diff --git a/includes/dhcpd.h b/includes/dhcpd.h
index 75f6ffe6..fd86ab25 100644
--- a/includes/dhcpd.h
+++ b/includes/dhcpd.h
@@ -1347,6 +1347,8 @@ struct iaaddr {
 	struct binding_scope *scope;		/* "set var = value;" */
 	time_t hard_lifetime_end_time;		/* time address expires */
 	time_t soft_lifetime_end_time;		/* time ephemeral expires */
+	u_int32_t prefer;			/* cached preferred lifetime */
+	u_int32_t valid;			/* cached valid lifetime */
 	struct ia_xx *ia;			/* IA for this lease */
 	struct ipv6_pool *ipv6_pool;		/* pool for this lease */
 /*
@@ -1365,6 +1367,7 @@ struct ia_xx {
 	u_int16_t ia_type;		/* IA_XX */
 	int num_iaaddr;			/* number of IAADDR for this IA */
 	int max_iaaddr;			/* space available for IAADDR */
+	time_t cltt;			/* client last transaction time */
 	struct iaaddr **iaaddr;		/* pointers to the various IAADDRs */
 };
 
diff --git a/server/confpars.c b/server/confpars.c
index 3a54da05..96e4c4b0 100644
--- a/server/confpars.c
+++ b/server/confpars.c
@@ -4082,6 +4082,8 @@ parse_ia_na_declaration(struct parse *cfile) {
 	u_int32_t iaid;
 	struct iaddr iaddr;
 	binding_state_t state;
+	u_int32_t prefer;
+	u_int32_t valid;
 	TIME end_time;
 	struct iaaddr *iaaddr;
 	struct ipv6_pool *pool;
@@ -4129,6 +4131,11 @@ parse_ia_na_declaration(struct parse *cfile) {
 		token = next_token(&val, NULL, cfile);
 		if (token == RBRACE) break;
 
+		if (token == CLTT) {
+			ia->cltt = parse_date (cfile);
+			continue;
+		}
+
 		if (token != IAADDR) {
 			parse_warn(cfile, "corrupt lease file; "
 					  "expecting IAADDR or right brace");
@@ -4152,6 +4159,7 @@ parse_ia_na_declaration(struct parse *cfile) {
 		}
 
 		state = FTS_LAST+1;
+		prefer = valid = 0;
 		end_time = -1;
 		for (;;) {
 			token = next_token(&val, NULL, cfile);
@@ -4202,6 +4210,32 @@ parse_ia_na_declaration(struct parse *cfile) {
 				}
 				break;
 
+				/* Lease preferred lifetime. */
+			      case PREFERRED_LIFE:
+				token = next_token(&val, NULL, cfile);
+				if (token != NUMBER) {
+					parse_warn(cfile, "%s is not a valid "
+							  "preferred time",
+						   val);
+					skip_to_semi(cfile);
+					continue;
+				}
+				prefer = atoi (val);
+				break;
+
+				/* Lease valid lifetime. */
+			      case MAX_LIFE:
+				token = next_token(&val, NULL, cfile);
+				if (token != NUMBER) {
+					parse_warn(cfile, "%s is not a valid "
+							  "max time",
+						   val);
+					skip_to_semi(cfile);
+					continue;
+				}
+				valid = atoi (val);
+				break;
+
 				/* Lease expiration time. */
 			      case ENDS:
 				end_time = parse_date(cfile);
@@ -4315,6 +4349,8 @@ parse_ia_na_declaration(struct parse *cfile) {
 		memcpy(&iaaddr->addr, iaddr.iabuf, sizeof(iaaddr->addr));
 		iaaddr->plen = 0;
 		iaaddr->state = state;
+		iaaddr->prefer = prefer;
+		iaaddr->valid = valid;
 		if (iaaddr->state == FTS_RELEASED)
 			iaaddr->hard_lifetime_end_time = end_time;
 
