diff --git a/ospfd/ospf_ase.c b/ospfd/ospf_ase.c
new file mode 100644
index 0000000..9194c56
--- /dev/null
+++ b/ospfd/ospf_ase.c
@@ -0,0 +1,838 @@
+/*
+ * OSPF AS external route calculation.
+ * Copyright (C) 1999, 2000 Alex Zinin, Toshiaki Takada
+ *
+ * This file is part of GNU Zebra.
+ *
+ * GNU Zebra is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * GNU Zebra is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Zebra; see the file COPYING.  If not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#include <zebra.h>
+
+#include "thread.h"
+#include "memory.h"
+#include "hash.h"
+#include "linklist.h"
+#include "prefix.h"
+#include "if.h"
+#include "table.h"
+#include "vty.h"
+#include "log.h"
+
+#include "ospfd/ospfd.h"
+#include "ospfd/ospf_interface.h"
+#include "ospfd/ospf_ism.h"
+#include "ospfd/ospf_asbr.h"
+#include "ospfd/ospf_lsa.h"
+#include "ospfd/ospf_lsdb.h"
+#include "ospfd/ospf_neighbor.h"
+#include "ospfd/ospf_nsm.h"
+#include "ospfd/ospf_spf.h"
+#include "ospfd/ospf_route.h"
+#include "ospfd/ospf_ase.h"
+#include "ospfd/ospf_zebra.h"
+#include "ospfd/ospf_dump.h"
+
+#define DEBUG
+
+struct ospf_route *
+ospf_find_asbr_route (struct route_table *rtrs, struct prefix_ipv4 *asbr)
+{
+  struct route_node *rn;
+  struct ospf_route *or, *best = NULL;
+  listnode node;
+  list chosen;
+
+  /* Sanity check. */
+  if (rtrs == NULL)
+    return NULL;
+
+  rn = route_node_lookup (rtrs, (struct prefix *) asbr);
+  if (! rn)
+    return NULL;
+
+  route_unlock_node (rn);
+
+  chosen = list_new ();
+
+  /* First try to find intra-area non-bb paths. */
+  if (!CHECK_FLAG (ospf_top->config, OSPF_RFC1583_COMPATIBLE))
+    for (node = listhead ((list) rn->info); node; nextnode (node))
+      if ((or = getdata (node)) != NULL)
+	if (or->cost < OSPF_LS_INFINITY)
+	  if (!OSPF_IS_AREA_ID_BACKBONE (or->u.std.area_id) &&
+	      or->path_type == OSPF_PATH_INTRA_AREA)
+	    listnode_add (chosen, or);
+
+  /* If none is found -- look through all. */
+  if (listcount (chosen) == 0)
+    {
+      list_free (chosen);
+      chosen = rn->info;
+    }
+
+  /* Now find the route with least cost. */
+  for (node = listhead (chosen); node; nextnode (node))
+    if ((or = getdata (node)) != NULL)
+      if (or->cost < OSPF_LS_INFINITY)
+	{
+	  if (best == NULL)
+	    best = or;
+	  else if (best->cost > or->cost)
+	    best = or;
+	  else if (best->cost == or->cost &&
+		   IPV4_ADDR_CMP (&best->u.std.area_id,
+				  &or->u.std.area_id) < 0)
+	    best = or;
+	}
+
+  if (chosen != rn->info)
+    list_delete (chosen);
+
+  return best;
+}
+
+struct ospf_route * 
+ospf_find_asbr_route_through_area (struct route_table *rtrs, 
+				   struct prefix_ipv4 *asbr, 
+				   struct ospf_area *area)
+{
+  struct route_node *rn;
+
+  /* Sanity check. */
+  if (rtrs == NULL)
+    return NULL;
+
+  rn = route_node_lookup (rtrs, (struct prefix *) asbr);
+ 
+  if (rn)
+    {
+      listnode node;
+      struct ospf_route *or;
+
+      route_unlock_node (rn);
+
+      for (node = listhead ((list) rn->info); node; nextnode (node))
+	if ((or = getdata (node)) != NULL)
+	  if (IPV4_ADDR_SAME (&or->u.std.area_id, &area->area_id))
+	    return or;
+    }
+
+  return NULL;
+}
+
+void
+ospf_ase_complete_direct_routes (struct ospf_route *ro, struct in_addr nexthop)
+{
+  listnode node;
