diff --git a/src/dhcpd-pools.c b/src/dhcpd-pools.c
index 692c4ff..c50fcfb 100644
--- a/src/dhcpd-pools.c
+++ b/src/dhcpd-pools.c
@@ -248,7 +248,7 @@ int main(int argc, char **argv)
 
 	/* Do the job */
 	prepare_memory();
-	xstrstr = xstrstr_init;
+	set_ipv_functions(VERSION_UNKNOWN);
 	parse_config(true, config.dhcpdconf_file, shared_networks);
 
 	parse_leases();
diff --git a/src/dhcpd-pools.h b/src/dhcpd-pools.h
index 5068380..29d5e4c 100644
--- a/src/dhcpd-pools.h
+++ b/src/dhcpd-pools.h
@@ -189,6 +189,7 @@ unsigned int RANGES;
 
 /* Function prototypes */
 int prepare_memory(void);
+void set_ipv_functions(int version);
 int parse_leases(void);
 void parse_config(int, const char *__restrict,
 		  struct shared_network_t *__restrict)
@@ -199,11 +200,26 @@ void flip_ranges(struct range_t *__restrict ranges,
 		 struct range_t *__restrict tmp_ranges)
     __attribute__ ((nonnull(1, 2)));
 /* support functions */
-int parse_ipaddr(const char *restrict src, union ipaddr_t *restrict dst);
-void copy_ipaddr(union ipaddr_t *restrict dst,
-		 const union ipaddr_t *restrict src);
-const char *ntop_ipaddr(const union ipaddr_t *ip);
-double get_range_size(const struct range_t *r);
+int (*parse_ipaddr)(const char *restrict src, union ipaddr_t *restrict dst);
+int parse_ipaddr_init(const char *restrict src, union ipaddr_t *restrict dst);
+int parse_ipaddr_v4(const char *restrict src, union ipaddr_t *restrict dst);
+int parse_ipaddr_v6(const char *restrict src, union ipaddr_t *restrict dst);
+
+void (*copy_ipaddr)(union ipaddr_t *restrict dst, const union ipaddr_t *restrict src);
+void copy_ipaddr_init(union ipaddr_t *restrict dst, const union ipaddr_t *restrict src);
+void copy_ipaddr_v4(union ipaddr_t *restrict dst, const union ipaddr_t *restrict src);
+void copy_ipaddr_v6(union ipaddr_t *restrict dst, const union ipaddr_t *restrict src);
+
+const char *(*ntop_ipaddr)(const union ipaddr_t *ip);
+const char *ntop_ipaddr_init(const union ipaddr_t *ip);
+const char *ntop_ipaddr_v4(const union ipaddr_t *ip);
+const char *ntop_ipaddr_v6(const union ipaddr_t *ip);
+
+double (*get_range_size)(const struct range_t *r);
+double get_range_size_init(const struct range_t *r);
+double get_range_size_v4(const struct range_t *r);
+double get_range_size_v6(const struct range_t *r);
+
 int (*xstrstr)(const char *__restrict str);
 int xstrstr_init(const char *__restrict str)
 # if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
@@ -227,7 +243,11 @@ void print_version(void) __attribute__ ((noreturn));
 void usage(int status) __attribute__ ((noreturn));
 /* qsort required functions... */
 /* ...for ranges and... */
-int ipcomp(const union ipaddr_t *restrict a, const union ipaddr_t *restrict b);
+int (*ipcomp)(const union ipaddr_t *restrict a, const union ipaddr_t *restrict b);
+int ipcomp_init(const union ipaddr_t *restrict a, const union ipaddr_t *restrict b);
+int ipcomp_v4(const union ipaddr_t *restrict a, const union ipaddr_t *restrict b);
+int ipcomp_v6(const union ipaddr_t *restrict a, const union ipaddr_t *restrict b);
+
 int comp_cur(struct range_t *r1, struct range_t *r2);
 int comp_double(double f1, double f2);
 int comp_ip(struct range_t *r1, struct range_t *r2);
@@ -258,8 +278,16 @@ int output_alarming(void);
 /* Memory release, file closing etc */
 void clean_up(void);
 /* Hash functions */
-void add_lease(union ipaddr_t *ip, enum ltype type);
-struct leases_t *find_lease(union ipaddr_t *ip);
+void (*add_lease)(union ipaddr_t *ip, enum ltype type);
+void add_lease_init(union ipaddr_t *ip, enum ltype type);
+void add_lease_v4(union ipaddr_t *ip, enum ltype type);
+void add_lease_v6(union ipaddr_t *ip, enum ltype type);
+
+struct leases_t *(*find_lease)(union ipaddr_t *ip);
+struct leases_t *find_lease_init(union ipaddr_t *ip);
+struct leases_t *find_lease_v4(union ipaddr_t *ip);
+struct leases_t *find_lease_v6(union ipaddr_t *ip);
+
 void delete_lease(struct leases_t *lease);
 void delete_all_leases(void);
 
