diff --git a/cores/esp8266/LwipIntfDev.h b/cores/esp8266/LwipIntfDev.h
index 3354a32563..f8290d7cd6 100644
--- a/cores/esp8266/LwipIntfDev.h
+++ b/cores/esp8266/LwipIntfDev.h
@@ -66,6 +66,7 @@ class LwipIntfDev: public LwipIntf, public RawDev
 
     void setDefault();
 
+    // true if interface has a valid IPv4 address
     bool connected()
     {
         return !!ip4_addr_get_u32(ip_2_ip4(&_netif.ip_addr));
@@ -305,8 +306,10 @@ void LwipIntfDev<RawDev>::netif_status_callback()
 {
     if (connected())
     {
-        if (_default)
+        if (_default || (netif_default == nullptr && !ip_addr_isany(&_netif.gw)))
         {
+            // on user request,
+            // or if there is no current default interface, but a gateway is valid
             netif_set_default(&_netif);
         }
         sntp_stop();
diff --git a/tools/sdk/lib/liblwip2-1460-feat.a b/tools/sdk/lib/liblwip2-1460-feat.a
index 15667a43f1..3ed56d2c2d 100644
Binary files a/tools/sdk/lib/liblwip2-1460-feat.a and b/tools/sdk/lib/liblwip2-1460-feat.a differ
diff --git a/tools/sdk/lib/liblwip2-1460.a b/tools/sdk/lib/liblwip2-1460.a
index aaf44366c8..7de7fadeda 100644
Binary files a/tools/sdk/lib/liblwip2-1460.a and b/tools/sdk/lib/liblwip2-1460.a differ
diff --git a/tools/sdk/lib/liblwip2-536-feat.a b/tools/sdk/lib/liblwip2-536-feat.a
index 73ffe5eeed..556e864256 100644
Binary files a/tools/sdk/lib/liblwip2-536-feat.a and b/tools/sdk/lib/liblwip2-536-feat.a differ
diff --git a/tools/sdk/lib/liblwip2-536.a b/tools/sdk/lib/liblwip2-536.a
index 1b3080ff81..f9ece4cea5 100644
Binary files a/tools/sdk/lib/liblwip2-536.a and b/tools/sdk/lib/liblwip2-536.a differ
diff --git a/tools/sdk/lib/liblwip6-1460-feat.a b/tools/sdk/lib/liblwip6-1460-feat.a
index 7a1edf6d3f..f50d97d2ad 100644
Binary files a/tools/sdk/lib/liblwip6-1460-feat.a and b/tools/sdk/lib/liblwip6-1460-feat.a differ
diff --git a/tools/sdk/lib/liblwip6-536-feat.a b/tools/sdk/lib/liblwip6-536-feat.a
index c21c9fd233..fae8152112 100644
Binary files a/tools/sdk/lib/liblwip6-536-feat.a and b/tools/sdk/lib/liblwip6-536-feat.a differ
diff --git a/tools/sdk/lwip2/builder b/tools/sdk/lwip2/builder
index 7421258237..450bb63c1b 160000
--- a/tools/sdk/lwip2/builder
+++ b/tools/sdk/lwip2/builder
@@ -1 +1 @@
-Subproject commit 7421258237b7c8f61629226961af498a0a6e0096
+Subproject commit 450bb63c1bc8b35770ca7f246945cf383569f52f
diff --git a/tools/sdk/lwip2/include/glue.h b/tools/sdk/lwip2/include/glue.h
index ffe84d2625..453a3830e9 100644
--- a/tools/sdk/lwip2/include/glue.h
+++ b/tools/sdk/lwip2/include/glue.h
@@ -118,4 +118,20 @@ err_glue_t	glue2esp_linkoutput		(int netif_idx, void* ref2save, void* data, size
 #define lwip_xt_rsil(level) (__extension__({uint32_t state; __asm__ __volatile__("rsil %0," __STRINGIFY(level) : "=a" (state) :: "memory"); state;}))
 #define lwip_xt_wsr_ps(state)  __asm__ __volatile__("wsr %0,ps; isync" :: "a" (state) : "memory")
 
