diff --git a/DHCPLease.cs b/DHCPLease.cs
index f8b52a7..aab5d9a 100644
--- a/DHCPLease.cs
+++ b/DHCPLease.cs
@@ -1,8 +1,11 @@
 using System;
 using ln.types.net;
 using ln.types.odb.attributes;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Converters;
 namespace ln.dhcp
 {
+    [JsonConverter(typeof(StringEnumConverter))]
     public enum DHCPLeaseState
     {
         RELEASED,
diff --git a/DHCPServer.cs b/DHCPServer.cs
index 7267796..8ffd8d2 100644
--- a/DHCPServer.cs
+++ b/DHCPServer.cs
@@ -288,6 +288,7 @@ namespace ln.dhcp
                         lease.ValidThrough = validThrough;
                     }
                     lease.LeaseState = DHCPLeaseState.BOUND;
+                    lease.LastUpdate = DateTimeOffset.Now;
                     Commit(lease);
                     logLease.Log(LogLevel.INFO, "[ACK    ] {0} {1} {2}", lease.ClientMAC, lease.ClientIP, lease.ClientName);
 
@@ -328,10 +329,11 @@ namespace ln.dhcp
                 IPv4 test = start;
                 while (leasesAPI.FindLease(test) != null)
                 {
-                    test = ippool.NextIP;
+                    test = ippool.GetNextIP();
                     if (test.Equals(start))
                         return null;
                 }
+                Commit(ippool);
                 return test;
             }
         }
diff --git a/IPPool.cs b/IPPool.cs
index fbae4ed..794ccaa 100644
--- a/IPPool.cs
+++ b/IPPool.cs
@@ -13,20 +13,24 @@ namespace ln.dhcp
         public IPv4 LastIP { get; set; }
 
         IPv4 nextIP;
-        public IPv4 NextIP 
+        public IPv4 NextIP
         {
-            get
+            get => nextIP;
+            set => nextIP = value;
+        }
+
+        public TimeSpan DefaultLeaseTime { get; set; }
+
+        public IPv4 GetNextIP()
+        {
+            lock (this)
             {
                 IPv4 next = nextIP++;
                 if (nextIP > LastIP)
                     nextIP = FirstIP;
                 return next;
             }
-            set => nextIP = value;
         }
-
-        public TimeSpan DefaultLeaseTime { get; set; }
-
         private IPPool()
         {
             DefaultLeaseTime = TimeSpan.FromHours(1);
diff --git a/bin/Debug/Newtonsoft.Json.dll b/bin/Debug/Newtonsoft.Json.dll
index d0aaed9..4395f61 100755
Binary files a/bin/Debug/Newtonsoft.Json.dll and b/bin/Debug/Newtonsoft.Json.dll differ
diff --git a/bin/Debug/Newtonsoft.Json.pdb b/bin/Debug/Newtonsoft.Json.pdb
deleted file mode 100755
index 0cfd893..0000000
Binary files a/bin/Debug/Newtonsoft.Json.pdb and /dev/null differ
diff --git a/bin/Debug/Newtonsoft.Json.xml b/bin/Debug/Newtonsoft.Json.xml
index b2810a0..9e42a41 100755
--- a/bin/Debug/Newtonsoft.Json.xml
+++ b/bin/Debug/Newtonsoft.Json.xml
@@ -1514,7 +1514,7 @@
             Converts the <see cref="T:System.Decimal"/> to its JSON string representation.
             </summary>
             <param name="value">The value to convert.</param>
-            <returns>A JSON string representation of the <see cref="T:System.SByte"/>.</returns>
+            <returns>A JSON string representation of the <see cref="T:System.Decimal"/>.</returns>
         </member>
         <member name="M:Newtonsoft.Json.JsonConvert.ToString(System.Guid)">
             <summary>
@@ -2162,6 +2162,12 @@
             </summary>
             <value>The member serialization.</value>
         </member>
+        <member name="P:Newtonsoft.Json.JsonObjectAttribute.MissingMemberHandling">
+            <summary>
+            Gets or sets the missing member handling used when deserializing this object.
+            </summary>
+            <value>The missing member handling.</value>
+        </member>
         <member name="P:Newtonsoft.Json.JsonObjectAttribute.ItemNullValueHandling">
             <summary>
             Gets or sets how the object's properties with null values are handled during serialization and deserialization.
