diff --git a/ports/linux/bip6.c b/ports/linux/bip6.c
index ec0ba002..c100d106 100644
--- a/ports/linux/bip6.c
+++ b/ports/linux/bip6.c
@@ -40,24 +40,52 @@
 #include "bacnet/bacdcode.h"
 #include "bacnet/config.h"
 #include "bacnet/datalink/bip6.h"
-#include "bacnet/basic/sys/debug.h"
 #include "bacnet/basic/object/device.h"
 #include "bacnet/basic/bbmd6/h_bbmd6.h"
 #include "bacport.h"
 
+/* enable debugging */
+static bool BIP6_Debug = false;
+#if PRINT_ENABLED
+#include <stdarg.h>
+#include <stdio.h>
+#define PRINTF(...) \
+    if (BIP6_Debug) { \
+        fprintf(stderr,__VA_ARGS__); \
+        fflush(stderr); \
+    }
+#else
+#define PRINTF(...)
+#endif
+
+/**
+ * @brief Print the IPv6 address with debug info
+ * @param str - debug info string
+ * @param addr - IPv4 address
+ */
 static void debug_print_ipv6(const char *str, const struct in6_addr *addr)
 {
-    debug_printf("BIP6: %s "
-                 "%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%"
-                 "02x:%02x%02x\n",
+    PRINTF("BIP6: %s "
+        "%02x%02x:%02x%02x:%02x%02x:%02x%02x:"
+        "%02x%02x:%02x%02x:%02x%02x:%02x%02x\n",
         str, (int)addr->s6_addr[0], (int)addr->s6_addr[1],
-        (int)addr->s6_addr[2], (int)addr->s6_addr[3], (int)addr->s6_addr[4],
-        (int)addr->s6_addr[5], (int)addr->s6_addr[6], (int)addr->s6_addr[7],
-        (int)addr->s6_addr[8], (int)addr->s6_addr[9], (int)addr->s6_addr[10],
-        (int)addr->s6_addr[11], (int)addr->s6_addr[12], (int)addr->s6_addr[13],
+        (int)addr->s6_addr[2], (int)addr->s6_addr[3],
+        (int)addr->s6_addr[4], (int)addr->s6_addr[5],
+        (int)addr->s6_addr[6], (int)addr->s6_addr[7],
+        (int)addr->s6_addr[8], (int)addr->s6_addr[9],
+        (int)addr->s6_addr[10], (int)addr->s6_addr[11],
+        (int)addr->s6_addr[12], (int)addr->s6_addr[13],
         (int)addr->s6_addr[14], (int)addr->s6_addr[15]);
 }
 
+/**
+ * @brief Enabled debug printing of BACnet/IPv4
+ */
+void bip6_debug_enable(void)
+{
+    BIP6_Debug = true;
+}
+
 /** @file linux/bip6.c  Initializes BACnet/IPv6 interface (Linux). */
 
