diff --git a/doc/ospf6d.texi b/doc/ospf6d.texi
index d981820..d9bf06d 100644
--- a/doc/ospf6d.texi
+++ b/doc/ospf6d.texi
@@ -75,7 +75,7 @@
 @section OSPF6 interface
 
 @deffn {Interface Command} {ipv6 ospf6 cost COST} {}
-Sets interface's output cost.  Default value is 1.
+Sets interface's output cost.  Default value depends on the interface bandwidth.
 @end deffn
 
 @deffn {Interface Command} {ipv6 ospf6 hello-interval HELLOINTERVAL} {}
diff --git a/ospf6d/README b/ospf6d/README
index 883486f..6db347f 100644
--- a/ospf6d/README
+++ b/ospf6d/README
@@ -60,7 +60,7 @@
 
 INTERFACE NODE:
   ipv6 ospf6 cost COST
-    Sets the interface's output cost. default 1
+    Sets the interface's output cost. Depends on interface bandwidth by default.
 
   ipv6 ospf6 hello-interval HELLOINTERVAL
     Sets the interface's Hello Interval. default 10
diff --git a/ospf6d/ospf6_interface.c b/ospf6d/ospf6_interface.c
index b0f1119..e698893 100644
--- a/ospf6d/ospf6_interface.c
+++ b/ospf6d/ospf6_interface.c
@@ -117,6 +117,52 @@
     return OSPF_IFTYPE_BROADCAST;
 }
 
+static u_int32_t
+ospf6_interface_get_cost (struct ospf6_interface *oi)
+{
+  /* If all else fails, use default OSPF cost */
+  u_int32_t cost;
+  u_int32_t bw, refbw;
+
+  bw = oi->interface->bandwidth ? oi->interface->bandwidth : OSPF6_INTERFACE_BANDWIDTH;
+  refbw = OSPF6_REFERENCE_BANDWIDTH;
+
+  /* A specifed ip ospf cost overrides a calculated one. */
+  if (CHECK_FLAG (oi->flag, OSPF6_INTERFACE_NOAUTOCOST))
+    cost = oi->cost;
+  else
+    {
+      cost = (u_int32_t) ((double)refbw / (double)bw + (double)0.5);
+      if (cost < 1) cost = 1;
+      else if (cost > UINT32_MAX) cost = UINT32_MAX;
+    }
+
+  return cost;
+}
+
+static void
+ospf6_interface_recalculate_cost (struct ospf6_interface *oi)
+{
+  u_int32_t newcost;
+
+  newcost = ospf6_interface_get_cost (oi);
+  if (newcost == oi->cost) return;
+  oi->cost = newcost;
+
+  /* update cost held in route_connected list in ospf6_interface */
+  ospf6_interface_connected_route_update (oi->interface);
+
+  /* execute LSA hooks */
+  if (oi->area)
+    {
+      OSPF6_LINK_LSA_SCHEDULE (oi);
+      OSPF6_ROUTER_LSA_SCHEDULE (oi->area);
+      OSPF6_NETWORK_LSA_SCHEDULE (oi);
+      OSPF6_INTRA_PREFIX_LSA_SCHEDULE_TRANSIT (oi);
+      OSPF6_INTRA_PREFIX_LSA_SCHEDULE_STUB (oi->area);
+    }
+}
+
 /* Create new ospf6 interface structure */
 struct ospf6_interface *
 ospf6_interface_create (struct interface *ifp)
@@ -144,7 +190,6 @@
   oi->hello_interval = OSPF_HELLO_INTERVAL_DEFAULT;
   oi->dead_interval = OSPF_ROUTER_DEAD_INTERVAL_DEFAULT;
   oi->rxmt_interval = OSPF_RETRANSMIT_INTERVAL_DEFAULT;
-  oi->cost = OSPF6_INTERFACE_COST;
   oi->type = ospf6_default_iftype (ifp);
   oi->state = OSPF6_INTERFACE_DOWN;
   oi->flag = 0;
@@ -175,6 +220,9 @@
   oi->interface = ifp;
   ifp->info = oi;
 
+  /* Compute cost. */
+  oi->cost = ospf6_interface_get_cost(oi);
+
   return oi;
 }
 
@@ -658,6 +706,9 @@
 	return 0;
     }
 
+  /* Recompute cost */
+  ospf6_interface_recalculate_cost (oi);
+
   /* if already enabled, do nothing */
   if (oi->state > OSPF6_INTERFACE_DOWN)
     {
@@ -1214,19 +1265,37 @@
     return CMD_SUCCESS;
   
   oi->cost = lcost;
-  
-  /* update cost held in route_connected list in ospf6_interface */
-  ospf6_interface_connected_route_update (oi->interface);
+  SET_FLAG (oi->flag, OSPF6_INTERFACE_NOAUTOCOST);
 
