diff --git a/examples/drivers/windows/otApi/otApi.cpp b/examples/drivers/windows/otApi/otApi.cpp
index 8451c0522..f80da531c 100644
--- a/examples/drivers/windows/otApi/otApi.cpp
+++ b/examples/drivers/windows/otApi/otApi.cpp
@@ -1915,8 +1915,8 @@ otGetUnicastAddresses(
 
                 // Copy the necessary parameters
                 memcpy(&addrs[AddrCount].mAddress, &pAddr->sin6_addr, sizeof(pAddr->sin6_addr));
-                addrs[AddrCount].mPreferredLifetime = pUnicastAddr->PreferredLifetime;
-                addrs[AddrCount].mValidLifetime = pUnicastAddr->ValidLifetime;
+                addrs[AddrCount].mPreferred = pUnicastAddr->PreferredLifetime != 0;
+                addrs[AddrCount].mValid = pUnicastAddr->ValidLifetime != 0;
                 addrs[AddrCount].mPrefixLength = pUnicastAddr->OnLinkPrefixLength;
 
                 AddrCount++;
@@ -1979,8 +1979,8 @@ otAddUnicastAddress(
 
     memcpy(&newRow.Address.Ipv6.sin6_addr, &aAddress->mAddress, sizeof(IN6_ADDR));
     newRow.OnLinkPrefixLength = aAddress->mPrefixLength;
-    newRow.PreferredLifetime = aAddress->mPreferredLifetime;
-    newRow.ValidLifetime = aAddress->mValidLifetime;
+    newRow.PreferredLifetime = aAddress->mPreferred ? 0xffffffff : 0;
+    newRow.ValidLifetime = aAddress->mValid ? 0xffffffff : 0;
     newRow.PrefixOrigin = IpPrefixOriginOther;  // Derived from network XPANID
     newRow.SkipAsSource = FALSE;                // Allow automatic binding to this address (default)
 
diff --git a/examples/drivers/windows/otLwf/address.c b/examples/drivers/windows/otLwf/address.c
index 594ec8a81..259f1c8f5 100644
--- a/examples/drivers/windows/otLwf/address.c
+++ b/examples/drivers/windows/otLwf/address.c
@@ -78,8 +78,8 @@ otLwfOnAddressAdded(
 
         memcpy(&newRow.Address.Ipv6.sin6_addr, &Addr->mAddress, sizeof(IN6_ADDR));
         newRow.OnLinkPrefixLength = Addr->mPrefixLength;
-        newRow.PreferredLifetime = Addr->mPreferredLifetime;
-        newRow.ValidLifetime = Addr->mValidLifetime;
+        newRow.PreferredLifetime = Addr->mPreferred ? 0xffffffff : 0;
+        newRow.ValidLifetime = Addr->mValid ? 0xffffffff : 0;
         newRow.PrefixOrigin = IpPrefixOriginOther;  // Derived from network XPANID
         newRow.SkipAsSource = FALSE;                // Allow automatic binding to this address (default)
 
@@ -297,9 +297,9 @@ otLwfEventProcessingAddressChanged(
         {
             otNetifAddress otAddr = {0};
             memcpy(&otAddr.mAddress, pAddr, sizeof(IN6_ADDR));
-            otAddr.mPreferredLifetime = Row.PreferredLifetime;
+            otAddr.mPreferred = Row.PreferredLifetime != 0;
             otAddr.mPrefixLength = Row.OnLinkPrefixLength;
-            otAddr.mValidLifetime = Row.ValidLifetime;
+            otAddr.mValid = Row.ValidLifetime != 0;
 
             BOOLEAN ShouldDelete = FALSE;
             BOOLEAN AddedToCache = FALSE;
@@ -442,7 +442,9 @@ otLwfTunAddressesUpdated(
 