+  struct ospf_path *op;
+
+  for (node = listhead (ro->path); node; nextnode (node))
+    if ((op = getdata (node)) != NULL)
+      if (op->nexthop.s_addr == 0)
+	op->nexthop.s_addr = nexthop.s_addr;
+}
+
+int
+ospf_ase_forward_address_check (struct in_addr fwd_addr)
+{
+  listnode ifn;
+  struct ospf_interface *oi;
+
+  for (ifn = listhead (ospf_top->oiflist); ifn; nextnode (ifn))
+    if ((oi = getdata (ifn)) != NULL)
+      if (if_is_up (oi->ifp))
+	if (oi->type != OSPF_IFTYPE_VIRTUALLINK)
+	  if (IPV4_ADDR_SAME (&oi->address->u.prefix4, &fwd_addr))
+	    return 0;
+  
+  return 1;
+}
+
+/* Calculate ASBR route. */
+struct ospf_route *
+ospf_ase_calculate_asbr_route (struct route_table *rt_network,
+			       struct route_table *rt_router,
+			       struct as_external_lsa *al)
+{
+  struct prefix_ipv4 asbr;
+  struct ospf_route *asbr_route;
+  struct route_node *rn;
+
+  /* Find ASBR route from Router routing table. */
+  asbr.family = AF_INET;
+  asbr.prefix = al->header.adv_router;
+  asbr.prefixlen = IPV4_MAX_BITLEN;
+  apply_mask_ipv4 (&asbr);
+
+  asbr_route = ospf_find_asbr_route (rt_router, &asbr);
+
+  if (asbr_route == NULL)
+    {
+      zlog_info ("ospf_ase_calculate(): Route to ASBR %s not found",
+		 inet_ntoa (asbr.prefix));
+      return NULL;
+    }
+
+  if (!(asbr_route->u.std.flags & ROUTER_LSA_EXTERNAL))
+    {
+      zlog_info ("ospf_ase_calculate(): Originating router is not an ASBR");
+      return NULL;
+    }
+   
+  if (al->e[0].fwd_addr.s_addr != 0)
+    {
+      zlog_info ("ospf_ase_calculate(): "
+		 "Forwarding address is not 0.0.0.0.");
+
+      if (! ospf_ase_forward_address_check (al->e[0].fwd_addr))
+	{
+	  zlog_info ("ospf_ase_calculate(): "
+		     "Forwarding address is one of our addresses, Ignore.");
+	  return NULL;
+        }
+
+      zlog_info ("ospf_ase_calculate(): "
+		 "Looking up in the Network Routing Table.");
+
+      /* Looking up the path to the fwd_addr from Network route. */
+      asbr.family = AF_INET;
+      asbr.prefix = al->e[0].fwd_addr;
+      asbr.prefixlen = IPV4_MAX_BITLEN;
+
+      rn = route_node_match (rt_network, (struct prefix *) &asbr);
+   
+      if (rn == NULL)
+	{
+	  zlog_info ("ospf_ase_calculate(): "
+		     "Couldn't find a route to the forwarding address.");
+	  return NULL;
+	}
+
+      route_unlock_node (rn);
+
+      if ((asbr_route = rn->info) == NULL)
+	{
+	  zlog_info ("ospf_ase_calculate(): "
+		     "Somehow OSPF route to ASBR is lost");
+	  return NULL;
+	}
+    }
+
+  return asbr_route;
+}
+
+struct ospf_route *
+ospf_ase_calculate_new_route (struct ospf_lsa *lsa,
+			      struct ospf_route *asbr_route, u_int32_t metric)
+{
+  struct as_external_lsa *al;
+  struct ospf_route *new;
+
+  al = (struct as_external_lsa *) lsa->data;
+
+  new = ospf_route_new ();
+
+  /* Set redistributed type -- does make sense? */
+  /* new->type = type; */
+  new->id = al->header.id;
+  new->mask = al->mask;
+
+  if (!IS_EXTERNAL_METRIC (al->e[0].tos))
+    {
+      zlog_info ("Route[External]: type-1 created.");
+      new->path_type = OSPF_PATH_TYPE1_EXTERNAL;
+      new->cost = asbr_route->cost + metric;		/* X + Y */
+    }
+  else
+    {
+      zlog_info ("Route[External]: type-2 created.");
+      new->path_type = OSPF_PATH_TYPE2_EXTERNAL;
+      new->cost = asbr_route->cost;			/* X */