-  /* execute LSA hooks */
-  if (oi->area)
-    {
-      OSPF6_LINK_LSA_SCHEDULE (oi);
-      OSPF6_ROUTER_LSA_SCHEDULE (oi->area);
-      OSPF6_NETWORK_LSA_SCHEDULE (oi);
-      OSPF6_INTRA_PREFIX_LSA_SCHEDULE_TRANSIT (oi);
-      OSPF6_INTRA_PREFIX_LSA_SCHEDULE_STUB (oi->area);
-    }
+  ospf6_interface_recalculate_cost(oi);
+
+  return CMD_SUCCESS;
+}
+
+DEFUN (no_ipv6_ospf6_cost,
+       no_ipv6_ospf6_cost_cmd,
+       "no ipv6 ospf6 cost",
+       NO_STR
+       IP6_STR
+       OSPF6_STR
+       "Calculate interface cost from bandwidth\n"
+       )
+{
+  struct ospf6_interface *oi;
+  struct interface *ifp;
+  unsigned long int lcost;
+
+  ifp = (struct interface *) vty->index;
+  assert (ifp);
+
+  oi = (struct ospf6_interface *) ifp->info;
+  if (oi == NULL)
+    oi = ospf6_interface_create (ifp);
+  assert (oi);
+
+  UNSET_FLAG (oi->flag, OSPF6_INTERFACE_NOAUTOCOST);
+
+  ospf6_interface_recalculate_cost(oi);
 
   return CMD_SUCCESS;
 }
@@ -1681,7 +1750,7 @@
       if (ifp->mtu6 != oi->ifmtu)
         vty_out (vty, " ipv6 ospf6 ifmtu %d%s", oi->ifmtu, VNL);
 
-      if (oi->cost != OSPF6_INTERFACE_COST)
+      if (CHECK_FLAG (oi->flag, OSPF6_INTERFACE_NOAUTOCOST))
         vty_out (vty, " ipv6 ospf6 cost %d%s",
                  oi->cost, VNL);
 
@@ -1764,6 +1833,7 @@
   install_element (INTERFACE_NODE, &interface_desc_cmd);
   install_element (INTERFACE_NODE, &no_interface_desc_cmd);
   install_element (INTERFACE_NODE, &ipv6_ospf6_cost_cmd);
+  install_element (INTERFACE_NODE, &no_ipv6_ospf6_cost_cmd);
   install_element (INTERFACE_NODE, &ipv6_ospf6_ifmtu_cmd);
   install_element (INTERFACE_NODE, &no_ipv6_ospf6_ifmtu_cmd);
   install_element (INTERFACE_NODE, &ipv6_ospf6_deadinterval_cmd);
diff --git a/ospf6d/ospf6_interface.h b/ospf6d/ospf6_interface.h
index 808f096..34f7523 100644
--- a/ospf6d/ospf6_interface.h
+++ b/ospf6d/ospf6_interface.h
@@ -128,6 +128,7 @@
 /* flags */
 #define OSPF6_INTERFACE_DISABLE      0x01
 #define OSPF6_INTERFACE_PASSIVE      0x02
+#define OSPF6_INTERFACE_NOAUTOCOST   0x04
 
 /* default values */
 #define OSPF6_INTERFACE_HELLO_INTERVAL 10
@@ -137,6 +138,9 @@
 #define OSPF6_INTERFACE_PRIORITY       1
 #define OSPF6_INTERFACE_TRANSDELAY     1
 #define OSPF6_INTERFACE_INSTANCE_ID    0
+#define OSPF6_INTERFACE_BANDWIDTH      10000   /* Kbps */
+#define OSPF6_REFERENCE_BANDWIDTH      100000  /* Kbps */
+
 
 
 /* Function Prototypes */
diff --git a/ospf6d/ospf6_zebra.c b/ospf6d/ospf6_zebra.c
index cffd767..8ee63fe 100644
--- a/ospf6d/ospf6_zebra.c
+++ b/ospf6d/ospf6_zebra.c
@@ -139,9 +139,9 @@
   
   if (IS_OSPF6_DEBUG_ZEBRA (RECV))
     zlog_debug ("Zebra Interface state change: "
-                "%s index %d flags %llx metric %d mtu %d",
+                "%s index %d flags %llx metric %d mtu %d bandwidth %d",
 		ifp->name, ifp->ifindex, (unsigned long long)ifp->flags, 
-		ifp->metric, ifp->mtu6);
+		ifp->metric, ifp->mtu6, ifp->bandwidth);
 
   ospf6_interface_state_update (ifp);
   return 0;