 /* unix socket */
@@ -82,10 +110,12 @@ void bip6_set_interface(char *ifname)
         exit(1);
     }
     ifa_tmp = ifa;
-    debug_printf("BIP6: seeking interface: %s\n", ifname);
+    if (BIP6_Debug) {
+        PRINTF("BIP6: seeking interface: %s\n", ifname);
+    }
     while (ifa_tmp) {
         if ((ifa_tmp->ifa_addr) && (ifa_tmp->ifa_addr->sa_family == AF_INET6)) {
-            debug_printf("BIP6: found interface: %s\n", ifa_tmp->ifa_name);
+            PRINTF("BIP6: found interface: %s\n", ifa_tmp->ifa_name);
         }
         if ((ifa_tmp->ifa_addr) && (ifa_tmp->ifa_addr->sa_family == AF_INET6) &&
             (strcasecmp(ifa_tmp->ifa_name, ifname) == 0)) {
@@ -105,7 +135,7 @@ void bip6_set_interface(char *ifname)
         ifa_tmp = ifa_tmp->ifa_next;
     }
     if (!found) {
-        debug_printf("BIP6: unable to set interface: %s\n", ifname);
+        PRINTF("BIP6: unable to set interface: %s\n", ifname);
         exit(1);
     }
 }
@@ -350,6 +380,7 @@ uint16_t bip6_receive(
  */
 void bip6_cleanup(void)
 {
+    bvlc6_cleanup();
     if (BIP6_Socket != -1) {
         close(BIP6_Socket);
     }
@@ -391,7 +422,7 @@ bool bip6_init(char *ifname)
     if (BIP6_Addr.port == 0) {
         bip6_set_port(0xBAC0U);
     }
-    debug_printf("BIP6: IPv6 UDP port: 0x%04X\n", htons(BIP6_Addr.port));
+    PRINTF("BIP6: IPv6 UDP port: 0x%04X\n", htons(BIP6_Addr.port));
     if (BIP6_Broadcast_Addr.address[0] == 0) {
         bvlc6_address_set(&BIP6_Broadcast_Addr, BIP6_MULTICAST_SITE_LOCAL, 0, 0,
             0, 0, 0, 0, BIP6_MULTICAST_GROUP_ID);
diff --git a/ports/win32/bip6.c b/ports/win32/bip6.c
index 8496bcb0..336d92eb 100644
--- a/ports/win32/bip6.c
+++ b/ports/win32/bip6.c
@@ -50,9 +50,28 @@ static SOCKET BIP6_Socket = INVALID_SOCKET;
 static BACNET_IP6_ADDRESS BIP6_Addr;
 static BACNET_IP6_ADDRESS BIP6_Broadcast_Addr;
 
+/* enable debugging */
+static bool BIP6_Debug = false;
+#if PRINT_ENABLED
+#include <stdarg.h>
+#include <stdio.h>
+#define PRINTF(...) \
+    if (BIP6_Debug) { \
+        fprintf(stderr,__VA_ARGS__); \
+        fflush(stderr); \
+    }
+#else
+#define PRINTF(...)
+#endif
+
+/**
+ * @brief Print the IPv6 address with debug info
+ * @param str - debug info string
+ * @param addr - IPv4 address
+ */
 static void debug_print_ipv6(const char *str, const struct in6_addr *addr)
 {
-    debug_printf("BIP6: %s "
+    PRINTF("BIP6: %s "
                  "%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%"
                  "02x:%02x%02x\n",
         str, (int)addr->s6_addr[0], (int)addr->s6_addr[1],
@@ -63,6 +82,14 @@ static void debug_print_ipv6(const char *str, const struct in6_addr *addr)
         (int)addr->s6_addr[14], (int)addr->s6_addr[15]);
 }
 
+/**
+ * @brief Enabled debug printing of BACnet/IPv4
+ */
+void bip6_debug_enable(void)
+{
+    BIP6_Debug = true;
+}
+
 static LPSTR PrintError(int ErrorCode)
 {
     static char Message[1024];
@@ -104,7 +131,7 @@ void bip6_set_interface(char *ifname)
     Hints.ai_protocol = IPPROTO_UDP;
     Hints.ai_flags = AI_NUMERICHOST | AI_PASSIVE;
     snprintf(port, sizeof(port), "%u", BIP6_Addr.port);
-    debug_printf("BIP6: getaddrinfo - IPv6 address %s port %s\n", ifname, port);
+    PRINTF("BIP6: getaddrinfo - IPv6 address %s port %s\n", ifname, port);
     RetVal = getaddrinfo(ifname, &port[0], &Hints, &AddrInfo);
     if (RetVal != 0) {
         fprintf(stderr, "BIP6: getaddrinfo failed with error %d: %s\n", RetVal,
@@ -512,7 +539,7 @@ bool bip6_init(char *ifname)
     if (BIP6_Addr.port == 0) {
         bip6_set_port(0xBAC0U);
     }
-    debug_printf("BIP6: IPv6 UDP port: 0x%04X\n", BIP6_Addr.port);
+    PRINTF("BIP6: IPv6 UDP port: 0x%04X\n", BIP6_Addr.port);
     bip6_set_interface(ifname);
     if (BIP6_Broadcast_Addr.address[0] == 0) {
         bvlc6_address_set(&BIP6_Broadcast_Addr, BIP6_MULTICAST_LINK_LOCAL, 0, 0,
diff --git a/src/bacnet/basic/bbmd6/h_bbmd6.c b/src/bacnet/basic/bbmd6/h_bbmd6.c
index d5786387..ba13c91b 100644
--- a/src/bacnet/basic/bbmd6/h_bbmd6.c
+++ b/src/bacnet/basic/bbmd6/h_bbmd6.c
@@ -44,6 +44,20 @@
 #include "bacnet/basic/bbmd6/vmac.h"
 #include "bacnet/basic/bbmd6/h_bbmd6.h"
 