         {
             PIN6_ADDR pAddr = NULL;
-            otNetifAddress addr = { { 0 }, 0xFFFFFFFF, 0xFFFFFFFF, 0, 0, 0, NULL };
+            otNetifAddress addr = { { 0 }, 0, 1, 1, 0, 0, NULL };
+            uint32_t preferredLifetime = 0xFFFFFFFF;
+            uint32_t validLifetime = 0xFFFFFFFF;
 
             spinel_datatype_unpack(
                 entry_ptr, 
@@ -450,8 +452,11 @@ otLwfTunAddressesUpdated(
                 "6CLL", 
                 &pAddr, 
                 &addr.mPrefixLength, 
-                &addr.mValidLifetime, 
-                &addr.mPreferredLifetime);
+                &validLifetime,
+                &preferredLifetime);
+
+            addr.mPreferred = preferredLifetime != 0;
+            addr.mValid = validLifetime != 0;
 
             if (pAddr)
             {
diff --git a/examples/drivers/windows/otLwf/filter.h b/examples/drivers/windows/otLwf/filter.h
index 6cbd43946..e65dd018f 100644
--- a/examples/drivers/windows/otLwf/filter.h
+++ b/examples/drivers/windows/otLwf/filter.h
@@ -144,7 +144,7 @@ typedef struct _MS_FILTER
     IN6_ADDR                    otLinkLocalAddr;
     otNetifAddress              otAutoAddresses[OPENTHREAD_CONFIG_NUM_SLAAC_ADDRESSES];
 #if OPENTHREAD_ENABLE_DHCP6_CLIENT
-    otNetifAddress              otDhcpAddresses[OPENTHREAD_CONFIG_NUM_DHCP_PREFIXES];
+    otDhcpAddress               otDhcpAddresses[OPENTHREAD_CONFIG_NUM_DHCP_PREFIXES];
 #endif // OPENTHREAD_ENABLE_DHCP6_CLIENT
 
     union
diff --git a/examples/drivers/windows/otNodeApi/otNodeApi.cpp b/examples/drivers/windows/otNodeApi/otNodeApi.cpp
index 67a987a1a..e13413ca0 100644
--- a/examples/drivers/windows/otNodeApi/otNodeApi.cpp
+++ b/examples/drivers/windows/otNodeApi/otNodeApi.cpp
@@ -1338,8 +1338,8 @@ OTNODEAPI int32_t OTCALL otNodeAddIpAddr(otNode* aNode, const char *aAddr)
     if (error != kThreadError_None) return error;
 
     aAddress.mPrefixLength = 64;
-    aAddress.mPreferredLifetime = 0xffffffff;
-    aAddress.mValidLifetime = 0xffffffff;
+    aAddress.mPreferred = true;
+    aAddress.mValid = true;
     auto result = otAddUnicastAddress(aNode->mInstance, &aAddress);
     otLogFuncExit();
     return result;
diff --git a/include/dhcp6/dhcp6_client.h b/include/dhcp6/dhcp6_client.h
index dbb789f62..b5bb8cd13 100644
--- a/include/dhcp6/dhcp6_client.h
+++ b/include/dhcp6/dhcp6_client.h
@@ -35,6 +35,8 @@
 #ifndef OPENTHREAD_DHCP6_CLIENT_H_
 #define OPENTHREAD_DHCP6_CLIENT_H_
 
+#include <openthread-types.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -46,6 +48,17 @@ extern "C" {
  *
  */
 
+/**
+ * This structure represents a DHCPv6 address.
+ *
+ */
+typedef struct otDhcpAddress
+{
+    otNetifAddress mAddress;            ///< The network interface address.
+    uint32_t       mPreferredLifetime;  ///< The preferred lifetime.
+    uint32_t       mValidLifetime;      ///< The valid lifetime.
+} otDhcpAddress;
+
 /**
  * Update all automatically created IPv6 addresses for prefixes from current Network Data with DHCP procedure.
  *
@@ -55,7 +68,7 @@ extern "C" {
  * @param[in]     aContext       A pointer to data passed to aIidCreate function.
  *
  */
-void otDhcp6ClientUpdate(otInstance *aInstance, otNetifAddress *aAddresses, uint32_t aNumAddresses, void *aContext);
+void otDhcp6ClientUpdate(otInstance *aInstance, otDhcpAddress *aAddresses, uint32_t aNumAddresses, void *aContext);
 
