diff --git a/filter/filter.c b/filter/filter.c
index 5c0e62f9..7a5ba5b9 100644
--- a/filter/filter.c
+++ b/filter/filter.c
@@ -1095,11 +1095,11 @@ interpret(struct f_inst *what)
       runtime( "Integer expected");
     if (v1.type != T_IP)
       runtime( "You can mask only IP addresses" );
-    {
-      ip_addr mask = ipa_mkmask(v2.val.i);
-      res.type = T_IP;
-      res.val.ip = ipa_and(mask, v1.val.ip);
-    }
+
+    res.type = T_IP;
+    res.val.ip = ipa_is_ip4(v1.val.ip) ?
+      ipa_from_ip4(ip4_and(ipa_to_ip4(v1.val.ip), ip4_mkmask(v2.val.i))) :
+      ipa_from_ip6(ip6_and(ipa_to_ip6(v1.val.ip), ip6_mkmask(v2.val.i)));
     break;
 
   case 'E':	/* Create empty attribute */
diff --git a/filter/filter.h b/filter/filter.h
index fe753630..1052f8c8 100644
--- a/filter/filter.h
+++ b/filter/filter.h
@@ -76,7 +76,7 @@ int same_tree(struct f_tree *t1, struct f_tree *t2);
 void tree_format(struct f_tree *t, buffer *buf);
 
 struct f_trie *f_new_trie(linpool *lp, uint node_size);
-void *trie_add_prefix(struct f_trie *t, net_addr *n, uint l, uint h);
+void *trie_add_prefix(struct f_trie *t, const net_addr *n, uint l, uint h);
 int trie_match_net(struct f_trie *t, const net_addr *n);
 int trie_same(struct f_trie *t1, struct f_trie *t2);
 void trie_format(struct f_trie *t, buffer *buf);
diff --git a/filter/trie.c b/filter/trie.c
index 9fdaac6d..6e234af4 100644
--- a/filter/trie.c
+++ b/filter/trie.c
@@ -74,6 +74,19 @@
 #include "conf/conf.h"
 #include "filter/filter.h"
 
+
+/*
+ * In the trie code, the prefix length is internally treated as for the whole
+ * ip_addr, regardless whether it contains an IPv4 or IPv6 address. Therefore,
+ * remaining definitions make sense.
+ */
+
+#define ipa_mkmask(x) ip6_mkmask(x)
+#define ipa_masklen(x) ip6_masklen(&x)
+#define ipa_pxlen(x,y) ip6_pxlen(x,y)
+#define ipa_getbit(x,n) ip6_getbit(x,n)
+
+
 /**
  * f_new_trie - allocates and returns a new empty trie
  * @lp: linear pool to allocate items from
@@ -123,7 +136,7 @@ attach_node(struct f_trie_node *parent, struct f_trie_node *child)
  */
 
 void *
-trie_add_prefix(struct f_trie *t, net_addr *net, uint l, uint h)
+trie_add_prefix(struct f_trie *t, const net_addr *net, uint l, uint h)
 {
   ip_addr px = net_prefix(net);
   uint plen = net_pxlen(net);
diff --git a/lib/birdlib.h b/lib/birdlib.h
index 5fec6c7a..9ffe0070 100644
--- a/lib/birdlib.h
+++ b/lib/birdlib.h
@@ -55,12 +55,6 @@ static inline int u64_cmp(u64 i1, u64 i2)
 #define NULL ((void *) 0)
 #endif
 
-#ifndef IPV6
-#define IP_VERSION 4
-#else
-#define IP_VERSION 6
-#endif
-
 
 /* Macros for gcc attributes */
 
diff --git a/lib/ip.h b/lib/ip.h
index 7a31dad0..60a9a7b2 100644
--- a/lib/ip.h
+++ b/lib/ip.h
@@ -77,8 +77,6 @@ typedef struct ip6_addr {
 #define _I3(a) ((a).addr[3])
 