+
+static bool BVLC6_Debug;
+#if PRINT_ENABLED
+#include <stdarg.h>
+#include <stdio.h>
+#define PRINTF(...) \
+    if (BVLC6_Debug) { \
+        fprintf(stderr,__VA_ARGS__); \
+        fflush(stderr); \
+    }
+#else
+#define PRINTF(...)
+#endif
+
 /** result from a client request */
 static uint16_t BVLC6_Result_Code = BVLC6_RESULT_SUCCESSFUL_COMPLETION;
 /** incoming function */
@@ -68,6 +82,15 @@ static BACNET_IP6_BROADCAST_DISTRIBUTION_TABLE_ENTRY
 static BACNET_IP6_FOREIGN_DEVICE_TABLE_ENTRY FD_Table[MAX_FD6_ENTRIES];
 #endif
 
+/**
+ * @brief Enable debugging if print is enabled
+ */
+void bvlc6_debug_enable(void)
+{
+    BVLC6_Debug = true;
+    VMAC_Debug_Enable();
+}
+
 /** A timer function that is called about once a second.
  *
  * @param seconds - number of elapsed seconds since the last call
@@ -163,10 +186,21 @@ static bool bbmd6_add_vmac(uint32_t device_id, BACNET_IP6_ADDRESS *addr)
         vmac = VMAC_Find_By_Key(device_id);
         if (vmac) {
             /* already exists - replace? */
+            PRINTF("VMAC existing %u [", (unsigned int)device_id);
+            for (unsigned i = 0; i < vmac->mac_len; i++) {
+                PRINTF("%02X", vmac->mac[i]);
+            }
+            PRINTF("]\n");
+            PRINTF("VMAC ignoring %u [", (unsigned int)device_id);
+            for (unsigned i = 0; i < IP6_ADDRESS_MAX; i++) {
+                PRINTF("%02X", addr->address[i]);
+            }
+            PRINTF("%04X", addr->port);
+            PRINTF("]\n");
         } else if (bbmd6_address_to_vmac(&new_vmac, addr)) {
             /* new entry - add it! */
             status = VMAC_Add(device_id, &new_vmac);
-            debug_printf("BVLC6: Adding VMAC %lu.\n", (unsigned long)device_id);
+            PRINTF("BVLC6: Adding VMAC %lu.\n", (unsigned long)device_id);
         }
     }
 