diff --git a/src/hash.c b/src/hash.c
index d9a1d77..d598b74 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -47,17 +47,27 @@
 /*! \brief Add a lease to hash array.
  * \param addr Binary IP to be added in leases hash.
  * \param type Lease state of the IP. */
-void add_lease(union ipaddr_t *addr, enum ltype type)
+void add_lease_init(union ipaddr_t *addr __attribute__((unused)), enum ltype type __attribute__((unused)))
+{
+}
+
+void add_lease_v4(union ipaddr_t *addr, enum ltype type)
 {
 	struct leases_t *l;
 	l = xmalloc(sizeof(struct leases_t));
 	copy_ipaddr(&l->ip, addr);
 	l->type = type;
-	if (config.dhcp_version == VERSION_6) {
-		HASH_ADD_V6(leases, ip.v6, l);
-	} else {
-		HASH_ADD_INT(leases, ip.v4, l);
-	}
+	HASH_ADD_INT(leases, ip.v4, l);
+	l->ethernet = NULL;
+}
+
+void add_lease_v6(union ipaddr_t *addr, enum ltype type)
+{
+	struct leases_t *l;
+	l = xmalloc(sizeof(struct leases_t));
+	copy_ipaddr(&l->ip, addr);
+	l->type = type;
+	HASH_ADD_V6(leases, ip.v6, l);
 	l->ethernet = NULL;
 }
 
@@ -65,15 +75,22 @@ void add_lease(union ipaddr_t *addr, enum ltype type)
  * \param addr Binary IP searched from leases hash.
  * \return A lease structure about requested IP, or NULL.
  */
-struct leases_t *find_lease(union ipaddr_t *addr)
+struct leases_t *find_lease_init(union ipaddr_t *addr __attribute__((unused)))
+{
+	return NULL;
+}
+
+struct leases_t *find_lease_v4(union ipaddr_t *addr)
 {
 	struct leases_t *l;
+	HASH_FIND_INT(leases, &addr->v4, l);
+	return l;
+}
 
-	if (config.dhcp_version == VERSION_6) {
-		HASH_FIND_V6(leases, &addr->v6, l);
-	} else {
-		HASH_FIND_INT(leases, &addr->v4, l);
-	}
+struct leases_t *find_lease_v6(union ipaddr_t *addr)
+{
+	struct leases_t *l;
+	HASH_FIND_V6(leases, &addr->v4, l);
 	return l;
 }
 
diff --git a/src/other.c b/src/other.c
index 4e56e86..75158a0 100644
--- a/src/other.c
+++ b/src/other.c
@@ -55,36 +55,90 @@
 #include <unistd.h>
 #include <limits.h>
 