@@ -8103,6 +8109,13 @@
             </summary>
             <param name="token">The token to read from.</param>
         </member>
+        <member name="M:Newtonsoft.Json.Linq.JTokenReader.#ctor(Newtonsoft.Json.Linq.JToken,System.String)">
+            <summary>
+            Initializes a new instance of the <see cref="T:Newtonsoft.Json.Linq.JTokenReader"/> class.
+            </summary>
+            <param name="token">The token to read from.</param>
+            <param name="initialPath">The initial path of the token. It is prepended to the returned <see cref="P:Newtonsoft.Json.Linq.JTokenReader.Path"/>.</param>
+        </member>
         <member name="M:Newtonsoft.Json.Linq.JTokenReader.Read">
             <summary>
             Reads the next JSON token from the underlying <see cref="T:Newtonsoft.Json.Linq.JToken"/>.
@@ -10199,6 +10212,13 @@
             </summary>
             <value>The converter.</value>
         </member>
+        <member name="P:Newtonsoft.Json.Serialization.JsonContract.InternalConverter">
+            <summary>
+            Gets the internally resolved <see cref="T:Newtonsoft.Json.JsonConverter"/> for the contract's type.
+            This converter is used as a fallback converter when no other converter is resolved.
+            Setting <see cref="P:Newtonsoft.Json.Serialization.JsonContract.Converter"/> will always override this converter.
+            </summary>
+        </member>
         <member name="P:Newtonsoft.Json.Serialization.JsonContract.OnDeserializedCallbacks">
             <summary>
             Gets or sets all methods called immediately after deserialization of the object.
@@ -10344,6 +10364,12 @@
             </summary>
             <value>The member object serialization.</value>
         </member>
+        <member name="P:Newtonsoft.Json.Serialization.JsonObjectContract.MissingMemberHandling">
+            <summary>
+            Gets or sets the missing member handling used when deserializing this object.
+            </summary>
+            <value>The missing member handling.</value>
+        </member>
         <member name="P:Newtonsoft.Json.Serialization.JsonObjectContract.ItemRequired">
             <summary>
             Gets or sets a value that indicates whether the object's properties are required.
@@ -10510,6 +10536,11 @@
             </summary>
             <value>A value indicating whether this <see cref="T:Newtonsoft.Json.Serialization.JsonProperty"/> is required.</value>
         </member>
+        <member name="P:Newtonsoft.Json.Serialization.JsonProperty.IsRequiredSpecified">
+            <summary>
+            Gets a value indicating whether <see cref="P:Newtonsoft.Json.Serialization.JsonProperty.Required"/> has a value specified.
+            </summary>
+        </member>
         <member name="P:Newtonsoft.Json.Serialization.JsonProperty.IsReference">
             <summary>
             Gets or sets a value indicating whether this property preserves object references.
@@ -10760,6 +10791,26 @@
             <param name="name">The property name to resolve.</param>
             <returns>The resolved property name.</returns>
         </member>
+        <member name="M:Newtonsoft.Json.Serialization.NamingStrategy.GetHashCode">
+            <summary>
+            Hash code calculation
+            </summary>
+            <returns></returns>
+        </member>
+        <member name="M:Newtonsoft.Json.Serialization.NamingStrategy.Equals(System.Object)">
+            <summary>
+            Object equality implementation
+            </summary>
+            <param name="obj"></param>
+            <returns></returns>
+        </member>
+        <member name="M:Newtonsoft.Json.Serialization.NamingStrategy.Equals(Newtonsoft.Json.Serialization.NamingStrategy)">
+            <summary>
+            Compare to another NamingStrategy
+            </summary>
+            <param name="other"></param>
+            <returns></returns>
+        </member>
         <member name="T:Newtonsoft.Json.Serialization.ObjectConstructor`1">
             <summary>
             Represents a method that constructs an object.