 
-#ifdef IPV6
-
 /* Structure ip_addr may contain both IPv4 and IPv6 addresses */
 typedef ip6_addr ip_addr;
 #define IPA_NONE IP6_NONE
@@ -93,24 +91,6 @@ typedef ip6_addr ip_addr;
 
 #define ipa_is_ip4(a) ip6_is_v4mapped(a)
 
-#else
-
-/* Provisionary ip_addr definition same as ip4_addr */
-typedef ip4_addr ip_addr;
-#define IPA_NONE IP4_NONE
-
-#define ipa_from_ip4(x) x
-#define ipa_from_ip6(x) IPA_NONE
-#define ipa_from_u32(x) ipa_from_ip4(ip4_from_u32(x))
-
-#define ipa_to_ip4(x) x
-#define ipa_to_ip6(x) IP6_NONE
-#define ipa_to_u32(x) ip4_to_u32(ipa_to_ip4(x))
-
-#define ipa_is_ip4(a) 1
-
-#endif
-
 
 /*
  *	Public constructors
@@ -174,7 +154,6 @@ static inline ip6_addr ip6_not(ip6_addr a)
 { return _MI6(~_I0(a), ~_I1(a), ~_I2(a), ~_I3(a)); }
 
 
-#ifdef IPV6
 #define ipa_equal(x,y) ip6_equal(x,y)
 #define ipa_zero(x) ip6_zero(x)
 #define ipa_nonzero(x) ip6_nonzero(x)
@@ -182,19 +161,8 @@ static inline ip6_addr ip6_not(ip6_addr a)
 #define ipa_or(x,y) ip6_or(x,y)
 #define ipa_xor(x,y) ip6_xor(x,y)
 #define ipa_not(x) ip6_not(x)
-#else
-#define ipa_equal(x,y) ip4_equal(x,y)
-#define ipa_zero(x) ip4_zero(x)
-#define ipa_nonzero(x) ip4_nonzero(x)
-#define ipa_and(x,y) ip4_and(x,y)
-#define ipa_or(x,y) ip4_or(x,y)
-#define ipa_xor(x,y) ip4_xor(x,y)
-#define ipa_not(x) ip4_not(x)
-#endif
 
 
-
-#ifdef IPV6
 /*
  * A zero address is either a token for invalid/unused, or the prefix of default
  * routes. These functions should be used in the second case, where both IPv4
@@ -207,11 +175,6 @@ static inline int ipa_zero2(ip_addr a)
 static inline int ipa_nonzero2(ip_addr a)
 { return _I0(a) || _I1(a) || ((_I2(a) != 0) && (_I2(a) != 0xffff)) || _I3(a); }
 
-#else
-#define ipa_zero2(x) ip4_zero(x)
-#define ipa_nonzero2(x) ip4_nonzero(x)
-#endif
-
 
 /*
  *	Hash and compare functions
@@ -254,16 +217,9 @@ static inline int ip4_compare(ip4_addr a, ip4_addr b)
 
 int ip6_compare(ip6_addr a, ip6_addr b);
 
-
-#ifdef IPV6
 #define ipa_hash(x) ip6_hash(x)
 #define ipa_hash32(x) ip6_hash32(x)
 #define ipa_compare(x,y) ip6_compare(x,y)
-#else
-#define ipa_hash(x) ip4_hash(x)
-#define ipa_hash32(x) ip4_hash32(x)
-#define ipa_compare(x,y) ip4_compare(x,y)
-#endif
 
 
 /*
@@ -294,14 +250,10 @@ static inline int ip6_is_link_local(ip6_addr a)
 static inline int ip6_is_v4mapped(ip6_addr a)
 { return _I0(a) == 0 && _I1(a) == 0 && _I2(a) == 0xffff; }
 
-#ifdef IPV6
 #define ipa_classify(x) ip6_classify(&(x))
 #define ipa_is_link_local(x) ip6_is_link_local(x)
-#else
-#define ipa_classify(x) ip4_classify(x)
-#define ipa_is_link_local(x) 0
-#endif
 
