diff --git a/ports/c16x/include/arch/cc.h b/ports/c16x/include/arch/cc.h
index 480a6b3..e330958 100644
--- a/ports/c16x/include/arch/cc.h
+++ b/ports/c16x/include/arch/cc.h
@@ -20,6 +20,14 @@ typedef signed     long    s32_t;
 
 typedef u32_t mem_ptr_t;
 
+/* Define (sn)printf formatters for these lwIP types */
+#define U16_F "hu"
+#define S16_F "hd"
+#define X16_F "hx"
+#define U32_F "lu"
+#define S32_F "ld"
+#define X32_F "lx"
+
 /* LW: Supported in at least >=v7.5 r2, but lwIP worked without the "_packed" attribute already */
 #define PACK_STRUCT_BEGIN _packed
 #define PACK_STRUCT_STRUCT
diff --git a/ports/c16x/include/netif/cs8900if.h b/ports/c16x/include/netif/cs8900if.h
index 41e3417..1c74027 100644
--- a/ports/c16x/include/netif/cs8900if.h
+++ b/ports/c16x/include/netif/cs8900if.h
@@ -75,6 +75,6 @@ void cs8900if_service(struct netif *);
 void cs8900if_input(struct netif *netif);
 err_t cs8900if_output(struct netif *netif, struct pbuf *p, struct ip_addr *ipaddr);
 
-void cs8900_send_debug(unsigned char *p, unsigned int len);
+void cs8900_send_debug(u8_t *p, u16_t len);
 
 #endif /* __NETIF_CS8900IF_H__ */
diff --git a/ports/c16x/netif/cs8900if.c b/ports/c16x/netif/cs8900if.c
index 7197275..c12b7bd 100644
--- a/ports/c16x/netif/cs8900if.c
+++ b/ports/c16x/netif/cs8900if.c
@@ -142,7 +142,7 @@ static const struct eth_addr ethbroadcast = {{0xffU,0xffU,0xffU,0xffU,0xffU,0xff
 static err_t cs8900_output(struct netif *netif, struct pbuf *p);
 static struct pbuf *cs8900_input(struct netif *netif);
 static void cs8900_service(struct netif *netif);
-static u32_t cs8900_chksum(void *dataptr, int len);
+static u32_t cs8900_chksum(void *dataptr, s16_t len);
 static void cs8900_reset(struct netif *netif);
 
 // Define these to match your hardware setup
@@ -320,7 +320,7 @@ static err_t cs8900_init(struct netif *netif)
  */
 static err_t cs8900_output(struct netif *netif, struct pbuf *p)
 {
-  int tries = 0;
+  s16_t tries = 0;
   err_t result;
 
   // exit if link has failed
@@ -352,7 +352,7 @@ static err_t cs8900_output(struct netif *netif, struct pbuf *p)
   // ready to transmit?
   if ((PPDATA & 0x0100U/*Rdy4TxNOW*/) != 0)
   {
-  	unsigned long sent_bytes = 0;
+    u32_t sent_bytes = 0;
     /* q traverses through linked list of pbuf's
      * This list MUST consist of a single packet ONLY */
     struct pbuf *q;
@@ -440,7 +440,7 @@ static struct pbuf *cs8900_input(struct netif *netif)
     event_type = 0;
     // read RxLength
     len = RXTXREG;
-    LWIP_DEBUGF(NETIF_DEBUG, ("cs8900_input: packet len %u\n", len));
+    LWIP_DEBUGF(NETIF_DEBUG, ("cs8900_input: packet len %"U16_F"\n", len));
     snmp_add_ifinoctets(len);
     // positive length?
     if (len > 0)
@@ -456,7 +456,7 @@ static struct pbuf *cs8900_input(struct netif *netif)
 
         for (q = p; q != 0; q = q->next)
         {
-	        LWIP_DEBUGF(NETIF_DEBUG, ("cs8900_input: pbuf @%p tot_len %u len %u\n", q, q->tot_len, q->len));
+	        LWIP_DEBUGF(NETIF_DEBUG, ("cs8900_input: pbuf @%p tot_len %"U16_F" len %"U16_F"\n", q, q->tot_len, q->len));
 	        ptr = q->payload;
           // TODO: CHECK: what if q->len is odd? we don't use the last byte?
           for (i = 0; i < (q->len + 1) / 2; i++)
@@ -509,9 +509,9 @@ static struct pbuf *cs8900_input(struct netif *netif)
 static void cs8900_service(struct netif *netif)
 {
   /* amount of ISQ's to handle (> 0) in one cs8900_service() call */
-  unsigned char events2service = 1;
+  u8_t events2service = 1;
 #if (CS8900_STATS > 0)
-  unsigned int miss_count = 0, coll_count = 0;
+  u16_t miss_count = 0, coll_count = 0;
 #endif
   // NOTES:
   // static, so only initialized to zero at program start.
@@ -595,10 +595,10 @@ static void cs8900_service(struct netif *netif)
 #if (CS8900_STATS > 0)
   /* copy statistics counters into netif state fields */
   ((struct cs8900if *)netif->state)->missed += miss_count;
-  if (miss_count > 0) LWIP_DEBUGF(NETIF_DEBUG | 1, ("cs8900_input: %u missed packets due to rx buffer overrun\n", miss_count));
+  if (miss_count > 0) LWIP_DEBUGF(NETIF_DEBUG | 1, ("cs8900_input: %"U16_F" missed packets due to rx buffer overrun\n", miss_count));
 
