diff --git a/source/TR-181/include/wanmgr_dml.h b/source/TR-181/include/wanmgr_dml.h
index feee2ebe..720364cb 100644
--- a/source/TR-181/include/wanmgr_dml.h
+++ b/source/TR-181/include/wanmgr_dml.h
@@ -393,6 +393,7 @@ typedef struct _WANMGR_IPV6_DATA
     uint32_t ipv6_TimeOffset;
    /* Params to store the IPv6 IPC message */
    bool addrAssigned;           /**< Have we been assigned an IPv6 address ? */
+   bool addrConstructedFromIAPD; /**< TRUE if the WAN address was derived from the delegated prefix (IAPD) instead of a real IANA lease */
    uint32_t addrCmd;
    bool prefixAssigned;         /**< Have we been assigned a site prefix ? */
    uint32_t prefixCmd;
diff --git a/source/WanManager/wanmgr_dhcp_event_handler.c b/source/WanManager/wanmgr_dhcp_event_handler.c
index 1f0e1184..263f4c92 100644
--- a/source/WanManager/wanmgr_dhcp_event_handler.c
+++ b/source/WanManager/wanmgr_dhcp_event_handler.c
@@ -114,6 +114,7 @@ static void copyDhcpv6Data(WANMGR_IPV6_DATA* pDhcpv6Data, const DHCP_MGR_IPV6_MS
 #ifdef FEATURE_DSLITE_V2
     strncpy(pDhcpv6Data->aftr, leaseInfo->aftr, sizeof(pDhcpv6Data->aftr) - 1);
 #endif
+    pDhcpv6Data->addrConstructedFromIAPD = false;
     if(!pDhcpv6Data->addrAssigned && pDhcpv6Data->prefixAssigned)
     {
         /* In an IPv6 lease, if only IAPD is received and we never received IANA, 
diff --git a/source/WanManager/wanmgr_dhcpv6_apis.c b/source/WanManager/wanmgr_dhcpv6_apis.c
index 2aafa2dd..c6f9f4d1 100644
--- a/source/WanManager/wanmgr_dhcpv6_apis.c
+++ b/source/WanManager/wanmgr_dhcpv6_apis.c
@@ -1671,6 +1671,7 @@ int wanmgr_construct_wan_address_from_IAPD(WANMGR_IPV6_DATA *pIpv6DataNew)
     }
     
     pIpv6DataNew->addrAssigned = true;
+    pIpv6DataNew->addrConstructedFromIAPD = true;
     pIpv6DataNew->addrCmd = IFADDRCONF_ADD;
 
     CcspTraceInfo(("%s %d Calculated WAN address %s/128\n", __FUNCTION__, __LINE__, pIpv6DataNew->address));
@@ -1774,12 +1775,17 @@ ANSC_STATUS wanmgr_handle_dhcpv6_event_data(DML_VIRTUAL_IFACE * pVirtIf)
              */
         }
     }
-    else if(pDhcp6cInfoCur->addrAssigned && Ipv6DataNew.prefixAssigned)
+    else if(pDhcp6cInfoCur->addrAssigned && !pDhcp6cInfoCur->addrConstructedFromIAPD && Ipv6DataNew.prefixAssigned)
     {
         /* In an IPv6 lease, both IANA and IAPD details are sent together in a struct. 
          * If only one of them is renewed, the other field will be set to its default value.
          * In this scenario, we should not consider IANA or IAPD as deleted. 
          * If we reach this point, only IAPD has been renewed. Use the previous IANA details. 
+         *
+         * Note: This only applies when the previous address was a real IANA lease. If the previous
+         * address was derived from the delegated prefix (addrConstructedFromIAPD), we fall through
+         * to the branch below so the WAN address is re-derived from the newly delegated prefix
+         * instead of reusing the stale address from the old prefix. 
          */
 
         CcspTraceWarning(("%s %d IANA is not assigned in this IPC msg, but we have IANA configured from previous lease. Assuming only IAPD renewed. \n", __FUNCTION__, __LINE__));
@@ -1792,7 +1798,9 @@ ANSC_STATUS wanmgr_handle_dhcpv6_event_data(DML_VIRTUAL_IFACE * pVirtIf)
     {
         /* In an IPv6 lease, if only IAPD is received and we never received IANA, 
          * We can use the received IAPD to construct a Ipv6 /128 address which can be used for managerment and voice ...
-         * If we reach this point, only IAPD has been received. Calculate Wan Ipv6 address 
+         * If we reach this point, only IAPD has been received (either for the first time, or the
+         * previously assigned address was itself derived from a now-stale prefix). Calculate the
+         * WAN Ipv6 address from the newly delegated prefix. 
          */
 
         CcspTraceInfo(("IANA is not assigned by DHCPV6. Constructing WAN address from the IAPD for Wan Interface \n"));
@@ -1838,6 +1846,17 @@ ANSC_STATUS wanmgr_handle_dhcpv6_event_data(DML_VIRTUAL_IFACE * pVirtIf)
         CcspTraceWarning(("%s %d IAPD is not assigned in this IPC msg, but we have IAPD configured from previous lease. Assuming only IANA renewed. \n", __FUNCTION__, __LINE__));
         WanMgr_CopyPreviousPrefix(pDhcp6cInfoCur, &Ipv6DataNew);
     }
+    else if(!pNewIpcMsg->addrAssigned && !pNewIpcMsg->prefixAssigned &&
+            !IS_EMPTY_STRING(pNewIpcMsg->sitePrefix) &&
+            strcmp(pDhcp6cInfoCur->sitePrefix, pNewIpcMsg->sitePrefix) == 0)
+    {
+        /* Neither IANA nor IAPD was assigned in this lease (e.g. a DHCPv6 renew failure reports the
+         * previously delegated prefix with zero lifetimes). As the reported prefix matches the one
+         * currently in use, treat this as the WAN IPv6 lease no longer being valid and bring the
+         * IPv6 connection down. */
+        CcspTraceInfo(("%s %d Neither IANA nor IAPD assigned and prefix matches the current lease. Marking IPv6 connection down. \n", __FUNCTION__, __LINE__));
+        WanManager_UpdateInterfaceStatus(pVirtIf, WANMGR_IFACE_CONNECTION_IPV6_DOWN);
+    }
 
 #else
     /* dhcp6c receives an IPv6 address for WAN interface */
@@ -1949,9 +1968,13 @@ ANSC_STATUS wanmgr_handle_dhcpv6_event_data(DML_VIRTUAL_IFACE * pVirtIf)
 
     /* Even when dhcp6c is not used to get the WAN interface IP address,
      *  * use this message as a trigger to check the WAN interface IP.
-     *   * Maybe we've been assigned an address by SLAAC.*/
+     *   * Maybe we've been assigned an address by SLAAC.
+     * Skip this SLAAC detection when our current WAN address was derived from the delegated prefix
+     * (addrConstructedFromIAPD): in that case a global address still lingering on the interface is
+     * our own stale IAPD-derived /128, not a genuine SLAAC address, and must not be used to keep
+     * IPv6 up. Letting the code continue leaves 'connected' FALSE so IPv6 is not marked up. */
 
-    if (!pNewIpcMsg->addrAssigned)
+    if (!pNewIpcMsg->addrAssigned && !pDhcp6cInfoCur->addrConstructedFromIAPD)
     {
         char guAddrPrefix[IP_ADDR_LENGTH] = {0};
         char guAddr[IP_ADDR_LENGTH] = {0};