+/* XXXX remove */
 static inline int ipa_classify_net(ip_addr a)
 { return ipa_zero2(a) ? (IADDR_HOST | SCOPE_UNIVERSE) : ipa_classify(a); }
 
@@ -365,25 +317,8 @@ static inline ip6_addr ip6_opposite_m2(ip6_addr a)
 
 ip4_addr ip4_class_mask(ip4_addr ad);
 
-#ifdef IPV6
-#define ipa_mkmask(x) ip6_mkmask(x)
-#define ipa_masklen(x) ip6_masklen(&x)
-#define ipa_pxlen(x,y) ip6_pxlen(x,y)
-#define ipa_getbit(x,n) ip6_getbit(x,n)
-#define ipa_setbit(x,n) ip6_setbit(x,n)
-#define ipa_clrbit(x,n) ip6_clrbit(x,n)
 #define ipa_opposite_m1(x) ip6_opposite_m1(x)
 #define ipa_opposite_m2(x) ip6_opposite_m2(x)
-#else
-#define ipa_mkmask(x) ip4_mkmask(x)
-#define ipa_masklen(x) ip4_masklen(x)
-#define ipa_pxlen(x,y) ip4_pxlen(x,y)
-#define ipa_getbit(x,n) ip4_getbit(x,n)
-#define ipa_setbit(x,n) ip4_setbit(x,n)
-#define ipa_clrbit(x,n) ip4_clrbit(x,n)
-#define ipa_opposite_m1(x) ip4_opposite_m1(x)
-#define ipa_opposite_m2(x) ip4_opposite_m2(x)
-#endif
 
 
 /*
@@ -402,14 +337,6 @@ static inline ip6_addr ip6_hton(ip6_addr a)
 static inline ip6_addr ip6_ntoh(ip6_addr a)
 { return _MI6(ntohl(_I0(a)), ntohl(_I1(a)), ntohl(_I2(a)), ntohl(_I3(a))); }
 
-#ifdef IPV6
-#define ipa_hton(x) x = ip6_hton(x)
-#define ipa_ntoh(x) x = ip6_ntoh(x)
-#else
-#define ipa_hton(x) x = ip4_hton(x)
-#define ipa_ntoh(x) x = ip4_ntoh(x)
-#endif
-
 
 /*
  *	Unaligned data access (in network order)
@@ -440,15 +367,6 @@ static inline void * put_ip6(void *buf, ip6_addr a)
   return buf+16;
 }
 
-// XXXX these functions must be redesigned or removed
-#ifdef IPV6
-#define get_ipa(x) get_ip6(x)
-#define put_ipa(x,y) put_ip6(x,y)
-#else
-#define get_ipa(x) get_ip4(x)
-#define put_ipa(x,y) put_ip4(x,y)
-#endif
-
 
 /*
  *	Binary/text form conversions
@@ -466,28 +384,11 @@ static inline char * ip6_ntox(ip6_addr a, char *b)
 int ip4_pton(const char *a, ip4_addr *o);
 int ip6_pton(const char *a, ip6_addr *o);
 
-// XXXX these functions must be redesigned or removed
-#ifdef IPV6
-#define ipa_ntop(x,y) ip6_ntop(x,y)
-#define ipa_ntox(x,y) ip6_ntox(x,y)
-#define ipa_pton(x,y) ip6_pton(x,y)
-#else
-#define ipa_ntop(x,y) ip4_ntop(x,y)
-#define ipa_ntox(x,y) ip4_ntox(x,y)
-#define ipa_pton(x,y) ip4_pton(x,y)
-#endif
-
 
