diff --git a/src/core/ipv4/ip.c b/src/core/ipv4/ip.c
index b7ed02e3..e39334a5 100644
--- a/src/core/ipv4/ip.c
+++ b/src/core/ipv4/ip.c
@@ -73,57 +73,6 @@ ip_init(void)
 {
 }
 
-/* ip_lookup:
- *
- * An experimental feature that will be changed in future versions. Do
- * not depend on it yet...
- */
-
-#ifdef LWIP_DEBUG
-u8_t
-ip_lookup(void *header, struct netif *inp)
-{
-  struct ip_hdr *iphdr;
-
-  iphdr = header;
-
-  /* not IP v4? */
-  if (IPH_V(iphdr) != 4) {
-    return 0;
-  }
-
-  /* Immediately accept/decline packets that are fragments or has
-     options. */
-#if IP_REASSEMBLY == 0
-  /*  if ((IPH_OFFSET(iphdr) & htons(IP_OFFMASK | IP_MF)) != 0) {
-    return 0;
-    }*/
-#endif /* IP_REASSEMBLY == 0 */
-
-#if IP_OPTIONS == 0
-  if (IPH_HL(iphdr) != 5) {
-    return 0;
-  }
-#endif /* IP_OPTIONS == 0 */
-
-  switch (IPH_PROTO(iphdr)) {
-#if LWIP_UDP
-  case IP_PROTO_UDP:
-  case IP_PROTO_UDPLITE:
-    return udp_lookup(iphdr, inp);
-#endif /* LWIP_UDP */
-#if LWIP_TCP
-  case IP_PROTO_TCP:
-    return 1;
-#endif /* LWIP_TCP */
-  case IP_PROTO_ICMP:
-    return 1;
-  default:
-    return 0;
-  }
-}
-#endif /* LWIP_DEBUG */
-
 /* ip_route:
  *
  * Finds the appropriate network interface for a given IP address. It
diff --git a/src/core/udp.c b/src/core/udp.c
index 80c1b0fd..a95cb770 100644
--- a/src/core/udp.c
+++ b/src/core/udp.c
@@ -71,76 +71,6 @@ udp_init(void)
   udp_pcbs = pcb_cache = NULL;
 }
 
-
-/* udp_lookup:
- *
- * An experimental feature that will be changed in future versions. Do
- * not depend on it yet...
- */
-
-#ifdef LWIP_DEBUG
-u8_t
-udp_lookup(struct ip_hdr *iphdr, struct netif *inp)
-{
-  struct udp_pcb *pcb;
-  struct udp_hdr *udphdr;
-  u16_t src, dest;
-
-    PERF_START;
-  (void)inp;
-
-    udphdr = (struct udp_hdr *)(u8_t *)iphdr + IPH_HL(iphdr) * 4;
-
-  src = ntohs(udphdr->src);
-  dest = ntohs(udphdr->dest);
-
-    pcb = pcb_cache;
-  if (pcb != NULL &&
-    pcb->remote_port == src &&
-    pcb->local_port == dest &&
-    (ip_addr_isany(&pcb->remote_ip) ||
-    ip_addr_cmp(&(pcb->remote_ip), &(iphdr->src))) &&
-    (ip_addr_isany(&pcb->local_ip) ||
-    ip_addr_cmp(&(pcb->local_ip), &(iphdr->dest)))) {
-    return 1;
-  }
-  else {
-    for(pcb = udp_pcbs; pcb != NULL; pcb = pcb->next) {
-      if (pcb->remote_port == src &&
-   pcb->local_port == dest &&
-   (ip_addr_isany(&pcb->remote_ip) ||
-    ip_addr_cmp(&(pcb->remote_ip), &(iphdr->src))) &&
-   (ip_addr_isany(&pcb->local_ip) ||
-    ip_addr_cmp(&(pcb->local_ip), &(iphdr->dest)))) {
-  pcb_cache = pcb;
-        break;
-        }
-    }
-
-    if (pcb == NULL) {
-      for(pcb = udp_pcbs; pcb != NULL; pcb = pcb->next) {
-  if (pcb->remote_port == 0 &&
-     pcb->local_port == dest &&
-     (ip_addr_isany(&pcb->remote_ip) ||
-      ip_addr_cmp(&(pcb->remote_ip), &(iphdr->src))) &&
-     (ip_addr_isany(&pcb->local_ip) ||
-      ip_addr_cmp(&(pcb->local_ip), &(iphdr->dest)))) {
-        break;
-        }
-      }
-    }
-  }
-
-  PERF_STOP("udp_lookup");
-
-  if (pcb != NULL) {
-    return 1;
-  }
-  else {
-    return 1;
-  }
-}
-#endif /* LWIP_DEBUG */
 /**
  * Process an incoming UDP datagram.
  *
diff --git a/src/include/ipv4/lwip/ip.h b/src/include/ipv4/lwip/ip.h
index c631f324..c8b9c222 100644
--- a/src/include/ipv4/lwip/ip.h
+++ b/src/include/ipv4/lwip/ip.h
@@ -43,7 +43,6 @@
 struct netif;
 
 void ip_init(void);
-u8_t ip_lookup(void *header, struct netif *inp);
 struct netif *ip_route(struct ip_addr *dest);
 err_t ip_input(struct pbuf *p, struct netif *inp);
 err_t ip_output(struct pbuf *p, struct ip_addr *src, struct ip_addr *dest,
diff --git a/src/include/lwip/udp.h b/src/include/lwip/udp.h
index 8a8563c2..0b412fb0 100644
--- a/src/include/lwip/udp.h
+++ b/src/include/lwip/udp.h
@@ -91,7 +91,6 @@ err_t            udp_send       (struct udp_pcb *pcb, struct pbuf *p);
 
 
 /* The following functions are the lower layer interface to UDP. */
-u8_t             udp_lookup     (struct ip_hdr *iphdr, struct netif *inp);
 void             udp_input      (struct pbuf *p, struct netif *inp);
 void             udp_init       (void);