diff --git a/accel-pppd/ctrl/ipoe/ipoe.c b/accel-pppd/ctrl/ipoe/ipoe.c
index b8082a6..e11dada 100644
--- a/accel-pppd/ctrl/ipoe/ipoe.c
+++ b/accel-pppd/ctrl/ipoe/ipoe.c
@@ -116,6 +116,7 @@ static int conf_ifcfg = 1;
 static int conf_nat;
 static int conf_arp;
 static int conf_ipv6;
+static int conf_nak_for_unknown;
 static uint32_t conf_src;
 static const char *conf_ip_pool;
 static const char *conf_l4_redirect_pool;
@@ -1807,6 +1808,11 @@ static void __ipoe_recv_dhcpv4(struct dhcpv4_serv *dhcpv4, struct dhcpv4_packet
 				log_debug("%s: recv ", serv->ifname);
 				dhcpv4_print_packet(pack, 0, log_debug);
 			}
+			 if(conf_nak_for_unknown){
+                               log_debug("%s: unknown session request detected\n", serv->ifname);
+                               dhcpv4_send_nak(dhcpv4, pack);
+                               goto out;
+                       }
 
 			if (pack->src_addr) {
 				dhcpv4_send_nak(dhcpv4, pack);
@@ -3925,6 +3931,12 @@ static void load_config(void)
 	else
 		conf_weight = 0;
 
+	opt = conf_get_opt("ipoe", "nak-for-unknown");
+	if (opt)
+                conf_nak_for_unknown = atoi(opt);
+        else
+                conf_nak_for_unknown = 0;
+
 #ifdef RADIUS
 	if (triton_module_loaded("radius"))
 		load_radius_attrs();