 /*
  *	Miscellaneous
  */
 
-// XXXX review this
-
-#define ip_is_prefix(a,l) (!ipa_nonzero(ipa_and(a, ipa_not(ipa_mkmask(l)))))
-#define ipa_in_net(x,n,p) (ipa_zero(ipa_and(ipa_xor((n),(x)),ipa_mkmask(p))))
-#define net_in_net(n1,l1,n2,l2) (((l1) >= (l2)) && (ipa_zero(ipa_and(ipa_xor((n1),(n2)),ipa_mkmask(l2)))))
-
 char *ip_scope_text(uint);
 
 #endif
diff --git a/lib/net.c b/lib/net.c
index 09f23c7a..76ecd460 100644
--- a/lib/net.c
+++ b/lib/net.c
@@ -136,33 +136,36 @@ net_classify(const net_addr *N)
     return ip6_zero(n->ip6.prefix) ? (IADDR_HOST | SCOPE_UNIVERSE) : ip6_classify(&n->ip6.prefix);
   }
 
-  return 0;
+  return IADDR_INVALID;
 }
 
 int
-ipa_in_netX(const ip_addr A, const net_addr *N)
+ipa_in_netX(const ip_addr a, const net_addr *n)
 {
-  switch (N->type)
+  switch (n->type)
   {
   case NET_IP4:
   case NET_VPN4:
-    if (!ipa_is_ip4(A)) return 0;
-    break;
+    if (!ipa_is_ip4(a)) return 0;
+    return ip4_zero(ip4_and(ip4_xor(ipa_to_ip4(a), net4_prefix(n)),
+			    ip4_mkmask(net4_pxlen(n))));
 
   case NET_IP6:
   case NET_VPN6:
-    if (ipa_is_ip4(A)) return 0;
-    break;
-  }
+    if (ipa_is_ip4(a)) return 0;
+    return ip6_zero(ip6_and(ip6_xor(ipa_to_ip6(a), net6_prefix(n)),
+			    ip6_mkmask(net6_pxlen(n))));
 
-  return ipa_zero(ipa_and(ipa_xor(A, net_prefix(N)), ipa_mkmask(net_pxlen(N))));
+  default:
+    return 0;
+  }
 }
 
 int
-net_in_netX(const net_addr *A, const net_addr *N)
+net_in_netX(const net_addr *a, const net_addr *n)
 {
-  if (A->type != N->type)
+  if (a->type != n->type)
     return 0;
 
-  return (net_pxlen(N) <= net_pxlen(A)) && ipa_in_netX(net_prefix(A), N);
+  return (net_pxlen(n) <= net_pxlen(a)) && ipa_in_netX(net_prefix(a), n);
 }
diff --git a/nest/config.Y b/nest/config.Y
index de75509f..9d20dd48 100644
--- a/nest/config.Y
+++ b/nest/config.Y
@@ -55,7 +55,7 @@ CF_DECLS
 
 CF_KEYWORDS(ROUTER, ID, PROTOCOL, TEMPLATE, PREFERENCE, DISABLED, DEBUG, ALL, OFF, DIRECT)
 CF_KEYWORDS(INTERFACE, IMPORT, EXPORT, FILTER, NONE, TABLE, STATES, ROUTES, FILTERS)
-CF_KEYWORDS(IPV4, IPVX, VPN4, VPN6)
+CF_KEYWORDS(IPV4, IPV6, VPN4, VPN6)
 CF_KEYWORDS(RECEIVE, LIMIT, ACTION, WARN, BLOCK, RESTART, DISABLE, KEEP, FILTERED)
 CF_KEYWORDS(PASSWORD, FROM, PASSIVE, TO, ID, EVENTS, PACKETS, PROTOCOLS, INTERFACES)
 CF_KEYWORDS(PRIMARY, STATS, COUNT, FOR, COMMANDS, PREEXPORT, NOEXPORT, GENERATE) /* ,ROA */
@@ -134,7 +134,7 @@ CF_ADDTO(conf, table)
 table_type:
    /* empty */ { $$ = NET_IP4; }
  | IPV4 { $$ = NET_IP4; }
- | IPVX { $$ = NET_IP6; } /* XXXX */
+ | IPV6 { $$ = NET_IP6; }
  | VPN4 { $$ = NET_VPN4; }
  | VPN6 { $$ = NET_VPN6; }
  ;
diff --git a/proto/ospf/config.Y b/proto/ospf/config.Y
index 6d8fa755..5673ef60 100644
--- a/proto/ospf/config.Y
+++ b/proto/ospf/config.Y
@@ -316,7 +316,6 @@ ospf_iface_item:
  | TTL SECURITY bool { OSPF_PATT->ttl_security = $3; }
  | TTL SECURITY TX ONLY { OSPF_PATT->ttl_security = 2; }
  | BFD bool { OSPF_PATT->bfd = $2; cf_check_bfd($2); }
- | SECONDARY bool { OSPF_PATT->bsd_secondary = $2; }
  | password_list { ospf_check_auth(); }
  ;
 