+      new->u.ext.type2_cost = metric;			/* Y */
+    }
+
+  new->type = OSPF_DESTINATION_NETWORK;
+  new->path = list_new ();
+  new->u.ext.origin = lsa;
+  new->u.ext.tag = ntohl (al->e[0].route_tag);
+  new->u.ext.asbr = asbr_route;
+
+  assert (new != asbr_route);
+
+  return new;
+}
+
+#define OSPF_ASE_CALC_INTERVAL 1
+
+int
+ospf_ase_calculate_route (struct ospf_lsa * lsa, void * p_arg, int n_arg)
+{
+  u_int32_t metric;
+  struct as_external_lsa *al;
+  struct ospf_route *asbr_route;
+  struct prefix_ipv4 asbr, p;
+  struct route_node *rn;
+  struct ospf_route *new, *or;
+  int ret;
+  
+  assert (lsa);
+  al = (struct as_external_lsa *) lsa->data;
+
+#ifdef HAVE_NSSA
+  if (lsa->data->type == OSPF_AS_NSSA_LSA)
+    if (IS_DEBUG_OSPF_NSSA)
+      zlog_info ("ospf_ase_calc(): Processing Type-7");
+
+  /* Stay away from any Local Translated Type-7 LSAs */
+  if (CHECK_FLAG (lsa->flags, OSPF_LSA_LOCAL_XLT))
+    {
+      if (IS_DEBUG_OSPF_NSSA)
+	zlog_info ("ospf_ase_calc(): Rejecting Local Xlt'd");
+      return 0;
+    }
+#endif /* HAVE_NSSA */
+
+  zlog_info ("Route[External]: Calculate AS-external-LSA to %s/%d",
+	     inet_ntoa (al->header.id), ip_masklen (al->mask));
+  /* (1) If the cost specified by the LSA is LSInfinity, or if the
+         LSA's LS age is equal to MaxAge, then examine the next LSA. */
+  if ((metric = GET_METRIC (al->e[0].metric)) >= OSPF_LS_INFINITY)
+    {
+      zlog_info ("Route[External]: Metric is OSPF_LS_INFINITY");
+      return 0;
+    }
+  if (IS_LSA_MAXAGE (lsa))
+    {
+      zlog_info ("Route[External]: AS-external-LSA is MAXAGE");
+      return 0;
+    }
+  
+  /* (2) If the LSA was originated by the calculating router itself,
+     examine the next LSA. */
+  if (IS_LSA_SELF (lsa))
+    {
+      zlog_info ("Route[External]: AS-external-LSA is self originated");
+      return 0;
+    }
+
+  /* (3) Call the destination described by the LSA N.  N's address is
+         obtained by masking the LSA's Link State ID with the
+	 network/subnet mask contained in the body of the LSA.  Look
+	 up the routing table entries (potentially one per attached
+	 area) for the AS boundary router (ASBR) that originated the
+	 LSA. If no entries exist for router ASBR (i.e., ASBR is
+	 unreachable), do nothing with this LSA and consider the next
+	 in the list. */
+  
+  asbr.family = AF_INET;
+  asbr.prefix = al->header.adv_router;
+  asbr.prefixlen = IPV4_MAX_BITLEN;
+  apply_mask_ipv4 (&asbr);
+  
+  asbr_route = ospf_find_asbr_route (ospf_top->new_rtrs, &asbr);
+  if (asbr_route == NULL)
+    {
+      zlog_info ("Route[External]: Can't find originating ASBR route");
+      return 0;
+    }
+  if (!(asbr_route->u.std.flags & ROUTER_LSA_EXTERNAL))
+    {
+      zlog_info ("Route[External]: Originating router is not an ASBR");
+      return 0;
+    }
+  
+  /*     Else, this LSA describes an AS external path to destination
+	 N.  Examine the forwarding address specified in the AS-
+	 external-LSA.  This indicates the IP address to which
+	 packets for the destination should be forwarded. */
+  
+  if (al->e[0].fwd_addr.s_addr == 0)
+    {
+      /* If the forwarding address is set to 0.0.0.0, packets should
+	 be sent to the ASBR itself. Among the multiple routing table
+	 entries for the ASBR, select the preferred entry as follows.
