dc3d..3b070799 100644
--- a/corefx/src/main/java/com/core/data/NodeType.java
+++ b/corefx/src/main/java/com/core/data/NodeType.java
@@ -73,11 +73,9 @@ public class NodeType {
         return ID_LOOKUP.values().stream()
                 .filter(nodeType -> {
                     boolean sameType = nodeType.getValue() == type;
-                    boolean sameModel;
-                    if (model != null) {
+                    boolean sameModel = true;
+                    if (!model.isEmpty()) {
                         sameModel = model.equals(nodeType.getModel());
-                    } else {
-                        sameModel = nodeType.getModel() == null;
                     }
                     return sameType && sameModel;
                 })
diff --git a/corefx/src/main/java/com/core/graph/CoreAddresses.java b/corefx/src/main/java/com/core/graph/CoreAddresses.java
index fdd872c4..70ab5e06 100644
--- a/corefx/src/main/java/com/core/graph/CoreAddresses.java
+++ b/corefx/src/main/java/com/core/graph/CoreAddresses.java
@@ -6,7 +6,9 @@ import inet.ipaddr.IPAddressString;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
+import java.beans.IndexedPropertyDescriptor;
 import java.util.Comparator;
+import java.util.HashSet;
 import java.util.Queue;
 import java.util.Set;
 import java.util.concurrent.ArrayBlockingQueue;
@@ -16,8 +18,14 @@ import java.util.concurrent.atomic.AtomicBoolean;
 public class CoreAddresses {
     private static final Logger logger = LogManager.getLogger();
     private IPAddress currentSubnet = new IPAddressString("10.0.0.0/24").getAddress().toPrefixBlock();
-    private AtomicBoolean firstSubnet = new AtomicBoolean(true);
     private Queue<IPAddress> deleted = new LinkedBlockingQueue<>();
+    private Set<IPAddress> usedSubnets = new HashSet<>();
+
+    public void usedAddress(IPAddress address) {
+        logger.info("adding used address: {} - {}", address, address.toPrefixBlock());
+        usedSubnets.add(address.toPrefixBlock());
+        logger.info("used subnets: {}", usedSubnets);
+    }
 
     public void reuseSubnet(IPAddress subnet) {
         deleted.add(subnet);
@@ -25,16 +33,18 @@ public class CoreAddresses {
 
     public IPAddress nextSubnet() {
         logger.info("getting next subnet: {}", currentSubnet);
-        if (!firstSubnet.getAndSet(false)) {
-            IPAddress deletedSubnet = deleted.poll();
-            if (deletedSubnet != null) {
-                currentSubnet = deletedSubnet;
-            } else {
-                currentSubnet = currentSubnet.incrementBoundary(1).toPrefixBlock();
-            }
+        // skip existing subnets, when loaded from file
+        while (usedSubnets.contains(currentSubnet)) {
+            currentSubnet = currentSubnet.incrementBoundary(1).toPrefixBlock();
         }
-        logger.info("getting updated boundary: {}", currentSubnet);
-        return currentSubnet;
+
+        // re-use any deleted subnets
+        IPAddress next = deleted.poll();
+        if (next == null) {
+            next = currentSubnet;
+            currentSubnet = currentSubnet.incrementBoundary(1).toPrefixBlock();
+        }
+        return next;
     }
 
     public IPAddress findSubnet(Set<CoreInterface> interfaces) {
@@ -58,7 +68,7 @@ public class CoreAddresses {
 
     public void reset() {
         deleted.clear();
-        firstSubnet.set(true);
+        usedSubnets.clear();
         currentSubnet = new IPAddressString("10.0.0.0/24").getAddress().toPrefixBlock();
     }
 
diff --git a/corefx/src/main/java/com/core/graph/NetworkGraph.java b/corefx/src/main/java/com/core/graph/NetworkGraph.java
index 8dfe4e84..da3389ef 100644
--- a/corefx/src/main/java/com/core/graph/NetworkGraph.java
+++ b/corefx/src/main/java/com/core/graph/NetworkGraph.java
@@ -286,6 +286,13 @@ public class NetworkGraph {
     private void handleEdgeAdded(GraphEvent.Edge<CoreNode, CoreLink> edgeEvent) {
         CoreLink link = edgeEvent.getEdge();
         if (link.isLoaded()) {
+            // load addresses to avoid duplication
+            if (link.getInterfaceOne().getIp4() != null) {
+                coreAddresses.usedAddress(link.getInterfaceOne().getIp4());
+            }
+            if (link.getInterfaceTwo().getIp4() != null) {
+                coreAddresses.usedAddress(link.getInterfaceTwo().getIp4());
+            }
             return;
         }
         Pair<CoreNode> endpoints = graph.getEndpoints(link);
@@ -508,7 +515,7 @@ public class NetworkGraph {
     }
 
     private boolean isWirelessNode(CoreNode node) {
-        return node.getType() == NodeType.EMANE || node.getType() == NodeType.WLAN;
+        return node != null && (node.getType() == NodeType.EMANE || node.getType() == NodeType.WLAN);
     }
 
     private boolean checkForWirelessNode(CoreNode nodeOne, CoreNode nodeTwo) {
diff --git a/daemon/core/api/grpc/server.py b/daemon/core/api/grpc/server.py
index 72e390ff..b2c26f42 100644
--- a/daemon/core/api/grpc/server.py
+++ b/daemon/core/api/grpc/server.py
@@ -17,6 +17,7 @@ from core.emulator.emudata import NodeOptions, InterfaceData, LinkOptions
 from core.emulator.enumerations import NodeTypes, EventTypes, LinkTypes
 from core.location.mobility import BasicRangeModel, Ns2ScriptedMobility
 from core.nodes import nodeutils
+from core.nodes.base import CoreNetworkBase
 from core.nodes.ipaddress import MacAddress
 from core.services.coreservices import ServiceManager
 
@@ -73,18 +74,24 @@ def convert_link(session, link_data):
     interface_one = None
     if link_data.interface1_id is not None:
         node = session.get_node(link_data.node1_id)
-        interface = node.netif(link_data.interface1_id)
+        interface_name = None
+        if not isinstance(node, CoreNetworkBase):
+            interface = node.netif(link_data.interface1_id)
+            interface_name = interface.name
         interface_one = core_pb2.Interface(
-            id=link_data.interface1_id, name=interface.name, mac=convert_value(link_data.interface1_mac),
+            id=link_data.interface1_id, name=interface_name, mac=convert_value(link_data.interface1_mac),
             ip4=convert_value(link_data.interface1_ip4), ip4mask=link_data.interface1_ip4_mask,
             ip6=convert_value(link_data.interface1_ip6), ip6mask=link_data.interface1_ip6_mask)
 
     interface_two = None
     if link_data.interface2_id is not None:
         node = session.get_node(link_data.node2_id)
-        interface = node.netif(link_data.interface2_id)
+        interface_name = None
+        if not isinstance(node, CoreNetworkBase):
+            interface = node.netif(link_data.interface2_id)
+            interface_name = interface.name
         interface_two = core_pb2.Interface(
-            id=link_data.interface2_id, name=interface.name, mac=convert_value(link_data.interface2_mac),
+            id=link_data.interface2_id, name=interface_name, mac=convert_value(link_data.interface2_mac),
             ip4=convert_value(link_data.interface2_ip4), ip4mask=link_data.interface2_ip4_mask,
             ip6=convert_value(link_data.interface2_ip6), ip6mask=link_data.interface2_ip6_mask)