+// quickfix: workaround for definition of __PRI32(x) in inttypes.h
+// it has changed with recent version of xtensa-gcc
+// __INT32 is missing
+// gcc-4.x:    __PRI32(x) is __STRINGIFY(l##x)
+// gcc-10.2.0: __PRI32(x) is __INT32 __STRINGIFY(x)
+#include <inttypes.h>
+#if !defined(__INT8)
+#define __INT8
+#endif
+#if !defined(__INT16)
+#define __INT16
+#endif
+#if !defined(__INT32)
+#define __INT32 "l"
+#endif
+
 #endif // GLUE_H
diff --git a/tools/sdk/lwip2/include/lwip-git-hash.h b/tools/sdk/lwip2/include/lwip-git-hash.h
index 146c0d3110..96c8999789 100644
--- a/tools/sdk/lwip2/include/lwip-git-hash.h
+++ b/tools/sdk/lwip2/include/lwip-git-hash.h
@@ -1,5 +1,5 @@
 // generated by makefiles/make-lwip2-hash
 #ifndef LWIP_HASH_H
 #define LWIP_HASH_H
-#define LWIP_HASH_STR "STABLE-2_1_2_RELEASE/glue:1.2-48-g7421258"
+#define LWIP_HASH_STR "STABLE-2_1_3_RELEASE/glue:1.2-58-g450bb63"
 #endif // LWIP_HASH_H
diff --git a/tools/sdk/lwip2/include/lwip/debug.h b/tools/sdk/lwip2/include/lwip/debug.h
index baa6a40901..579fd242b2 100644
--- a/tools/sdk/lwip2/include/lwip/debug.h
+++ b/tools/sdk/lwip2/include/lwip/debug.h
@@ -120,9 +120,7 @@
 #endif /* LWIP_NOASSERT */
 
 #ifndef LWIP_ERROR
-#ifndef LWIP_NOASSERT
-#define LWIP_PLATFORM_ERROR(message) LWIP_PLATFORM_ASSERT(message)
-#elif defined LWIP_DEBUG
+#ifdef LWIP_DEBUG
 #define LWIP_PLATFORM_ERROR(message) LWIP_PLATFORM_DIAG((message))
 #else
 #define LWIP_PLATFORM_ERROR(message)
diff --git a/tools/sdk/lwip2/include/lwip/if_api.h b/tools/sdk/lwip2/include/lwip/if_api.h
index 39017abd32..b7269e2a62 100644
--- a/tools/sdk/lwip2/include/lwip/if_api.h
+++ b/tools/sdk/lwip2/include/lwip/if_api.h
@@ -49,7 +49,9 @@
 extern "C" {
 #endif
 
+#ifndef IF_NAMESIZE
 #define IF_NAMESIZE NETIF_NAMESIZE
+#endif
 
 char * lwip_if_indextoname(unsigned int ifindex, char *ifname);
 unsigned int lwip_if_nametoindex(const char *ifname);
diff --git a/tools/sdk/lwip2/include/lwip/init.h b/tools/sdk/lwip2/include/lwip/init.h
index a149be1848..6cabfc8fd4 100644
--- a/tools/sdk/lwip2/include/lwip/init.h
+++ b/tools/sdk/lwip2/include/lwip/init.h
@@ -54,7 +54,7 @@ extern "C" {
 /** x.X.x: Minor version of the stack */
 #define LWIP_VERSION_MINOR      1
 /** x.x.X: Revision of the stack */
-#define LWIP_VERSION_REVISION   2
+#define LWIP_VERSION_REVISION   3
 /** For release candidates, this is set to 1..254
   * For official releases, this is set to 255 (LWIP_RC_RELEASE)
   * For development versions (Git), this is set to 0 (LWIP_RC_DEVELOPMENT) */
diff --git a/tools/sdk/lwip2/include/lwip/netif.h b/tools/sdk/lwip2/include/lwip/netif.h
index c29a987610..89ab85d256 100644
--- a/tools/sdk/lwip2/include/lwip/netif.h
+++ b/tools/sdk/lwip2/include/lwip/netif.h
@@ -386,6 +386,10 @@ struct netif {
 #if LWIP_LOOPBACK_MAX_PBUFS
   u16_t loop_cnt_current;
 #endif /* LWIP_LOOPBACK_MAX_PBUFS */
+#if LWIP_NETIF_LOOPBACK_MULTITHREADING
+  /* Used if the original scheduling failed. */
+  u8_t reschedule_poll;
+#endif /* LWIP_NETIF_LOOPBACK_MULTITHREADING */
 #endif /* ENABLE_LOOPBACK */
 #if LWIP_IPV4 && IP_NAPT
   u8_t napt;
@@ -454,7 +458,7 @@ void netif_set_gw(struct netif *netif, const ip4_addr_t *gw);
 