@@ -216,7 +250,7 @@ static bool bbmd6_address_from_bacnet_address(
         if (status) {
             vmac = VMAC_Find_By_Key(device_id);
             if (vmac) {
-                debug_printf("BVLC6: Found VMAC %lu (len=%u).\n",
+                PRINTF("BVLC6: Found VMAC %lu (len=%u).\n",
                     (unsigned long)device_id, (unsigned)vmac->mac_len);
                 status = bbmd6_address_from_vmac(addr, vmac);
                 if (vmac_src) {
@@ -264,13 +298,13 @@ int bvlc6_send_pdu(BACNET_ADDRESS *dest,
             vmac_src = Device_Object_Instance_Number();
             mtu_len = bvlc6_encode_distribute_broadcast_to_network(
                 mtu, sizeof(mtu), vmac_src, pdu, pdu_len);
-            debug_printf("BVLC6: Sent Distribute-Broadcast-to-Network.\n");
+            PRINTF("BVLC6: Sent Distribute-Broadcast-to-Network.\n");
         } else {
             bip6_get_broadcast_addr(&bvlc_dest);
             vmac_src = Device_Object_Instance_Number();
             mtu_len = bvlc6_encode_original_broadcast(
                 mtu, sizeof(mtu), vmac_src, pdu, pdu_len);
-            debug_printf("BVLC6: Sent Original-Broadcast-NPDU.\n");
+            PRINTF("BVLC6: Sent Original-Broadcast-NPDU.\n");
         }
     } else if ((dest->net > 0) && (dest->len == 0)) {
         /* net > 0 and net < 65535 are network specific broadcast if len = 0 */
@@ -283,17 +317,17 @@ int bvlc6_send_pdu(BACNET_ADDRESS *dest,
         vmac_src = Device_Object_Instance_Number();
         mtu_len = bvlc6_encode_original_broadcast(
             mtu, sizeof(mtu), vmac_src, pdu, pdu_len);
-        debug_printf("BVLC6: Sent Original-Broadcast-NPDU.\n");
+        PRINTF("BVLC6: Sent Original-Broadcast-NPDU.\n");
     } else if (dest->mac_len == 3) {
         /* valid unicast */
         bbmd6_address_from_bacnet_address(&bvlc_dest, &vmac_dst, dest);
-        debug_printf("BVLC6: Sending to VMAC %lu.\n", (unsigned long)vmac_dst);
+        PRINTF("BVLC6: Sending to VMAC %lu.\n", (unsigned long)vmac_dst);
         vmac_src = Device_Object_Instance_Number();
         mtu_len = bvlc6_encode_original_unicast(
             mtu, sizeof(mtu), vmac_src, vmac_dst, pdu, pdu_len);
-        debug_printf("BVLC6: Sent Original-Unicast-NPDU.\n");
+        PRINTF("BVLC6: Sent Original-Unicast-NPDU.\n");
     } else {
-        debug_printf("BVLC6: Send failure. Invalid Address.\n");
+        PRINTF("BVLC6: Send failure. Invalid Address.\n");
         return -1;
     }
 
@@ -479,7 +513,7 @@ static void bbmd6_virtual_address_resolution_handler(
     uint32_t vmac_me = 0;
 
     if (addr && pdu) {
-        debug_printf("BIP6: Received Virtual-Address-Resolution.\n");
+        PRINTF("BIP6: Received Virtual-Address-Resolution.\n");
         if (bbmd6_address_match_self(addr)) {
             /* ignore messages from my IPv6 address */
         } else {
@@ -513,7 +547,7 @@ static void bbmd6_virtual_address_resolution_ack_handler(
     uint32_t vmac_dst = 0;
 
     if (addr && pdu) {
-        debug_printf("BIP6: Received Virtual-Address-Resolution-ACK.\n");
+        PRINTF("BIP6: Received Virtual-Address-Resolution-ACK.\n");
         if (bbmd6_address_match_self(addr)) {
             /* ignore messages from my IPv6 address */
         } else {
@@ -542,7 +576,7 @@ static void bbmd6_address_resolution_handler(
     uint32_t vmac_me = 0;
 
     if (addr && pdu) {
-        debug_printf("BIP6: Received Address-Resolution.\n");
+        PRINTF("BIP6: Received Address-Resolution.\n");
         if (bbmd6_address_match_self(addr)) {
             /* ignore messages from my IPv6 address */
         } else {
@@ -577,7 +611,7 @@ static void bbmd6_address_resolution_ack_handler(
     uint32_t vmac_dst = 0;
 