 /**
  * @}
diff --git a/include/openthread-types.h b/include/openthread-types.h
index 70d021042..262f34731 100644
--- a/include/openthread-types.h
+++ b/include/openthread-types.h
@@ -900,11 +900,11 @@ typedef struct otBufferInfo
 typedef struct otNetifAddress
 {
     otIp6Address           mAddress;                 ///< The IPv6 unicast address.
-    uint32_t               mPreferredLifetime;       ///< The Preferred Lifetime.
-    uint32_t               mValidLifetime;           ///< The Valid lifetime.
     uint8_t                mPrefixLength;            ///< The Prefix length.
-    unsigned int           mScopeOverride : 4;       ///< The IPv6 scope of this address.
+    bool                   mPreferred : 1;           ///< TRUE if the address is preferred, FALSE otherwise.
+    bool                   mValid : 1;               ///< TRUE if the address is valid, FALSE otherwise.
     bool                   mScopeOverrideValid : 1;  ///< TRUE if the mScopeOverride value is valid, FALSE othewrise.
+    unsigned int           mScopeOverride : 4;       ///< The IPv6 scope of this address.
     struct otNetifAddress *mNext;                    ///< A pointer to the next network interface address.
 } otNetifAddress;
 
diff --git a/src/cli/cli.cpp b/src/cli/cli.cpp
index 21686159f..6e288c4eb 100644
--- a/src/cli/cli.cpp
+++ b/src/cli/cli.cpp
@@ -748,8 +748,8 @@ ThreadError Interpreter::ProcessIpAddrAdd(int argc, char *argv[])
 
     SuccessOrExit(error = otIp6AddressFromString(argv[0], &aAddress.mAddress));
     aAddress.mPrefixLength = 64;
-    aAddress.mPreferredLifetime = 0xffffffff;
-    aAddress.mValidLifetime = 0xffffffff;
+    aAddress.mPreferred = true;
+    aAddress.mValid = true;
     error = otAddUnicastAddress(mInstance, &aAddress);
 
 exit:
diff --git a/src/cli/cli.hpp b/src/cli/cli.hpp
index 00eed6ef2..f09b6a1f7 100644
--- a/src/cli/cli.hpp
+++ b/src/cli/cli.hpp
@@ -248,7 +248,7 @@ private:
 
     otNetifAddress  mSlaacAddresses[OPENTHREAD_CONFIG_NUM_SLAAC_ADDRESSES];
 #if OPENTHREAD_ENABLE_DHCP6_CLIENT
-    otNetifAddress  mDhcpAddresses[OPENTHREAD_CONFIG_NUM_DHCP_PREFIXES];
+    otDhcpAddress  mDhcpAddresses[OPENTHREAD_CONFIG_NUM_DHCP_PREFIXES];
 #endif // OPENTHREAD_ENABLE_DHCP6_CLIENT
 
     otInstance *mInstance;
diff --git a/src/core/net/dhcp6_client.cpp b/src/core/net/dhcp6_client.cpp
index a41b48125..23a72c328 100644
--- a/src/core/net/dhcp6_client.cpp
+++ b/src/core/net/dhcp6_client.cpp
@@ -71,13 +71,13 @@ Dhcp6Client::Dhcp6Client(ThreadNetif &aThreadNetif) :
     mIdentityAssociationAvail = &mIdentityAssociations[0];
 }
 
-void Dhcp6Client::UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddresses, uint32_t aNumAddresses,
+void Dhcp6Client::UpdateAddresses(otInstance *aInstance, otDhcpAddress *aAddresses, uint32_t aNumAddresses,
                                   void *aContext)
 {
     (void)aContext;
     bool found = false;;
     bool newAgent = false;
-    otNetifAddress *address = NULL;
+    otDhcpAddress *address = NULL;
     otNetworkDataIterator iterator;
     otBorderRouterConfig config;
 
@@ -104,8 +104,9 @@ void Dhcp6Client::UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddres
                 continue;
             }
 