@@ -4379,6 +4415,8 @@ parse_ia_ta_declaration(struct parse *cfile) {
 	u_int32_t iaid;
 	struct iaddr iaddr;
 	binding_state_t state;
+	u_int32_t prefer;
+	u_int32_t valid;
 	TIME end_time;
 	struct iaaddr *iaaddr;
 	struct ipv6_pool *pool;
@@ -4426,6 +4464,11 @@ parse_ia_ta_declaration(struct parse *cfile) {
 		token = next_token(&val, NULL, cfile);
 		if (token == RBRACE) break;
 
+		if (token == CLTT) {
+			ia->cltt = parse_date (cfile);
+			continue;
+		}
+
 		if (token != IAADDR) {
 			parse_warn(cfile, "corrupt lease file; "
 					  "expecting IAADDR or right brace");
@@ -4449,6 +4492,7 @@ parse_ia_ta_declaration(struct parse *cfile) {
 		}
 
 		state = FTS_LAST+1;
+		prefer = valid = 0;
 		end_time = -1;
 		for (;;) {
 			token = next_token(&val, NULL, cfile);
@@ -4499,6 +4543,32 @@ parse_ia_ta_declaration(struct parse *cfile) {
 				}
 				break;
 
+				/* Lease preferred lifetime. */
+			      case PREFERRED_LIFE:
+				token = next_token(&val, NULL, cfile);
+				if (token != NUMBER) {
+					parse_warn(cfile, "%s is not a valid "
+							  "preferred time",
+						   val);
+					skip_to_semi(cfile);
+					continue;
+				}
+				prefer = atoi (val);
+				break;
+
+				/* Lease valid lifetime. */
+			      case MAX_LIFE:
+				token = next_token(&val, NULL, cfile);
+				if (token != NUMBER) {
+					parse_warn(cfile, "%s is not a valid "
+							  "max time",
+						   val);
+					skip_to_semi(cfile);
+					continue;
+				}
+				valid = atoi (val);
+				break;
+
 				/* Lease expiration time. */
 			      case ENDS:
 				end_time = parse_date(cfile);
@@ -4612,6 +4682,8 @@ parse_ia_ta_declaration(struct parse *cfile) {
 		memcpy(&iaaddr->addr, iaddr.iabuf, sizeof(iaaddr->addr));
 		iaaddr->plen = 0;
 		iaaddr->state = state;
+		iaaddr->prefer = prefer;
+		iaaddr->valid = valid;
 		if (iaaddr->state == FTS_RELEASED)
 			iaaddr->hard_lifetime_end_time = end_time;
 
@@ -4677,6 +4749,8 @@ parse_ia_pd_declaration(struct parse *cfile) {
 	struct iaddr iaddr;
 	u_int8_t plen;
 	binding_state_t state;
+	u_int32_t prefer;
+	u_int32_t valid;
 	TIME end_time;
 	struct iaaddr *iapref;
 	struct ipv6_pool *pool;
@@ -4724,6 +4798,11 @@ parse_ia_pd_declaration(struct parse *cfile) {
 		token = next_token(&val, NULL, cfile);
 		if (token == RBRACE) break;
 
+		if (token == CLTT) {
+			ia->cltt = parse_date (cfile);
+			continue;
+		}
+
 		if (token != IAPREFIX) {
 			parse_warn(cfile, "corrupt lease file; expecting "
 				   "IAPREFIX or right brace");
@@ -4747,6 +4826,7 @@ parse_ia_pd_declaration(struct parse *cfile) {
 		}
 
 		state = FTS_LAST+1;
+		prefer = valid = 0;
 		end_time = -1;
 		for (;;) {
 			token = next_token(&val, NULL, cfile);
@@ -4797,6 +4877,32 @@ parse_ia_pd_declaration(struct parse *cfile) {
 				}
 				break;
 