     if (addr && pdu) {
-        debug_printf("BIP6: Received Address-Resolution-ACK.\n");
+        PRINTF("BIP6: Received Address-Resolution-ACK.\n");
         if (bbmd6_address_match_self(addr)) {
             /* ignore messages from my IPv6 address */
         } else {
@@ -638,7 +672,7 @@ int bvlc6_bbmd_disabled_handler(BACNET_IP6_ADDRESS *addr,
                        incoming messages. */
                     bbmd6_add_vmac(vmac_src, addr);
                     bvlc6_vmac_address_set(src, vmac_src);
-                    debug_printf(
+                    PRINTF(
                         "BIP6: Received Result Code=%d\n", BVLC6_Result_Code);
                 }
                 break;
@@ -657,10 +691,10 @@ int bvlc6_bbmd_disabled_handler(BACNET_IP6_ADDRESS *addr,
             case BVLC6_ORIGINAL_UNICAST_NPDU:
                 /* This message is used to send directed NPDUs to
                    another B/IPv6 node or router. */
-                debug_printf("BIP6: Received Original-Unicast-NPDU.\n");
+                PRINTF("BIP6: Received Original-Unicast-NPDU.\n");
                 if (bbmd6_address_match_self(addr)) {
                     /* ignore messages from my IPv6 address */
-                    debug_printf("BIP6: Original-Unicast-NPDU is me!.\n");
+                    PRINTF("BIP6: Original-Unicast-NPDU is me!.\n");
                 } else {
                     function_len = bvlc6_decode_original_unicast(
                         pdu, pdu_len, &vmac_src, &vmac_dst, NULL, 0, &npdu_len);
@@ -673,20 +707,20 @@ int bvlc6_bbmd_disabled_handler(BACNET_IP6_ADDRESS *addr,
                             bvlc6_vmac_address_set(src, vmac_src);
                             offset = header_len + (function_len - npdu_len);
                         } else {
-                            debug_printf("BIP6: Original-Unicast-NPDU: "
+                            PRINTF("BIP6: Original-Unicast-NPDU: "
                                          "VMAC is not me!\n");
                         }
                     } else {
-                        debug_printf(
+                        PRINTF(
                             "BIP6: Original-Unicast-NPDU: Unable to decode!\n");
                     }
                 }
                 break;
             case BVLC6_ORIGINAL_BROADCAST_NPDU:
-                debug_printf("BIP6: Received Original-Broadcast-NPDU.\n");
+                PRINTF("BIP6: Received Original-Broadcast-NPDU.\n");
                 if (bbmd6_address_match_self(addr)) {
                     /* ignore messages from my IPv6 address */
-                    debug_printf("BIP6: Original-Broadcast-NPDU is me!\n");
+                    PRINTF("BIP6: Original-Broadcast-NPDU is me!\n");
                 } else {
                     function_len = bvlc6_decode_original_broadcast(
                         pdu, pdu_len, &vmac_src, NULL, 0, &npdu_len);
@@ -705,21 +739,21 @@ int bvlc6_bbmd_disabled_handler(BACNET_IP6_ADDRESS *addr,
                         npdu = &mtu[offset];
                         if (npdu_confirmed_service(npdu, npdu_len)) {
                             offset = 0;
-                            debug_printf(
+                            PRINTF(
                                 "BIP6: Original-Broadcast-NPDU: "
                                 "Confirmed Service! Discard!");
                         }
                     } else {
-                        debug_printf("BIP6: Original-Broadcast-NPDU: Unable to "
+                        PRINTF("BIP6: Original-Broadcast-NPDU: Unable to "
                                      "decode!\n");
                     }
                 }
                 break;
             case BVLC6_FORWARDED_NPDU:
-                debug_printf("BIP6: Received Forwarded-NPDU.\n");
+                PRINTF("BIP6: Received Forwarded-NPDU.\n");
                 if (bbmd6_address_match_self(addr)) {
                     /* ignore messages from my IPv6 address */
-                    debug_printf("BIP6: Forwarded-NPDU is me!\n");
+                    PRINTF("BIP6: Forwarded-NPDU is me!\n");
                 } else {
                     function_len = bvlc6_decode_forwarded_npdu(pdu, pdu_len,
                         &vmac_src, &fwd_address, NULL, 0, &npdu_len);
@@ -731,7 +765,7 @@ int bvlc6_bbmd_disabled_handler(BACNET_IP6_ADDRESS *addr,
                         bvlc6_vmac_address_set(src, vmac_src);
                         offset = header_len + (function_len - npdu_len);
                     } else {
-                        debug_printf(
+                        PRINTF(
                             "BIP6: Forwarded-NPDU: Unable to decode!\n");
                     }
                 }
@@ -761,7 +795,7 @@ int bvlc6_bbmd_disabled_handler(BACNET_IP6_ADDRESS *addr,
         if (send_result) {
             vmac_src = Device_Object_Instance_Number();
             bvlc6_send_result(addr, vmac_src, result_code);
-            debug_printf("BIP6: sent result code=%d\n", result_code);
+            PRINTF("BIP6: sent result code=%d\n", result_code);
         }
     }
 