-            if ((otIp6PrefixMatch(&(address->mAddress), &(config.mPrefix.mPrefix)) >= address->mPrefixLength) &&
-                (config.mPrefix.mLength == address->mPrefixLength))
+            if ((otIp6PrefixMatch(&(address->mAddress.mAddress), &(config.mPrefix.mPrefix)) >=
+                 address->mAddress.mPrefixLength) &&
+                (config.mPrefix.mLength == address->mAddress.mPrefixLength))
             {
                 found = true;
                 break;
@@ -114,7 +115,7 @@ void Dhcp6Client::UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddres
 
         if (!found)
         {
-            otRemoveUnicastAddress(aInstance, &(address->mAddress));
+            otRemoveUnicastAddress(aInstance, &(address->mAddress.mAddress));
             RemoveIdentityAssociation(config.mRloc16, config.mPrefix);
             memset(address, 0, sizeof(*address));
         }
@@ -136,13 +137,14 @@ void Dhcp6Client::UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddres
         {
             address = &mAddresses[i];
 
-            if (address->mPrefixLength == 0)
+            if (address->mAddress.mPrefixLength == 0)
             {
                 continue;
             }
 
-            if ((otIp6PrefixMatch(&(config.mPrefix.mPrefix), &(address->mAddress)) >= config.mPrefix.mLength) &&
-                (config.mPrefix.mLength == address->mPrefixLength))
+            if ((otIp6PrefixMatch(&(config.mPrefix.mPrefix), &(address->mAddress.mAddress)) >=
+                 config.mPrefix.mLength) &&
+                (config.mPrefix.mLength == address->mAddress.mPrefixLength))
             {
                 found = true;
                 break;
@@ -155,7 +157,7 @@ void Dhcp6Client::UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddres
             {
                 address = &mAddresses[i];
 
-                if (address->mPrefixLength != 0)
+                if (address->mAddress.mPrefixLength != 0)
                 {
                     continue;
                 }
@@ -163,8 +165,8 @@ void Dhcp6Client::UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddres
                 memset(address, 0, sizeof(*address));
 
                 // suppose all configured prefix are ::/64
-                memcpy(address->mAddress.mFields.m8, config.mPrefix.mPrefix.mFields.m8, 8);
-                address->mPrefixLength = config.mPrefix.mLength;
+                memcpy(address->mAddress.mAddress.mFields.m8, config.mPrefix.mPrefix.mFields.m8, 8);
+                address->mAddress.mPrefixLength = config.mPrefix.mLength;
 
                 AddIdentityAssociation(config.mRloc16, config.mPrefix);
                 newAgent = true;
@@ -662,7 +664,7 @@ ThreadError Dhcp6Client::ProcessIaAddress(Message &aMessage, uint16_t aOffset)
 {
     ThreadError error = kThreadError_None;
     IdentityAssociation *identityAssociation = NULL;
-    otNetifAddress *address = NULL;
+    otDhcpAddress *address = NULL;
     otIp6Prefix *prefix  = NULL;
 
     IaAddress option;
@@ -680,12 +682,14 @@ ThreadError Dhcp6Client::ProcessIaAddress(Message &aMessage, uint16_t aOffset)
             continue;
         }
 
-        if (otIp6PrefixMatch(&(address->mAddress), option.GetAddress()) >= address->mPrefixLength)
+        if (otIp6PrefixMatch(&(address->mAddress.mAddress), option.GetAddress()) >= address->mAddress.mPrefixLength)
         {
-            memcpy(address->mAddress.mFields.m8, option.GetAddress()->mFields.m8, sizeof(otIp6Address));
+            memcpy(address->mAddress.mAddress.mFields.m8, option.GetAddress()->mFields.m8, sizeof(otIp6Address));
             address->mPreferredLifetime = option.GetPreferredLifetime();
             address->mValidLifetime = option.GetValidLifetime();
-            otAddUnicastAddress(mNetif.GetInstance(), address);
+            address->mAddress.mPreferred = address->mPreferredLifetime != 0;
+            address->mAddress.mValid = address->mValidLifetime != 0;
+            otAddUnicastAddress(mNetif.GetInstance(), &address->mAddress);
             break;
         }
     }
diff --git a/src/core/net/dhcp6_client.hpp b/src/core/net/dhcp6_client.hpp
index 190119f0e..74111ca5a 100644
--- a/src/core/net/dhcp6_client.hpp
+++ b/src/core/net/dhcp6_client.hpp
@@ -34,6 +34,8 @@
 #ifndef DHCP6_CLIENT_HPP_
 #define DHCP6_CLIENT_HPP_
 