+				/* Lease preferred lifetime. */
+			      case PREFERRED_LIFE:
+				token = next_token(&val, NULL, cfile);
+				if (token != NUMBER) {
+					parse_warn(cfile, "%s is not a valid "
+							  "preferred time",
+						   val);
+					skip_to_semi(cfile);
+					continue;
+				}
+				prefer = atoi (val);
+				break;
+
+				/* Lease valid lifetime. */
+			      case MAX_LIFE:
+				token = next_token(&val, NULL, cfile);
+				if (token != NUMBER) {
+					parse_warn(cfile, "%s is not a valid "
+							  "max time",
+						   val);
+					skip_to_semi(cfile);
+					continue;
+				}
+				valid = atoi (val);
+				break;
+
 				/* Prefix expiration time. */
 			      case ENDS:
 				end_time = parse_date(cfile);
@@ -4910,6 +5016,8 @@ parse_ia_pd_declaration(struct parse *cfile) {
 		memcpy(&iapref->addr, iaddr.iabuf, sizeof(iapref->addr));
 		iapref->plen = plen;
 		iapref->state = state;
+		iapref->prefer = prefer;
+		iapref->valid = valid;
 		if (iapref->state == FTS_RELEASED)
 			iapref->hard_lifetime_end_time = end_time;
 
diff --git a/server/db.c b/server/db.c
index 29b140d3..42120d31 100644
--- a/server/db.c
+++ b/server/db.c
@@ -548,6 +548,15 @@ write_ia(const struct ia_xx *ia) {
 	if (fprintf_ret < 0) {
 		goto error_exit;
 	}
+	if (ia->cltt != MIN_TIME) {
+		tval = print_time(ia->cltt);
+		if (tval == NULL) {
+			goto error_exit;
+		}
+		if (fprintf(db_file, "  cltt %s\n", tval) < 0) {
+			goto error_exit;
+		}
+	}
 	for (i=0; i<ia->num_iaaddr; i++) {
 		iaaddr = ia->iaaddr[i];
 
@@ -570,6 +579,14 @@ write_ia(const struct ia_xx *ia) {
 			    binding_state) < 0) {
 			goto error_exit;
 		}
+		if (fprintf(db_file, "    preferred-life %u\n",
+			    (unsigned)iaaddr->prefer) < 0) {
+			goto error_exit;
+		}
+		if (fprintf(db_file, "    max-life %u\n",
+			    (unsigned)iaaddr->valid) < 0) {
+			goto error_exit;
+		}
 
 		/* Note that from here on out, the \n is prepended to the
 		 * next write, rather than appended to the current write.
diff --git a/server/dhcpleasequery.c b/server/dhcpleasequery.c
index 0c4174a6..97fc4e0e 100644
--- a/server/dhcpleasequery.c
+++ b/server/dhcpleasequery.c
@@ -656,10 +656,6 @@ dhcpleasequery(struct packet *packet, int ms_nulltp) {
  *
  * TODO: RFC5007 ORO in query-options.
  *
- * TODO: RFC5007 not default preferred and valid time.
- *
- * TODO: RFC5007 not zero Client Last Transaction Time (clt-time).
- *
  * TODO: RFC5007 lq-relay-data.
  *
  * TODO: RFC5007 lq-client-link.
@@ -952,10 +948,9 @@ process_lq_by_address(struct lq6_state *lq) {
 	}
 	data.data = data.buffer->data;
 	memcpy(data.buffer->data, &iaaddr->addr, 16);
-	lifetime = DEFAULT_DEFAULT_LEASE_TIME;
-	lifetime = (lifetime / 2) + (lifetime / 8);
+	lifetime = iaaddr->prefer;
 	putULong(data.buffer->data + 16, lifetime);
-	lifetime = DEFAULT_DEFAULT_LEASE_TIME;
+	lifetime = iaaddr->valid;
 	putULong(data.buffer->data + 20, lifetime);
 	if (!save_option_buffer(&dhcpv6_universe, opt_state,
 				NULL, (unsigned char *)data.data, data.len,
@@ -965,7 +960,7 @@ process_lq_by_address(struct lq6_state *lq) {
 	}
 	data_string_forget(&data, MDL);
 