+	 If RFC1583Compatibility is set to "disabled", prune the set
+	 of routing table entries for the ASBR as described in
+	 Section 16.4.1. In any case, among the remaining routing
+	 table entries, select the routing table entry with the least
+	 cost; when there are multiple least cost routing table
+	 entries the entry whose associated area has the largest OSPF
+	 Area ID (when considered as an unsigned 32-bit integer) is
+	 chosen. */
+
+      /* asbr_route already contains the requested route */
+    }
+  else
+    {
+      /* If the forwarding address is non-zero, look up the
+	 forwarding address in the routing table.[24] The matching
+	 routing table entry must specify an intra-area or inter-area
+	 path; if no such path exists, do nothing with the LSA and
+	 consider the next in the list. */
+      if (! ospf_ase_forward_address_check (al->e[0].fwd_addr))
+	{
+	  zlog_info ("Route[External]: Forwarding address is our router address");
+	  return 0;
+	}
+      
+      asbr.family = AF_INET;
+      asbr.prefix = al->e[0].fwd_addr;
+      asbr.prefixlen = IPV4_MAX_BITLEN;
+
+      rn = route_node_match (ospf_top->new_table, (struct prefix *) &asbr);
+      
+      if (rn == NULL || (asbr_route = rn->info) == NULL)
+	{
+	  zlog_info ("Route[External]: Can't find route to forwarding address");
+	  if (rn)
+	    route_unlock_node (rn);
+	  return 0;
+	}
+
+      route_unlock_node (rn);
+    }
+
+  /* (4) Let X be the cost specified by the preferred routing table
+         entry for the ASBR/forwarding address, and Y the cost
+	 specified in the LSA.  X is in terms of the link state
+	 metric, and Y is a type 1 or 2 external metric. */
+			 
+
+  /* (5) Look up the routing table entry for the destination N.  If
+         no entry exists for N, install the AS external path to N,
+	 with next hop equal to the list of next hops to the
+	 forwarding address, and advertising router equal to ASBR.
+	 If the external metric type is 1, then the path-type is set
+	 to type 1 external and the cost is equal to X+Y.  If the
+	 external metric type is 2, the path-type is set to type 2
+	 external, the link state component of the route's cost is X,
+	 and the type 2 cost is Y. */
+  new = ospf_ase_calculate_new_route (lsa, asbr_route, metric);
+
+  /* (6) Compare the AS external path described by the LSA with the
+         existing paths in N's routing table entry, as follows. If
+	 the new path is preferred, it replaces the present paths in
+	 N's routing table entry.  If the new path is of equal
+	 preference, it is added to N's routing table entry's list of
+	 paths. */
+
+  /* Set prefix. */
+  p.family = AF_INET;
+  p.prefix = al->header.id;
+  p.prefixlen = ip_masklen (al->mask);
+
+  /* if there is a Intra/Inter area route to the N
+     do not install external route */
+  if ((rn = route_node_lookup (ospf_top->new_table,
+			       (struct prefix *) &p)) != NULL
+      && (rn->info != NULL))
+    {
+      if (new)
+	ospf_route_free (new);
+      return 0;
+    }
+  
+  /* Find a route to the same dest */
+  /* If there is no route, create new one. */
+  if ((rn = route_node_lookup (ospf_top->new_external_route,
+			       (struct prefix *) &p)) == NULL 
+      || (or = rn->info) == NULL)
+    {
+      zlog_info ("Route[External]: Adding a new route %s/%d",
+		 inet_ntoa (p.prefix), p.prefixlen);
+
+      ospf_route_add (ospf_top->new_external_route, &p, new, asbr_route);
+
+      if (al->e[0].fwd_addr.s_addr)
+	ospf_ase_complete_direct_routes (new, al->e[0].fwd_addr);
+      return 0;
+    }
+  else
+    {
+      /* (a) Intra-area and inter-area paths are always preferred
+             over AS external paths.