+#include <dhcp6/dhcp6_client.h>
+
 #include <common/message.hpp>
 #include <common/timer.hpp>
 #include <common/trickle_timer.hpp>
@@ -185,7 +187,7 @@ public:
      * @param[in]     aContext      A pointer to IID creator-specific context data.
      *
      */
-    void UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddresses, uint32_t aNumAddresses, void *aContext);
+    void UpdateAddresses(otInstance *aInstance, otDhcpAddress *aAddresses, uint32_t aNumAddresses, void *aContext);
 
 private:
     ThreadError Start(void);
@@ -228,7 +230,7 @@ private:
 
     uint8_t mTransactionId[kTransactionIdSize];
     uint32_t mStartTime;
-    otNetifAddress *mAddresses;
+    otDhcpAddress *mAddresses;
     uint32_t mNumAddresses;
 
     IdentityAssociation mIdentityAssociations[OPENTHREAD_CONFIG_NUM_DHCP_PREFIXES];
diff --git a/src/core/net/dhcp6_server.cpp b/src/core/net/dhcp6_server.cpp
index b0d8b0f6f..5b25b96fb 100644
--- a/src/core/net/dhcp6_server.cpp
+++ b/src/core/net/dhcp6_server.cpp
@@ -80,7 +80,7 @@ ThreadError Dhcp6Server::UpdateService(void)
     {
         found = false;
 
-        if (mAgentsAloc[i].mValidLifetime == 0)
+        if (!mAgentsAloc[i].mValid)
         {
             continue;
         }
@@ -109,7 +109,7 @@ ThreadError Dhcp6Server::UpdateService(void)
         {
             mNetworkDataLeader.GetContext(address->mFields.m8[15], lowpanContext);
             mNetif.RemoveUnicastAddress(mAgentsAloc[i]);
-            mAgentsAloc[i].mValidLifetime = 0;
+            mAgentsAloc[i].mValid = false;
             RemovePrefixAgent(lowpanContext.mPrefix);
         }
     }
@@ -132,7 +132,7 @@ ThreadError Dhcp6Server::UpdateService(void)
         {
             address = &(mAgentsAloc[i].GetAddress());
 
-            if ((mAgentsAloc[i].mValidLifetime != 0) && (address->mFields.m8[15] == lowpanContext.mContextId))
+            if ((mAgentsAloc[i].mValid) && (address->mFields.m8[15] == lowpanContext.mContextId))
             {
                 found = true;
                 break;
@@ -147,7 +147,7 @@ ThreadError Dhcp6Server::UpdateService(void)
 
         for (i = 0; i < OPENTHREAD_CONFIG_NUM_DHCP_PREFIXES; i++)
         {
-            if (mAgentsAloc[i].mValidLifetime == 0)
+            if (!mAgentsAloc[i].mValid)
             {
                 address = &(mAgentsAloc[i].GetAddress());
                 memcpy(address, mMle.GetMeshLocalPrefix(), 8);
@@ -157,8 +157,8 @@ ThreadError Dhcp6Server::UpdateService(void)
                 address->mFields.m8[14] = Mle::kAloc16Mask;
                 address->mFields.m8[15] = lowpanContext.mContextId;
                 mAgentsAloc[i].mPrefixLength = 128;
-                mAgentsAloc[i].mPreferredLifetime = 0xffffffff;
-                mAgentsAloc[i].mValidLifetime = 0xffffffff;
+                mAgentsAloc[i].mPreferred = true;
+                mAgentsAloc[i].mValid = true;
                 mNetif.AddUnicastAddress(mAgentsAloc[i]);
                 AddPrefixAgent(config.mPrefix);
                 break;
diff --git a/src/core/net/ip6.cpp b/src/core/net/ip6.cpp
index f7d44af05..c7b9e501f 100644
--- a/src/core/net/ip6.cpp
+++ b/src/core/net/ip6.cpp
@@ -1010,7 +1010,7 @@ const NetifUnicastAddress *Ip6::SelectSourceAddress(MessageInfo &aMessageInfo)
                     rvalIface = candidateId;
                 }
             }
-            else if (addr->mPreferredLifetime != 0 && rvalAddr->mPreferredLifetime == 0)
+            else if (addr->mPreferred && !rvalAddr->mPreferred)
             {
                 // Rule 3: Avoid deprecated addresses
                 rvalAddr = addr;
diff --git a/src/core/net/netif.cpp b/src/core/net/netif.cpp
index 1d6a3b1cd..6da6c6886 100644
--- a/src/core/net/netif.cpp
+++ b/src/core/net/netif.cpp
@@ -372,9 +372,9 @@ ThreadError Netif::AddExternalUnicastAddress(const NetifUnicastAddress &aAddress
         {
             VerifyOrExit(GetExtUnicastAddressIndex(cur) != -1, error = kThreadError_InvalidArgs);
 