+/*! \brief Set function pointers depending on IP version.
+ * \param ip IP version.
+ */
+void set_ipv_functions(int version)
+{
+	switch (version) {
+
+	case VERSION_4:
+		config.dhcp_version = version;
+		add_lease = add_lease_v4;
+		copy_ipaddr = copy_ipaddr_v4;
+		find_lease = find_lease_v4;
+		get_range_size = get_range_size_v4;
+		ipcomp = ipcomp_v4;
+		ntop_ipaddr = ntop_ipaddr_v4;
+		parse_ipaddr = parse_ipaddr_v4;
+		xstrstr = xstrstr_v4;
+		break;
+
+	case VERSION_6:
+		config.dhcp_version = version;
+		add_lease = add_lease_v6;
+		copy_ipaddr = copy_ipaddr_v6;
+		find_lease = find_lease_v6;
+		get_range_size = get_range_size_v6;
+		ipcomp = ipcomp_v6;
+		ntop_ipaddr = ntop_ipaddr_v6;
+		parse_ipaddr = parse_ipaddr_v6;
+		xstrstr = xstrstr_v6;
+		break;
+
+	case VERSION_UNKNOWN:
+		config.dhcp_version = version;
+		add_lease = add_lease_init;
+		copy_ipaddr = copy_ipaddr_init;
+		find_lease = find_lease_init;
+		get_range_size = get_range_size_init;
+		ipcomp = ipcomp_init;
+		ntop_ipaddr = ntop_ipaddr_init;
+		parse_ipaddr = parse_ipaddr_init;
+		xstrstr = xstrstr_init;
+		break;
+
+	default:
+		abort();
+
+	}
+	return;
+}
+
 /*! \brief Convert text string IP address from either IPv4 or IPv6 to an integer.
  * \param src An IP string in either format.
  * \param dst An union which will hold conversion result.
  * \return Was parsing successful.
  */
-int parse_ipaddr(const char *restrict src, union ipaddr_t *restrict dst)
+int parse_ipaddr_init(const char *restrict src, union ipaddr_t *restrict dst)
+{
+	struct in_addr addr;
+	struct in6_addr addr6;
+	if (inet_aton(src, &addr) == 1) {
+		set_ipv_functions(VERSION_4);
+	} else if (inet_pton(AF_INET6, src, &addr6) == 1) {
+		set_ipv_functions(VERSION_6);
+	} else {
+		return 0;
+	}
+	return parse_ipaddr(src, dst);
+}
+
+int parse_ipaddr_v4(const char *restrict src, union ipaddr_t *restrict dst)
 {
 	int rv;
-	if (config.dhcp_version == VERSION_UNKNOWN) {
-		struct in_addr addr;
-		struct in6_addr addr6;
-		if (inet_aton(src, &addr) == 1) {
-			config.dhcp_version = VERSION_4;
-			xstrstr = xstrstr_v4;
-		} else if (inet_pton(AF_INET6, src, &addr6) == 1) {
-			config.dhcp_version = VERSION_6;
-			xstrstr = xstrstr_v6;
-		} else {
-			return 0;
-		}
-	}
-	if (config.dhcp_version == VERSION_6) {
-		struct in6_addr addr;
-		rv = inet_pton(AF_INET6, src, &addr);
-		memcpy(&dst->v6, addr.s6_addr, sizeof(addr.s6_addr));
-	} else {
-		struct in_addr addr;
-		rv = inet_aton(src, &addr);
-		dst->v4 = ntohl(addr.s_addr);
-	}
+	struct in_addr addr;
+	rv = inet_aton(src, &addr);
+	dst->v4 = ntohl(addr.s_addr);
+	return rv == 1;
+}
+
+int parse_ipaddr_v6(const char *restrict src, union ipaddr_t *restrict dst)
+{
+	int rv;
+	struct in6_addr addr;
+	rv = inet_pton(AF_INET6, src, &addr);
+	memcpy(&dst->v6, addr.s6_addr, sizeof(addr.s6_addr));
 	return rv == 1;
 }
 
@@ -92,14 +146,21 @@ int parse_ipaddr(const char *restrict src, union ipaddr_t *restrict dst)
  *
  * \param dst Destination for a binary IP address.
  * \param src Sourse of an IP address. */
-void copy_ipaddr(union ipaddr_t *restrict dst,
+void copy_ipaddr_init(union ipaddr_t *restrict dst __attribute__((unused)),
+		      const union ipaddr_t *restrict src __attribute__((unused)))
+{
+}
+
+void copy_ipaddr_v4(union ipaddr_t *restrict dst,
+		    const union ipaddr_t *restrict src)
+{
+	dst->v4 = src->v4;
+}
+
+void copy_ipaddr_v6(union ipaddr_t *restrict dst,
 		 const union ipaddr_t *restrict src)
 {
-	if (config.dhcp_version == VERSION_6) {
-		memcpy(&dst->v6, &src->v6, sizeof(src->v6));
-	} else {
-		dst->v4 = src->v4;
-	}
+	memcpy(&dst->v6, &src->v6, sizeof(src->v6));
 }
 
 /*! \brief Convert an address to string. This function will convert the
@@ -110,19 +171,27 @@ void copy_ipaddr(union ipaddr_t *restrict dst,
  * \param ip Binary IP address.
  * \return Printable address.
  */
-const char *ntop_ipaddr(const union ipaddr_t *ip)
+const char *ntop_ipaddr_init(const union ipaddr_t *ip __attribute__((unused)))
+{
+	static char buffer = '\0';
+	return &buffer;
+}
+
+const char *ntop_ipaddr_v4(const union ipaddr_t *ip)
+{
+	static char buffer[sizeof("255.255.255.255")];
+	struct in_addr addr;
+	addr.s_addr = htonl(ip->v4);
+	return inet_ntop(AF_INET, &addr, buffer, sizeof(buffer));
+}
+
+const char *ntop_ipaddr_v6(const union ipaddr_t *ip)
 {
 	static char
 	    buffer[sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255")];
-	if (config.dhcp_version == VERSION_6) {
-		struct in6_addr addr;
-		memcpy(addr.s6_addr, ip->v6, sizeof(addr.s6_addr));
-		return inet_ntop(AF_INET6, &addr, buffer, sizeof(buffer));
-	} else {
-		struct in_addr addr;
-		addr.s_addr = htonl(ip->v4);
-		return inet_ntop(AF_INET, &addr, buffer, sizeof(buffer));
-	}
+	struct in6_addr addr;
+	memcpy(addr.s6_addr, ip->v6, sizeof(addr.s6_addr));
+	return inet_ntop(AF_INET6, &addr, buffer, sizeof(buffer));
 }
 