+
+         (b) Type 1 external paths are always preferred over type 2
+             external paths. When all paths are type 2 external
+	     paths, the paths with the smallest advertised type 2
+	     metric are always preferred. */
+      ret = ospf_route_cmp (new, or);
+  
+  /*     (c) If the new AS external path is still indistinguishable
+             from the current paths in the N's routing table entry,
+	     and RFC1583Compatibility is set to "disabled", select
+	     the preferred paths based on the intra-AS paths to the
+	     ASBR/forwarding addresses, as specified in Section
+	     16.4.1.
+
+         (d) If the new AS external path is still indistinguishable
+             from the current paths in the N's routing table entry,
+	     select the preferred path based on a least cost
+	     comparison.  Type 1 external paths are compared by
+	     looking at the sum of the distance to the forwarding
+	     address and the advertised type 1 metric (X+Y).  Type 2
+	     external paths advertising equal type 2 metrics are
+	     compared by looking at the distance to the forwarding
+	     addresses.
+  */
+      /* New route is better */
+      if (ret < 0)
+	{
+	  zlog_info ("Route[External]: New route is better");
+	  ospf_route_subst (rn, new, asbr_route);
+	  if (al->e[0].fwd_addr.s_addr)
+	    ospf_ase_complete_direct_routes (new, al->e[0].fwd_addr);
+	  or = new;
+	  new = NULL;
+	}
+      /* Old route is better */
+      else if (ret > 0)
+	{
+	  zlog_info ("Route[External]: Old route is better");
+	  /* do nothing */
+	}
+      /* Routes are equal */
+      else
+	{
+	  zlog_info ("Route[External]: Routes are equal");
+	  ospf_route_copy_nexthops (or, asbr_route->path);
+	  if (al->e[0].fwd_addr.s_addr)
+	    ospf_ase_complete_direct_routes (or, al->e[0].fwd_addr);
+	}
+    }
+  /* Make sure setting newly calculated ASBR route.*/
+  or->u.ext.asbr = asbr_route;
+  if (new)
+    ospf_route_free (new);
+
+  lsa->route = or;
+  return 0;
+}
+
+int
+ospf_ase_route_match_same (struct route_table *rt, struct prefix *prefix,
+			   struct ospf_route *newor)
+{
+  struct route_node *rn;
+  struct ospf_route *or;
+  struct ospf_path *op;
+  struct ospf_path *newop;
+  listnode n1;
+  listnode n2;
+
+  if (! rt || ! prefix)
+    return 0;
+
+   rn = route_node_lookup (rt, prefix);
+   if (! rn)
+     return 0;
+ 
+   route_unlock_node (rn);
+
+   or = rn->info;
+   if (or->path_type != newor->path_type)
+     return 0;
+
+   switch (or->path_type)
+     {
+     case OSPF_PATH_TYPE1_EXTERNAL:
+       if (or->cost != newor->cost)
+	 return 0;
+       break;
+     case OSPF_PATH_TYPE2_EXTERNAL:
+       if ((or->cost != newor->cost) ||
+	   (or->u.ext.type2_cost != newor->u.ext.type2_cost))
+	 return 0;
+       break;
+     default:
+       assert (0);
+       return 0;
+     }
+   
+   if (or->path->count != newor->path->count)
+     return 0;
+       
+   /* Check each path. */
+   for (n1 = listhead (or->path), n2 = listhead (newor->path);
+	n1 && n2; nextnode (n1), nextnode (n2))
+     { 
+       op = getdata (n1);
+       newop = getdata (n2);
+       
+       if (! IPV4_ADDR_SAME (&op->nexthop, &newop->nexthop))
+	 return 0;
+     }
+   return 1;
+}
+
+int
+ospf_ase_compare_tables (struct route_table *new_external_route,