   ((struct cs8900if *)netif->state)->collisions += coll_count;
-  if (coll_count > 0) LWIP_DEBUGF(NETIF_DEBUG | 1, ("cs8900_input: %u packet collisions\n", coll_count)); 
+  if (coll_count > 0) LWIP_DEBUGF(NETIF_DEBUG | 1, ("cs8900_input: %"U16_F" packet collisions\n", coll_count)); 
 #endif
 }
 
@@ -776,9 +776,9 @@ err_t cs8900if_init(struct netif *netif)
  * @param p pointer to an array of bytes, at least with length 'len'
  * @param len number of bytes available at the address pointed to by 'p'
  */
-void cs8900_send_debug(unsigned char *p, unsigned int len)
+void cs8900_send_debug(u8_t *p, u16_t len)
 {
-  int tries = 0, i;
+  s16_t tries = 0, i;
 
   // network interface state
   extern struct netif *ethif;
@@ -887,7 +887,7 @@ void cs8900_send_debug(unsigned char *p, unsigned int len)
   }
 }
 
-static u32_t cs8900_chksum(void *dataptr, int len)
+static u32_t cs8900_chksum(void *dataptr, s16_t len)
 {
   u32_t acc = 0;
   u16_t *ptr = (u16_t *)dataptr;
diff --git a/ports/unix/include/arch/cc.h b/ports/unix/include/arch/cc.h
index fcf5961..5de2ec8 100644
--- a/ports/unix/include/arch/cc.h
+++ b/ports/unix/include/arch/cc.h
@@ -50,6 +50,14 @@ typedef signed     long    s32_t;
 
 typedef u32_t mem_ptr_t;
 
+/* Define (sn)printf formatters for these lwIP types */
+#define U16_F "hu"
+#define S16_F "hd"
+#define X16_F "hx"
+#define U32_F "lu"
+#define S32_F "ld"
+#define X32_F "lx"
+
 /* Compiler hints for packing structures */
 #define PACK_STRUCT_FIELD(x) x __attribute__((packed))
 #define PACK_STRUCT_STRUCT __attribute__((packed))
diff --git a/ports/unix/proj/unixsim/Makefile b/ports/unix/proj/unixsim/Makefile
index f3db66f..ddf5aff 100644
--- a/ports/unix/proj/unixsim/Makefile
+++ b/ports/unix/proj/unixsim/Makefile
@@ -54,7 +54,7 @@ CFLAGS:=$(CFLAGS) \
 COREFILES=$(LWIPDIR)/core/mem.c $(LWIPDIR)/core/memp.c $(LWIPDIR)/core/netif.c \
 	$(LWIPDIR)/core/pbuf.c $(LWIPDIR)/core/raw.c $(LWIPDIR)/core/stats.c \
 	$(LWIPDIR)/core/sys.c $(LWIPDIR)/core/tcp.c $(LWIPDIR)/core/tcp_in.c \
-        $(LWIPDIR)/core/tcp_out.c $(LWIPDIR)/core/udp.c 
+        $(LWIPDIR)/core/tcp_out.c $(LWIPDIR)/core/udp.c $(LWIPDIR)/core/dhcp.c
 CORE4FILES=$(wildcard $(LWIPDIR)/core/ipv4/*.c) $(LWIPDIR)/core/inet.c
 
 
diff --git a/ports/unix/proj/unixsim/lwipopts.h b/ports/unix/proj/unixsim/lwipopts.h
index 9dc341d..315adce 100644
--- a/ports/unix/proj/unixsim/lwipopts.h
+++ b/ports/unix/proj/unixsim/lwipopts.h
@@ -188,8 +188,7 @@ a lot of data that needs to be copied, this should be set high. */
 
 /* ---------- DHCP options ---------- */
 /* Define LWIP_DHCP to 1 if you want DHCP configuration of
-   interfaces. DHCP is not implemented in lwIP 0.5.1, however, so
-   turning this on does currently not work. */
+   interfaces. */
 #define LWIP_DHCP               0
 
 /* 1 if you want to do an ARP check on the offered address
diff --git a/ports/unix/proj/unixsim/simhost.c b/ports/unix/proj/unixsim/simhost.c
index 8471c46..9278d9d 100644
--- a/ports/unix/proj/unixsim/simhost.c
+++ b/ports/unix/proj/unixsim/simhost.c
@@ -320,7 +320,6 @@ main_thread(void *arg)
     netif_add(&netif, &ipaddr, &netmask, &gw, NULL, tapif_init,
 		      tcpip_input);
     netif_set_default(&netif);
-    dhcp_init();
     dhcp_start(&netif);
   }
 #else