 /*! \brief Calculate how many addresses there are in a range.
@@ -131,23 +200,28 @@ const char *ntop_ipaddr(const union ipaddr_t *ip)
  * and last IP in the range.
  * \return Size of a range.
  */
-double get_range_size(const struct range_t *r)
+double get_range_size_init(const struct range_t *r __attribute__((unused)))
 {
-	if (config.dhcp_version == VERSION_6) {
-		double size = 0;
-		int i;
-		/* When calculating the size of an IPv6 range overflow may
-		 * occur.  In that case only the last LONG_BIT bits are
-		 * preserved, thus we just skip the first (16 - LONG_BIT)
-		 * bits...  */
-		for (i = 0; i < 16; i++) {
-			size *= 256;
-			size += (int)r->last_ip.v6[i] - (int)r->first_ip.v6[i];
-		}
-		return size + 1;
-	} else {
-		return r->last_ip.v4 - r->first_ip.v4 + 1;
+	return 0;
+}
+
+double get_range_size_v4(const struct range_t *r)
+{
+	return r->last_ip.v4 - r->first_ip.v4 + 1;
+}
+
+double get_range_size_v6(const struct range_t *r)
+{
+	double size = 0;
+	int i;
+	/* When calculating the size of an IPv6 range overflow may occur.
+	 * In that case only the last LONG_BIT bits are preserved, thus
+	 * we just skip the first (16 - LONG_BIT) bits...  */
+	for (i = 0; i < 16; i++) {
+		size *= 256;
+		size += (int)r->last_ip.v6[i] - (int)r->first_ip.v6[i];
 	}
+	return size + 1;
 }
 
 /*! \fn xstrstr_init(const char *restrict str)
@@ -164,12 +238,10 @@ int
     xstrstr_init(const char *restrict str)
 {
 	if (memcmp("lease ", str, 6)) {
-		config.dhcp_version = VERSION_4;
-		xstrstr = xstrstr_v4;
+		set_ipv_functions(VERSION_4);
 		return PREFIX_LEASE;
 	} else if (memcmp("  iaaddr ", str, 9)) {
-		config.dhcp_version = VERSION_6;
-		xstrstr = xstrstr_v6;
+		set_ipv_functions(VERSION_6);
 		return PREFIX_LEASE;
 	}
 	return NUM_OF_PREFIX;
diff --git a/src/sort.c b/src/sort.c
index badb2ab..a2eaa18 100644
--- a/src/sort.c
+++ b/src/sort.c
@@ -54,17 +54,26 @@
  * \param b Binary IP address.
  * \return If a < b return -1, if a < b return 1, when they are equal return 0.
  */
-int ipcomp(const union ipaddr_t *restrict a, const union ipaddr_t *restrict b)
+int ipcomp_init(const union ipaddr_t *restrict a __attribute__((unused)),
+		const union ipaddr_t *restrict b __attribute__((unused)))
 {
-	if (config.dhcp_version == VERSION_6) {
-		return memcmp(&a->v6, &b->v6, sizeof(a->v6));
-	} else {
-		if (a->v4 < b->v4)
-			return -1;
-		if (a->v4 > b->v4)
-			return 1;
-		return 0;
-	}
+	return 0;
+}
+
+int ipcomp_v4(const union ipaddr_t *restrict a,
+	      const union ipaddr_t *restrict b)
+{
+	if (a->v4 < b->v4)
+		return -1;
+	if (a->v4 > b->v4)
+		return 1;
+	return 0;
+}
+
+int ipcomp_v6(const union ipaddr_t *restrict a,
+	      const union ipaddr_t *restrict b)
+{
+	return memcmp(&a->v6, &b->v6, sizeof(a->v6));
 }
 
 /*! \brief Compare IP address in leases. Suitable for sorting range table.