diff --git a/proto/ospf/iface.c b/proto/ospf/iface.c
index 91e22266..442cec3a 100644
--- a/proto/ospf/iface.c
+++ b/proto/ospf/iface.c
@@ -525,15 +525,6 @@ ospf_iface_stubby(struct ospf_iface_patt *ip, struct ifa *addr)
   if (addr->iface->flags & IF_LOOPBACK)
     return 1;
 
-  /*
-   * For compatibility reasons on BSD systems, we force OSPF
-   * interfaces with non-primary IP prefixes to be stub.
-   */
-#if defined(OSPFv2) && !defined(CONFIG_MC_PROPER_SRC)
-  if (!ip->bsd_secondary && !(addr->flags & IA_PRIMARY))
-    return 1;
-#endif
-
   return ip->stub;
 }
 
diff --git a/proto/ospf/ospf.h b/proto/ospf/ospf.h
index f4f91de1..b1e02b24 100644
--- a/proto/ospf/ospf.h
+++ b/proto/ospf/ospf.h
@@ -185,7 +185,6 @@ struct ospf_iface_patt
   u8 ptp_netmask;		/* bool + 2 for unspecified */
   u8 ttl_security;		/* bool + 2 for TX only */
   u8 bfd;
-  u8 bsd_secondary;
   list *passwords;
 };
 
diff --git a/sysdep/bsd/krt-sock.c b/sysdep/bsd/krt-sock.c
index 19e82047..dd62b375 100644
--- a/sysdep/bsd/krt-sock.c
+++ b/sysdep/bsd/krt-sock.c
@@ -71,6 +71,7 @@
 #define KRT_MAX_TABLES 1
 #endif
 
+#define IPV6 1
 
 
 /* Dynamic max number of tables */
diff --git a/sysdep/config.h b/sysdep/config.h
index 9620a37d..08c15fe9 100644
--- a/sysdep/config.h
+++ b/sysdep/config.h
@@ -9,9 +9,6 @@
 /* BIRD version */
 #define BIRD_VERSION "1.5.0"
 
-/* XXXX Temporary */
-#define IPV6 1
-
 /* Include parameters determined by configure script */
 #include "sysdep/autoconf.h"
 
diff --git a/sysdep/linux/netlink.c b/sysdep/linux/netlink.c
index b3d0a9ab..201d074e 100644
--- a/sysdep/linux/netlink.c
+++ b/sysdep/linux/netlink.c
@@ -1169,7 +1169,8 @@ nl_parse_route(struct nlmsghdr *h, int scan)
 	  ra.gw = rta_get_ipa(a[RTA_GATEWAY]);
 