+			 struct route_table *old_external_route)
+{
+  struct route_node *rn, *new_rn;
+  struct ospf_route *or;
+  
+  /* Remove deleted routes */
+  for (rn = route_top (old_external_route); rn; rn = route_next (rn))
+    if ((or = rn->info))
+      {
+	if (! (new_rn = route_node_lookup (new_external_route, &rn->p)))
+	  ospf_zebra_delete ((struct prefix_ipv4 *) &rn->p, or);
+	else
+	  route_unlock_node (new_rn);
+      }
+  
+	
+  /* Install new routes */
+  for (rn = route_top (new_external_route); rn; rn = route_next (rn))
+    if ((or = rn->info) != NULL)
+      if (! ospf_ase_route_match_same (old_external_route, &rn->p, or))
+	ospf_zebra_add ((struct prefix_ipv4 *) &rn->p, or);
+				       
+  return 0;
+}
+
+int
+ospf_ase_calculate_timer (struct thread *t)
+{
+  struct ospf *ospf;
+
+#ifdef HAVE_NSSA
+      listnode node;
+      struct ospf_area *area;
+#endif /* HAVE_NSSA */
+
+  ospf = THREAD_ARG (t);
+  ospf->t_ase_calc = NULL;
+
+  if (ospf->ase_calc)
+    {
+      ospf->ase_calc = 0;
+
+      /* Calculate external route for each AS-external-LSA */
+      foreach_lsa (EXTERNAL_LSDB (ospf_top), NULL, 0,
+		   ospf_ase_calculate_route);
+
+#ifdef HAVE_NSSA
+      /*  This version simple adds to the table all NSSA areas  */
+      if (ospf_top->anyNSSA)
+	for (node = listhead (ospf_top->areas); node; nextnode (node))
+	  {
+	    area = getdata (node);
+	    if (IS_DEBUG_OSPF_NSSA)
+	      zlog_info ("ospf_ase_calculate_timer(): looking at area %s",
+			 inet_ntoa (area->area_id));
+
+	    if (area->external_routing == OSPF_AREA_NSSA)
+
+	      foreach_lsa (NSSA_LSDB (area), NULL, 0,
+			   ospf_ase_calculate_route);
+	  }
+#endif /* HAVE_NSSA */
+
+      /* Compare old and new external routing table and install the
+	 difference info zebra/kernel */
+      ospf_ase_compare_tables (ospf_top->new_external_route,
+			       ospf_top->old_external_route);
+
+      /* Delete old external routing table */
+      ospf_route_table_free (ospf_top->old_external_route);
+      ospf_top->old_external_route = ospf_top->new_external_route;
+      ospf_top->new_external_route = route_table_init ();
+    }
+  return 0;
+}
+
+void
+ospf_ase_calculate_schedule ()
+{
+  if (! ospf_top)
+    return;
+
+  ospf_top->ase_calc = 1;
+}
+
+void
+ospf_ase_calculate_timer_add ()
+{
+  if (! ospf_top)
+    return;
+
+  if (! ospf_top->t_ase_calc)
+    ospf_top->t_ase_calc = thread_add_timer (master, ospf_ase_calculate_timer,
+					     ospf_top, OSPF_ASE_CALC_INTERVAL);
+}
+
+void
+ospf_ase_register_external_lsa (struct ospf_lsa *lsa, struct ospf *top)
+{
+  struct route_node *rn;
+  struct prefix_ipv4 p;
+  list lst;
+  struct as_external_lsa *al;
+
+  al = (struct as_external_lsa *) lsa->data;
+  p.family = AF_INET;
+  p.prefix = lsa->data->id;
+  p.prefixlen = ip_masklen (al->mask);
+  apply_mask_ipv4 (&p);
+
+  rn = route_node_get (top->external_lsas, (struct prefix *) &p);
+  if ((lst = rn->info) == NULL)
+    rn->info = lst = list_new();
+
+  /* We assume that if LSA is deleted from DB
+     is is also deleted from this RT */
+
+  listnode_add (lst, ospf_lsa_lock (lsa));
+}
+
+void
+ospf_ase_unregister_external_lsa (struct ospf_lsa *lsa, struct ospf *top)
+{
+  struct route_node *rn;
+  struct prefix_ipv4 p;
+  list lst;
+  struct as_external_lsa *al;
+