@@ -820,7 +854,7 @@ int bvlc6_bbmd_enabled_handler(BACNET_IP6_ADDRESS *addr,
                        incoming messages. */
                     bbmd6_add_vmac(vmac_src, addr);
                     bvlc6_vmac_address_set(src, vmac_src);
-                    debug_printf(
+                    PRINTF(
                         "BIP6: Received Result Code=%d\n", BVLC6_Result_Code);
                 }
                 break;
@@ -839,9 +873,9 @@ int bvlc6_bbmd_enabled_handler(BACNET_IP6_ADDRESS *addr,
             case BVLC6_ORIGINAL_UNICAST_NPDU:
                 /* This message is used to send directed NPDUs to
                    another B/IPv6 node or router. */
-                debug_printf("BIP6: Received Original-Unicast-NPDU.\n");
+                PRINTF("BIP6: Received Original-Unicast-NPDU.\n");
                 if (bbmd6_address_match_self(addr)) {
-                    debug_printf("BIP6: Dropped Original-Unicast-NPDU.\n");
+                    PRINTF("BIP6: Dropped Original-Unicast-NPDU.\n");
                     /* ignore messages from my IPv6 address */
                     offset = 0;
                 } else {
@@ -860,7 +894,7 @@ int bvlc6_bbmd_enabled_handler(BACNET_IP6_ADDRESS *addr,
                 }
                 break;
             case BVLC6_ORIGINAL_BROADCAST_NPDU:
-                debug_printf("BIP6: Received Original-Broadcast-NPDU.\n");
+                PRINTF("BIP6: Received Original-Broadcast-NPDU.\n");
                 function_len = bvlc6_decode_original_broadcast(
                     pdu, pdu_len, &vmac_src, NULL, 0, &npdu_len);
                 if (function_len) {
@@ -873,7 +907,7 @@ int bvlc6_bbmd_enabled_handler(BACNET_IP6_ADDRESS *addr,
                        network layer. */
                     if (npdu_confirmed_service(npdu, npdu_len)) {
                         offset = 0;
-                        debug_printf(
+                        PRINTF(
                             "BIP6: Original-Broadcast-NPDU: "
                             "Confirmed Service! Discard!");
                     } else {
@@ -900,7 +934,7 @@ int bvlc6_bbmd_enabled_handler(BACNET_IP6_ADDRESS *addr,
                 }
                 break;
             case BVLC6_FORWARDED_NPDU:
-                debug_printf("BIP6: Received Forwarded-NPDU.\n");
+                PRINTF("BIP6: Received Forwarded-NPDU.\n");
                 function_len = bvlc6_decode_forwarded_npdu(
                     pdu, pdu_len, &vmac_src, &fwd_address, NULL, 0, &npdu_len);
                 if (function_len) {
@@ -959,7 +993,7 @@ int bvlc6_bbmd_enabled_handler(BACNET_IP6_ADDRESS *addr,
         if (send_result) {
             vmac_src = Device_Object_Instance_Number();
             bvlc6_send_result(addr, vmac_src, result_code);
-            debug_printf("BIP6: sent result code=%d\n", result_code);
+            PRINTF("BIP6: sent result code=%d\n", result_code);
         }
     }
 
diff --git a/src/bacnet/basic/bbmd6/h_bbmd6.h b/src/bacnet/basic/bbmd6/h_bbmd6.h
index 33341807..da8eaa65 100644
--- a/src/bacnet/basic/bbmd6/h_bbmd6.h
+++ b/src/bacnet/basic/bbmd6/h_bbmd6.h
@@ -84,6 +84,10 @@ extern "C" {
     void bvlc6_maintenance_timer(
         uint16_t seconds);
 
+    BACNET_STACK_EXPORT
+    void bvlc6_debug_enable(
+        void);
+
     BACNET_STACK_EXPORT
     void bvlc6_cleanup(void);
 
diff --git a/src/bacnet/basic/bbmd6/vmac.c b/src/bacnet/basic/bbmd6/vmac.c
index e67a20e2..4389a81f 100644
--- a/src/bacnet/basic/bbmd6/vmac.c
+++ b/src/bacnet/basic/bbmd6/vmac.c
@@ -42,6 +42,28 @@
 /* me! */
 #include "bacnet/basic/bbmd6/vmac.h"
 