-            cur->mPreferredLifetime = aAddress.mPreferredLifetime;
-            cur->mValidLifetime = aAddress.mValidLifetime;
             cur->mPrefixLength = aAddress.mPrefixLength;
+            cur->mPreferred = aAddress.mPreferred;
+            cur->mValid = aAddress.mValid;
             ExitNow();
         }
     }
diff --git a/src/core/openthread.cpp b/src/core/openthread.cpp
index 144b9e05b..111d8984a 100644
--- a/src/core/openthread.cpp
+++ b/src/core/openthread.cpp
@@ -1020,7 +1020,7 @@ void otDhcp6ServerUpdate(otInstance *aInstance)
 #endif  // OPENTHREAD_ENABLE_DHCP6_SERVER
 
 #if OPENTHREAD_ENABLE_DHCP6_CLIENT
-void otDhcp6ClientUpdate(otInstance *aInstance, otNetifAddress *aAddresses, uint32_t aNumAddresses, void *aContext)
+void otDhcp6ClientUpdate(otInstance *aInstance, otDhcpAddress *aAddresses, uint32_t aNumAddresses, void *aContext)
 {
     aInstance->mThreadNetif.GetDhcp6Client().UpdateAddresses(aInstance, aAddresses, aNumAddresses, aContext);
 }
diff --git a/src/core/thread/mle.cpp b/src/core/thread/mle.cpp
index b4cac2f1e..29346d1a0 100644
--- a/src/core/thread/mle.cpp
+++ b/src/core/thread/mle.cpp
@@ -111,14 +111,14 @@ Mle::Mle(ThreadNetif &aThreadNetif) :
     mLinkLocal64.GetAddress().mFields.m16[0] = HostSwap16(0xfe80);
     mLinkLocal64.GetAddress().SetIid(*mMac.GetExtAddress());
     mLinkLocal64.mPrefixLength = 64;
-    mLinkLocal64.mPreferredLifetime = 0xffffffff;
-    mLinkLocal64.mValidLifetime = 0xffffffff;
+    mLinkLocal64.mPreferred = true;
+    mLinkLocal64.mValid = true;
     mNetif.AddUnicastAddress(mLinkLocal64);
 
     // Leader Aloc
     mLeaderAloc.mPrefixLength = 128;
-    mLeaderAloc.mPreferredLifetime = 0xffffffff;
-    mLeaderAloc.mValidLifetime = 0xffffffff;
+    mLeaderAloc.mPreferred = true;
+    mLeaderAloc.mValid = true;
     mLeaderAloc.mScopeOverride = Ip6::Address::kRealmLocalScope;
     mLeaderAloc.mScopeOverrideValid = true;
 
@@ -137,8 +137,8 @@ Mle::Mle(ThreadNetif &aThreadNetif) :
     }
 
     mMeshLocal64.mPrefixLength = 64;
-    mMeshLocal64.mPreferredLifetime = 0xffffffff;
-    mMeshLocal64.mValidLifetime = 0xffffffff;
+    mMeshLocal64.mPreferred = true;
+    mMeshLocal64.mValid = true;
     SetMeshLocalPrefix(mMeshLocal64.GetAddress().mFields.m8); // Also calls AddUnicastAddress
 