+  al = (struct as_external_lsa *) lsa->data;
+  p.family = AF_INET;
+  p.prefix = lsa->data->id;
+  p.prefixlen = ip_masklen (al->mask);
+  apply_mask_ipv4 (&p);
+
+  rn = route_node_get (top->external_lsas, (struct prefix *) &p);
+  lst = rn->info;
+#ifdef ORIGINAL_CODING
+  assert (lst);
+
+  listnode_delete (lst, lsa);
+  ospf_lsa_unlock (lsa);
+#else /* ORIGINAL_CODING */
+  /* XXX lst can be NULL */
+  if (lst) {
+    listnode_delete (lst, lsa);
+    ospf_lsa_unlock (lsa);
+  }
+#endif /* ORIGINAL_CODING */
+}
+
+void
+ospf_ase_external_lsas_finish (struct route_table *rt)
+{
+  struct route_node *rn;
+  struct ospf_lsa *lsa;
+  list lst;
+  listnode node;
+  
+  for (rn = route_top (rt); rn; rn = route_next (rn))
+    if ((lst = rn->info) != NULL)
+      {
+	for (node = listhead (lst); node; node = nextnode (node))
+	  if ((lsa = getdata (node)) != NULL)
+	    ospf_lsa_unlock (lsa);
+	list_delete (lst);
+      }
+  
+  route_table_finish (rt);
+}
+
+void
+ospf_ase_incremental_update (struct ospf_lsa *lsa, struct ospf *top)
+{
+  list lsas;
+  listnode node;
+  struct route_node *rn, *rn2;
+  struct prefix_ipv4 p;
+  struct route_table *tmp_old;
+  struct as_external_lsa *al;
+
+  al = (struct as_external_lsa *) lsa->data;
+  p.family = AF_INET;
+  p.prefix = lsa->data->id;
+  p.prefixlen = ip_masklen (al->mask);
+  apply_mask_ipv4 (&p);
+
+  /* if new_table is NULL, there was no spf calculation, thus
+     incremental update is unneeded */
+  if (!top->new_table)
+    return;
+  
+  /* If there is already an intra-area or inter-area route
+     to the destination, no recalculation is necessary
+     (internal routes take precedence). */
+  
+  rn = route_node_lookup (top->new_table, (struct prefix *) &p);
+  if (rn && rn->info)
+    {
+      route_unlock_node (rn);
+      return;
+    }
+
+  rn = route_node_lookup (top->external_lsas, (struct prefix *) &p);
+  assert (rn && rn->info);
+  lsas = rn->info;
+  
+  for (node = listhead (lsas); node; nextnode (node))
+    if ((lsa = getdata (node)) != NULL)
+      ospf_ase_calculate_route (lsa, NULL, 0);
+
+  /* prepare temporary old routing table for compare */
+  tmp_old = route_table_init ();
+  rn = route_node_lookup (top->old_external_route, (struct prefix *) &p);
+  if (rn && rn->info)
+    {
+      rn2 = route_node_get (tmp_old, (struct prefix *) &p);
+      rn2->info = rn->info;
+    }
+
+  /* install changes to zebra */
+  ospf_ase_compare_tables (top->new_external_route, tmp_old);
+
+  /* update top->old_external_route table */
+  if (rn && rn->info)
+    ospf_route_free ((struct ospf_route *) rn->info);
+
+  rn2 = route_node_lookup (top->new_external_route, (struct prefix *) &p);
+  /* if new route exists, install it to top->old_external_route */
+  if (rn2 && rn2->info)
+    {
+      if (!rn)
+	rn = route_node_get (top->old_external_route, (struct prefix *) &p);
+      rn->info = rn2->info;
+    }
+  else
+    {
+      /* remove route node from top->old_external_route */
+      if (rn)
+	{
+	  rn->info = NULL;
+	  route_unlock_node (rn);
+	  route_unlock_node (rn);
+	}
+    }
+
+  if (rn2)
+    {
+      /* rn2->info is stored in route node of top->old_external_route */
+      rn2->info = NULL;
+      route_unlock_node (rn2);
+      route_unlock_node (rn2);
+    }
+
+  route_table_finish (tmp_old);
+}