+/* enable debugging */
+static bool VMAC_Debug = false;
+#if PRINT_ENABLED
+#include <stdarg.h>
+#include <stdio.h>
+#define PRINTF(...) \
+    if (VMAC_Debug) { \
+        fprintf(stderr,__VA_ARGS__); \
+        fflush(stderr); \
+    }
+#else
+#define PRINTF(...)
+#endif
+
+/**
+ * @brief Enable debugging if print is enabled
+ */
+void VMAC_Debug_Enable(void)
+{
+    VMAC_Debug = true;
+}
+
 /** @file
     Handle VMAC address binding */
 
@@ -90,7 +112,7 @@ bool VMAC_Add(uint32_t device_id, struct vmac_data *src)
             index = Keylist_Data_Add(VMAC_List, device_id, pVMAC);
             if (index >= 0) {
                 status = true;
-                printf("VMAC %u added.\n", (unsigned int)device_id);
+                PRINTF("VMAC %u added.\n", (unsigned int)device_id);
             }
         }
     }
@@ -234,11 +256,20 @@ bool VMAC_Find_By_Data(struct vmac_data *vmac, uint32_t *device_id)
 void VMAC_Cleanup(void)
 {
     struct vmac_data *pVMAC;
+    uint32_t device_id;
+    const int index = 0;
 
     if (VMAC_List) {
         do {
-            pVMAC = Keylist_Data_Pop(VMAC_List);
+            device_id = Keylist_Key(VMAC_List, index);
+            pVMAC = Keylist_Data_Delete_By_Index(VMAC_List, index);
             if (pVMAC) {
+                PRINTF("VMAC List: %lu [", (unsigned long)device_id);
+                /* print the MAC */
+                for (unsigned i = 0; i < pVMAC->mac_len; i++) {
+                    PRINTF("%02X", pVMAC->mac[i]);
+                }
+                PRINTF("]\n");
                 free(pVMAC);
             }
         } while (pVMAC);
@@ -255,7 +286,7 @@ void VMAC_Init(void)
     VMAC_List = Keylist_Create();
     if (VMAC_List) {
         atexit(VMAC_Cleanup);
-        printf("VMAC List initialized.\n");
+        PRINTF("VMAC List initialized.\n");
     }
 }
 
diff --git a/src/bacnet/basic/bbmd6/vmac.h b/src/bacnet/basic/bbmd6/vmac.h
index c206d931..0e6f9337 100644
--- a/src/bacnet/basic/bbmd6/vmac.h
+++ b/src/bacnet/basic/bbmd6/vmac.h
@@ -49,6 +49,8 @@ extern "C" {
     void VMAC_Cleanup(void);
     BACNET_STACK_EXPORT
     void VMAC_Init(void);
+    BACNET_STACK_EXPORT
+    void VMAC_Debug_Enable(void);
 
 #ifdef BAC_TEST
 #include "ctest.h"
diff --git a/src/bacnet/datalink/bip6.h b/src/bacnet/datalink/bip6.h
index 60f4a50e..44d29737 100644
--- a/src/bacnet/datalink/bip6.h
+++ b/src/bacnet/datalink/bip6.h
@@ -102,6 +102,10 @@ extern "C" {
     void bip6_receive_callback(
         void);
 
+    BACNET_STACK_EXPORT
+    void bip6_debug_enable(
+        void);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
diff --git a/src/bacnet/datalink/dlenv.c b/src/bacnet/datalink/dlenv.c
index 3f17edb3..ca917847 100644
--- a/src/bacnet/datalink/dlenv.c
+++ b/src/bacnet/datalink/dlenv.c
@@ -431,6 +431,11 @@ void dlenv_init(void)
 #endif
 #if defined(BACDL_BIP6)
     BACNET_IP6_ADDRESS addr;
+    pEnv = getenv("BACNET_BIP6_DEBUG");
+    if (pEnv) {
+        bip6_debug_enable();
+        bvlc6_debug_enable();
+    }
     pEnv = getenv("BACNET_BIP6_BROADCAST");
     if (pEnv) {
         bvlc6_address_set(&addr, (uint16_t)strtol(pEnv, NULL, 0), 0, 0, 0, 0, 0,