diff --git a/includes/dhcp.h b/includes/dhcp.h
index f916468..60f4d96 100644
--- a/includes/dhcp.h
+++ b/includes/dhcp.h
@@ -184,6 +184,7 @@ struct dhcp_packet {
 #define RAI_REMOTE_ID	2
 #define RAI_AGENT_ID	3
 #define RAI_LINK_SELECT	5
+#define RAI_RELAY_PORT  19
 
 /* FQDN suboptions: */
 #define FQDN_NO_CLIENT_UPDATE		1
diff --git a/includes/dhcpd.h b/includes/dhcpd.h
index 261714d..2bf09f6 100644
--- a/includes/dhcpd.h
+++ b/includes/dhcpd.h
@@ -472,6 +472,9 @@ struct packet {
 	/* Propogates server value SV_ECHO_CLIENT_ID so it is available
          * in cons_options() */
 	int sv_echo_client_id;
+
+	/* Relay port check */
+	isc_boolean_t relay_source_port;
 };
 
 /*
@@ -2397,6 +2400,8 @@ void eval_network_statements(struct option_state **options,
 			    struct packet *packet,
 			    struct group *network_group);
 
+uint16_t dhcp_check_relayport(struct packet *packet);
+
 /* dhcpleasequery.c */
 void dhcpleasequery (struct packet *, int);
 void dhcpv6_leasequery (struct data_string *, struct packet *);
diff --git a/server/dhcp.c b/server/dhcp.c
index c9b3632..1d152d5 100644
--- a/server/dhcp.c
+++ b/server/dhcp.c
@@ -1061,6 +1061,17 @@ void dhcpdecline (packet, ms_nulltp)
 		lease_dereference (&lease, MDL);
 }
 
+uint16_t dhcp_check_relayport (packet)
+struct packet *packet;
+{
+	if (lookup_option(&agent_universe, packet->options,
+			  RAI_RELAY_PORT) != NULL) {
+		return (packet->client_port);
+	}
+
+	return (0);
+}
+
 void dhcpinform (packet, ms_nulltp)
 	struct packet *packet;
 	int ms_nulltp;
@@ -1081,6 +1092,7 @@ void dhcpinform (packet, ms_nulltp)
 	isc_boolean_t zeroed_ciaddr;
 	struct interface_info *interface;
 	int result, h_m_client_ip = 0;
+	uint16_t relay_port;
 	struct host_decl  *host = NULL, *hp = NULL, *h;
 #if defined (DEBUG_INFORM_HOST)
 	int h_w_fixed_addr = 0;
@@ -1155,6 +1167,8 @@ void dhcpinform (packet, ms_nulltp)
 		oc = lookup_option(&dhcp_universe, packet->options,
 				   DHO_SUBNET_SELECTION);
 
+	relay_port = dhcp_check_relayport(packet);
+
 	memset(&d1, 0, sizeof d1);
 	if (oc && evaluate_option_cache(&d1, packet, NULL, NULL,
 					packet->options, NULL,
@@ -1672,7 +1686,7 @@ void dhcpinform (packet, ms_nulltp)
 	 */
 	if (!raw.ciaddr.s_addr && gip.len) {
 		memcpy(&to.sin_addr, gip.iabuf, 4);
-		to.sin_port = local_port;
+		to.sin_port = (relay_port) ? relay_port : local_port;
 		raw.flags |= htons(BOOTP_BROADCAST);
 	} else {
 		gip.len = 0;
@@ -1729,6 +1743,7 @@ void nak_lease (packet, cip, network_group)
 	unsigned char nak = DHCPNAK;
 	struct packet outgoing;
 	unsigned i;
+	uint16_t relay_port;
 	struct option_state *options = (struct option_state *)0;
 	struct option_cache *oc = (struct option_cache *)0;
 	struct option_state *eval_options = NULL;
@@ -1777,6 +1792,8 @@ void nak_lease (packet, cip, network_group)
 	save_option (&dhcp_universe, options, oc);
 	option_cache_dereference (&oc, MDL);
 
+	relay_port = dhcp_check_relayport(packet);
+
 	/* Setup the options at the global and subnet scopes.  These
 	 * may be used to locate sever id option if enabled as well
 	 * for echo-client-id further on. (This allocates eval_options). */
@@ -1905,7 +1922,7 @@ void nak_lease (packet, cip, network_group)
 	if (raw.giaddr.s_addr) {
 		to.sin_addr = raw.giaddr;
 		if (raw.giaddr.s_addr != htonl (INADDR_LOOPBACK))
-			to.sin_port = local_port;
+			to.sin_port = (relay_port) ? relay_port : local_port;
 		else
 			to.sin_port = remote_port; /* for testing. */
 
@@ -3717,6 +3734,7 @@ void dhcp_reply (lease)
 	int result;
 	struct lease_state *state = lease -> state;
 	int nulltp, bootpp, unicastp = 1;
+	uint16_t relay_port;
 	struct data_string d1;
 	const char *s;
 
@@ -3886,11 +3904,13 @@ void dhcp_reply (lease)
 #endif
 	memset (to.sin_zero, 0, sizeof to.sin_zero);
 
+	relay_port = dhcp_check_relayport(state->packet);
+
 	/* If this was gatewayed, send it back to the gateway... */
 	if (raw.giaddr.s_addr) {
 		to.sin_addr = raw.giaddr;
 		if (raw.giaddr.s_addr != htonl (INADDR_LOOPBACK))
-			to.sin_port = local_port;
+			to.sin_port = (relay_port) ? relay_port : local_port;
 		else
 			to.sin_port = remote_port; /* For debugging. */
 
diff --git a/server/dhcpleasequery.c b/server/dhcpleasequery.c
index 75a0e72..9bd4d7e 100644
--- a/server/dhcpleasequery.c
+++ b/server/dhcpleasequery.c
@@ -152,6 +152,7 @@ dhcpleasequery(struct packet *packet, int ms_nulltp) {
 	u_int32_t time_rebinding;
 	u_int32_t time_expiry;
 	u_int32_t client_last_transaction_time;
+	uint16_t relay_port;
 	struct sockaddr_in to;
 	struct in_addr siaddr;
 	struct data_string prl;
@@ -660,12 +661,14 @@ dhcpleasequery(struct packet *packet, int ms_nulltp) {
 #endif
 	memset(to.sin_zero, 0, sizeof(to.sin_zero));
 
+	relay_port = dhcp_check_relayport(packet);
+
 	/* 
 	 * Leasequery packets are be sent to the gateway address.
 	 */
 	to.sin_addr = packet->raw->giaddr;
 	if (packet->raw->giaddr.s_addr != htonl(INADDR_LOOPBACK)) {
-		to.sin_port = local_port;
+		to.sin_port = (relay_port) ? relay_port : local_port;
 	} else {
 		to.sin_port = remote_port; /* XXXSK: For debugging. */
 	}
diff --git a/server/stables.c b/server/stables.c
index 445ef0f..05ce76e 100644
--- a/server/stables.c
+++ b/server/stables.c
@@ -169,6 +169,7 @@ static struct option agent_options[] = {
 	{ "agent-id", "I",			&agent_universe,   3, 1 },
 	{ "DOCSIS-device-class", "L",		&agent_universe,   4, 1 },
 	{ "link-selection", "I",		&agent_universe,   5, 1 },
+	{ "relay-port", "Z",		        &agent_universe,  19, 1 },
 	{ NULL, NULL, NULL, 0, 0 }
 };