diff --git a/bin/Debug/ln.dhcp.dll b/bin/Debug/ln.dhcp.dll
index 3cb0a67..f212fae 100644
Binary files a/bin/Debug/ln.dhcp.dll and b/bin/Debug/ln.dhcp.dll differ
diff --git a/bin/Debug/ln.dhcp.pdb b/bin/Debug/ln.dhcp.pdb
index cda7738..1d5f917 100644
Binary files a/bin/Debug/ln.dhcp.pdb and b/bin/Debug/ln.dhcp.pdb differ
diff --git a/bin/Debug/ln.types.dll b/bin/Debug/ln.types.dll
index 650415c..a9fe7c0 100644
Binary files a/bin/Debug/ln.types.dll and b/bin/Debug/ln.types.dll differ
diff --git a/bin/Debug/sharp.logging.dll b/bin/Debug/sharp.logging.dll
index 3b6b9a5..0f2a906 100644
Binary files a/bin/Debug/sharp.logging.dll and b/bin/Debug/sharp.logging.dll differ
diff --git a/ln.dhcp.csproj b/ln.dhcp.csproj
index 87ee592..27895b4 100644
--- a/ln.dhcp.csproj
+++ b/ln.dhcp.csproj
@@ -29,6 +29,9 @@
   <ItemGroup>
     <Reference Include="System" />
     <Reference Include="Mono.Posix" />
+    <Reference Include="Newtonsoft.Json">
+      <HintPath>..\packages\Newtonsoft.Json.12.0.2\lib\net45\Newtonsoft.Json.dll</HintPath>
+    </Reference>
   </ItemGroup>
   <ItemGroup>
     <Compile Include="DHCPServer.cs" />
@@ -51,5 +54,8 @@
       <Name>ln.logging</Name>
     </ProjectReference>
   </ItemGroup>
+  <ItemGroup>
+    <None Include="packages.config" />
+  </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
 </Project>
\ No newline at end of file
diff --git a/obj/Debug/ln.dhcp.csproj.CoreCompileInputs.cache b/obj/Debug/ln.dhcp.csproj.CoreCompileInputs.cache
index a039c52..c1d016e 100644
--- a/obj/Debug/ln.dhcp.csproj.CoreCompileInputs.cache
+++ b/obj/Debug/ln.dhcp.csproj.CoreCompileInputs.cache
@@ -1 +1 @@
-62f8061fbf7e671ceaa150fc217748d6af510370
+52f74c261979b87de87fda0ff386127bee4e9aa4
diff --git a/obj/Debug/ln.dhcp.csproj.FileListAbsolute.txt b/obj/Debug/ln.dhcp.csproj.FileListAbsolute.txt
index 66a348f..979c095 100644
--- a/obj/Debug/ln.dhcp.csproj.FileListAbsolute.txt
+++ b/obj/Debug/ln.dhcp.csproj.FileListAbsolute.txt
@@ -25,4 +25,3 @@
 /home/haraldwolff/src/ln.skyspot/ln.dhcp/bin/Debug/sharp.logging.pdb
 /home/haraldwolff/src/ln.skyspot/ln.dhcp/bin/Debug/Newtonsoft.Json.xml
 /home/haraldwolff/src/ln.skyspot/ln.dhcp/obj/Debug/ln.dhcp.csproj.CopyComplete
-/home/haraldwolff/src/ln.skyspot/ln.dhcp/bin/Debug/Newtonsoft.Json.pdb
diff --git a/obj/Debug/ln.dhcp.csprojAssemblyReference.cache b/obj/Debug/ln.dhcp.csprojAssemblyReference.cache
index 31d7b7e..8e98121 100644
Binary files a/obj/Debug/ln.dhcp.csprojAssemblyReference.cache and b/obj/Debug/ln.dhcp.csprojAssemblyReference.cache differ
diff --git a/obj/Debug/ln.dhcp.dll b/obj/Debug/ln.dhcp.dll
index 3cb0a67..f212fae 100644
Binary files a/obj/Debug/ln.dhcp.dll and b/obj/Debug/ln.dhcp.dll differ
diff --git a/obj/Debug/ln.dhcp.pdb b/obj/Debug/ln.dhcp.pdb
index cda7738..1d5f917 100644
Binary files a/obj/Debug/ln.dhcp.pdb and b/obj/Debug/ln.dhcp.pdb differ
diff --git a/packages.config b/packages.config
new file mode 100644
index 0000000..39d1cce
--- /dev/null
+++ b/packages.config
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<packages>
+  <package id="Newtonsoft.Json" version="12.0.2" targetFramework="net47" />
+</packages>
\ No newline at end of file