-	lifetime = 0;
+	lifetime = htonl(iaaddr->ia->cltt);
 	if (!save_option_buffer(&dhcpv6_universe, opt_state,
 				NULL, (unsigned char *)&lifetime, 4,
 				D6O_CLT_TIME, 0)) {
diff --git a/server/dhcpv6.c b/server/dhcpv6.c
index 2dad33ed..6fde7584 100644
--- a/server/dhcpv6.c
+++ b/server/dhcpv6.c
@@ -1827,6 +1827,7 @@ reply_process_ia_na(struct reply_state *reply, struct option_cache *ia) {
 		}
 
 		/* Put new ia into the hash. */
+		reply->ia->cltt = cur_time;
 		ia_id = &reply->ia->iaid_duid;
 		ia_hash_add(ia_na_active, (unsigned char *)ia_id->data,
 			    ia_id->len, reply->ia, MDL);
@@ -2441,6 +2442,7 @@ reply_process_ia_ta(struct reply_state *reply, struct option_cache *ia) {
 		}
 
 		/* Put new ia into the hash. */
+		reply->ia->cltt = cur_time;
 		ia_id = &reply->ia->iaid_duid;
 		ia_hash_add(ia_ta_active, (unsigned char *)ia_id->data,
 			    ia_id->len, reply->ia, MDL);
@@ -2750,6 +2752,10 @@ reply_process_is_addressed(struct reply_state *reply,
 
 	/* Perform dynamic lease related update work. */
 	if (reply->lease != NULL) {
+		/* Cached lifetimes */
+		reply->lease->prefer = reply->send_prefer;
+		reply->lease->valid = reply->send_valid;
+
 		/* Advance (or rewind) the valid lifetime. */
 		if (reply->buf.reply.msg_type == DHCPV6_REPLY) {
 			reply->lease->soft_lifetime_end_time =
@@ -3186,6 +3192,7 @@ reply_process_ia_pd(struct reply_state *reply, struct option_cache *ia) {
 		}
 
 		/* Put new ia into the hash. */
+		reply->ia->cltt = cur_time;
 		ia_id = &reply->ia->iaid_duid;
 		ia_hash_add(ia_pd_active, (unsigned char *)ia_id->data,
 			    ia_id->len, reply->ia, MDL);
@@ -3698,6 +3705,10 @@ reply_process_is_prefixed(struct reply_state *reply,
 
 	/* Perform dynamic prefix related update work. */
 	if (reply->lease != NULL) {
+		/* Cached lifetimes */
+		reply->lease->prefer = reply->send_prefer;
+		reply->lease->valid = reply->send_valid;
+
 		/* Advance (or rewind) the valid lifetime. */
 		if (reply->buf.reply.msg_type == DHCPV6_REPLY) {
 			reply->lease->soft_lifetime_end_time =
@@ -4276,6 +4287,7 @@ ia_na_match_decline(const struct data_string *client_id,
 		  	    tmp_addr, sizeof(tmp_addr)));
 	if (lease != NULL) {
 		decline_lease6(lease->ipv6_pool, lease);
+		lease->ia->cltt = cur_time;
 		write_ia(lease->ia);
 	}
 }
@@ -4692,6 +4704,7 @@ ia_na_match_release(const struct data_string *client_id,
 		 inet_ntop(AF_INET6, iaaddr->data, tmp_addr, sizeof(tmp_addr)));
 	if (lease != NULL) {
 		release_lease6(lease->ipv6_pool, lease);
+		lease->ia->cltt = cur_time;
 		write_ia(lease->ia);
 	}
 }
@@ -4784,6 +4797,7 @@ ia_pd_match_release(const struct data_string *client_id,
 		 (unsigned) getUChar(iapref->data + 8));
 	if (prefix != NULL) {
 		release_lease6(prefix->ipv6_pool, prefix);
+		prefix->ia->cltt = cur_time;
 		write_ia(prefix->ia);
 	}
 }