     // mesh-local 16
@@ -146,8 +146,8 @@ Mle::Mle(ThreadNetif &aThreadNetif) :
     mMeshLocal16.GetAddress().mFields.m16[5] = HostSwap16(0x00ff);
     mMeshLocal16.GetAddress().mFields.m16[6] = HostSwap16(0xfe00);
     mMeshLocal16.mPrefixLength = 64;
-    mMeshLocal16.mPreferredLifetime = 0xffffffff;
-    mMeshLocal16.mValidLifetime = 0xffffffff;
+    mMeshLocal16.mPreferred = true;
+    mMeshLocal16.mValid = true;
     mMeshLocal16.mScopeOverride = Ip6::Address::kRealmLocalScope;
     mMeshLocal16.mScopeOverrideValid = true;
 
diff --git a/src/core/utils/slaac_address.cpp b/src/core/utils/slaac_address.cpp
index af70518a7..a0f814d18 100644
--- a/src/core/utils/slaac_address.cpp
+++ b/src/core/utils/slaac_address.cpp
@@ -63,7 +63,7 @@ void Slaac::UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddresses, u
         otNetifAddress *address = &aAddresses[i];
         bool found = false;
 
-        if (address->mValidLifetime == 0)
+        if (!address->mValid)
         {
             continue;
         }
@@ -88,7 +88,7 @@ void Slaac::UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddresses, u
         if (!found)
         {
             otRemoveUnicastAddress(aInstance, &address->mAddress);
-            address->mValidLifetime = 0;
+            address->mValid = false;
         }
     }
 
@@ -108,7 +108,7 @@ void Slaac::UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddresses, u
         {
             otNetifAddress *address = &aAddresses[i];
 
-            if (address->mValidLifetime == 0)
+            if (!address->mValid)
             {
                 continue;
             }
@@ -127,7 +127,7 @@ void Slaac::UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddresses, u
             {
                 otNetifAddress *address = &aAddresses[i];
 
-                if (address->mValidLifetime != 0)
+                if (address->mValid)
                 {
                     continue;
                 }
@@ -136,8 +136,8 @@ void Slaac::UpdateAddresses(otInstance *aInstance, otNetifAddress *aAddresses, u
                 memcpy(&address->mAddress, &config.mPrefix.mPrefix, 8);
 
                 address->mPrefixLength = config.mPrefix.mLength;
-                address->mPreferredLifetime = config.mPreferred ? 0xffffffff : 0;
-                address->mValidLifetime = 0xffffffff;
+                address->mPreferred = config.mPreferred;
+                address->mValid = true;
 
                 if (aIidCreator(aInstance, address, aContext) != kThreadError_None)
                 {
diff --git a/src/ncp/ncp_base.cpp b/src/ncp/ncp_base.cpp
index fc8de78f0..3f2753dbc 100644
--- a/src/ncp/ncp_base.cpp
+++ b/src/ncp/ncp_base.cpp
@@ -2374,8 +2374,8 @@ ThreadError NcpBase::GetPropertyHandler_IPV6_ADDRESS_TABLE(uint8_t header, spine
                                       "T(6CLL).",
                                       &address->mAddress,
                                       address->mPrefixLength,
-                                      address->mPreferredLifetime,
-                                      address->mValidLifetime
+                                      address->mPreferred ? 0xffffffff : 0,
+                                      address->mValid ? 0xffffffff : 0
                                   ));
     }
 
@@ -4750,8 +4750,8 @@ ThreadError NcpBase::InsertPropertyHandler_IPV6_ADDRESS_TABLE(uint8_t header, sp
 
     netif_addr.mAddress = *addr_ptr;
     netif_addr.mPrefixLength = prefix_len;
-    netif_addr.mPreferredLifetime = preferred_lifetime;
-    netif_addr.mValidLifetime = valid_lifetime;
+    netif_addr.mPreferred = preferred_lifetime != 0;
+    netif_addr.mValid = valid_lifetime != 0;
 
     errorCode = otAddUnicastAddress(mInstance, &netif_addr);