 	  /* Silently skip strange 6to4 routes */
-	  if ((i->rtm_family == AF_INET6) && ipa_in_net(ra.gw, IPA_NONE, 96))
+	  const net_addr_ip6 sit = NET_ADDR_IP6(IP6_NONE, 96);
+	  if ((i->rtm_family == AF_INET6) && ipa_in_netX(ra.gw, (net_addr *) &sit))
 	    return;
 
 	  neighbor *nbr;
diff --git a/sysdep/unix/krt.Y b/sysdep/unix/krt.Y
index e769ec0f..eb0ae109 100644
--- a/sysdep/unix/krt.Y
+++ b/sysdep/unix/krt.Y
@@ -69,8 +69,7 @@ kif_item:
    }
  | PRIMARY opttext net_or_ipa {
      struct kif_primary_item *kpi = cfg_alloc(sizeof (struct kif_primary_item));
-     kpi->prefix = IPA_NONE; /* XXXX */
-     kpi->pxlen = 0; /* XXXX */
+     kpi->addr = $3.n;
      add_tail(&THIS_KIF->primary, &kpi->n);
    }
  ;
diff --git a/sysdep/unix/krt.c b/sysdep/unix/krt.c
index 73324f38..41293a06 100644
--- a/sysdep/unix/krt.c
+++ b/sysdep/unix/krt.c
@@ -131,14 +131,14 @@ prefer_addr(struct ifa *a, struct ifa *b)
 }
 
 static inline struct ifa *
-find_preferred_ifa(struct iface *i, ip_addr prefix, ip_addr mask)
+find_preferred_ifa(struct iface *i, const net_addr *n)
 {
   struct ifa *a, *b = NULL;
 
   WALK_LIST(a, i->addrs)
     {
       if (!(a->flags & IA_SECONDARY) &&
-	  ipa_equal(ipa_and(a->ip, mask), prefix) &&
+	  (!n || ipa_in_netX(a->ip, n)) &&
 	  (!b || prefer_addr(a, b)))
 	b = a;
     }
@@ -156,14 +156,14 @@ kif_choose_primary(struct iface *i)
   WALK_LIST(it, cf->primary)
     {
       if (!it->pattern || patmatch(it->pattern, i->name))
-	if (a = find_preferred_ifa(i, it->prefix, ipa_mkmask(it->pxlen)))
+	if (a = find_preferred_ifa(i, &it->addr))
 	  return a;
     }
 
   if (a = kif_get_primary_ip(i))
     return a;
 
-  return find_preferred_ifa(i, IPA_NONE, IPA_NONE);
+  return find_preferred_ifa(i, NULL);
 }
 
 
diff --git a/sysdep/unix/krt.h b/sysdep/unix/krt.h
index 4b66ea83..f05dc37e 100644
--- a/sysdep/unix/krt.h
+++ b/sysdep/unix/krt.h
@@ -97,8 +97,7 @@ extern struct protocol proto_unix_iface;
 struct kif_primary_item {
   node n;
   byte *pattern;
-  ip_addr prefix;
-  int pxlen;
+  net_addr addr;
 };
 
 struct kif_config {
diff --git a/sysdep/unix/unix.h b/sysdep/unix/unix.h
index 58ceab1e..6e788f08 100644
--- a/sysdep/unix/unix.h
+++ b/sysdep/unix/unix.h
@@ -80,14 +80,8 @@ static inline ip_addr ipa_from_sa(sockaddr *sa)
 static inline struct in_addr ipa_to_in4(ip_addr a)
 { return (struct in_addr) { htonl(ipa_to_u32(a)) }; }
 
-#ifdef IPV6
 static inline struct in6_addr ipa_to_in6(ip_addr a)
 { return (struct in6_addr) { .s6_addr32 = { htonl(_I0(a)), htonl(_I1(a)), htonl(_I2(a)), htonl(_I3(a)) } }; }
-#else
-/* Temporary dummy */
-static inline struct in6_addr ipa_to_in6(ip_addr a)
-{ return (struct in6_addr) { .s6_addr32 = { 0, 0, 0, 0 } }; }
-#endif
 
 void sockaddr_fill(sockaddr *sa, int af, ip_addr a, struct iface *ifa, uint port);
 int sockaddr_read(sockaddr *sa, int af, ip_addr *a, struct iface **ifa, uint *port);