 #define netif_set_flags(netif, set_flags)     do { (netif)->flags = (u8_t)((netif)->flags |  (set_flags)); } while(0)
 #define netif_clear_flags(netif, clr_flags)   do { (netif)->flags = (u8_t)((netif)->flags & (u8_t)(~(clr_flags) & 0xff)); } while(0)
-#define netif_is_flag_set(nefif, flag)        (((netif)->flags & (flag)) != 0)
+#define netif_is_flag_set(netif, flag)        (((netif)->flags & (flag)) != 0)
 
 void netif_set_up(struct netif *netif);
 void netif_set_down(struct netif *netif);
diff --git a/tools/sdk/lwip2/include/lwip/opt.h b/tools/sdk/lwip2/include/lwip/opt.h
index 371286b6ab..410e3fffdd 100644
--- a/tools/sdk/lwip2/include/lwip/opt.h
+++ b/tools/sdk/lwip2/include/lwip/opt.h
@@ -1549,7 +1549,7 @@
  * TCP_MSS, IP header, and link header.
  */
 #if !defined PBUF_POOL_BUFSIZE || defined __DOXYGEN__
-#define PBUF_POOL_BUFSIZE               LWIP_MEM_ALIGN_SIZE(TCP_MSS+40+PBUF_LINK_ENCAPSULATION_HLEN+PBUF_LINK_HLEN)
+#define PBUF_POOL_BUFSIZE               LWIP_MEM_ALIGN_SIZE(TCP_MSS+PBUF_IP_HLEN+PBUF_TRANSPORT_HLEN+PBUF_LINK_ENCAPSULATION_HLEN+PBUF_LINK_HLEN)
 #endif
 
 /**
@@ -1559,6 +1559,14 @@
 #if !defined LWIP_PBUF_REF_T || defined __DOXYGEN__
 #define LWIP_PBUF_REF_T                 u8_t
 #endif
+
+/**
+ * LWIP_PBUF_CUSTOM_DATA: Store private data on pbufs (e.g. timestamps)
+ * This extends struct pbuf so user can store custom data on every pbuf.
+ */
+#if !defined LWIP_PBUF_CUSTOM_DATA || defined __DOXYGEN__
+#define LWIP_PBUF_CUSTOM_DATA
+#endif
 /**
  * @}
  */
@@ -1916,11 +1924,8 @@
 
 /** LWIP_NETCONN_FULLDUPLEX==1: Enable code that allows reading from one thread,
  * writing from a 2nd thread and closing from a 3rd thread at the same time.
- * ATTENTION: This is currently really alpha! Some requirements:
- * - LWIP_NETCONN_SEM_PER_THREAD==1 is required to use one socket/netconn from
- *   multiple threads at once
- * - sys_mbox_free() has to unblock receive tasks waiting on recvmbox/acceptmbox
- *   and prevent a task pending on this during/after deletion
+ * LWIP_NETCONN_SEM_PER_THREAD==1 is required to use one socket/netconn from
+ * multiple threads at once!
  */
 #if !defined LWIP_NETCONN_FULLDUPLEX || defined __DOXYGEN__
 #define LWIP_NETCONN_FULLDUPLEX         0
@@ -2450,7 +2455,7 @@
  * network startup.
  */
 #if !defined LWIP_IPV6_SEND_ROUTER_SOLICIT || defined __DOXYGEN__
-#define LWIP_IPV6_SEND_ROUTER_SOLICIT   1
+#define LWIP_IPV6_SEND_ROUTER_SOLICIT   LWIP_IPV6
 #endif
 
 /**
@@ -2495,10 +2500,12 @@
 
 /**
  * LWIP_ICMP6_DATASIZE: bytes from original packet to send back in
- * ICMPv6 error messages.
+ * ICMPv6 error messages (0 = default of IP6_MIN_MTU_LENGTH)
+ * ATTENTION: RFC4443 section 2.4 says IP6_MIN_MTU_LENGTH is a MUST,
+ * so override this only if you absolutely have to!
  */
 #if !defined LWIP_ICMP6_DATASIZE || defined __DOXYGEN__
-#define LWIP_ICMP6_DATASIZE             8
+#define LWIP_ICMP6_DATASIZE             0
 #endif
 
 /**
diff --git a/tools/sdk/lwip2/include/lwip/pbuf.h b/tools/sdk/lwip2/include/lwip/pbuf.h
index 82902a4e98..e5daf968e8 100644
--- a/tools/sdk/lwip2/include/lwip/pbuf.h
+++ b/tools/sdk/lwip2/include/lwip/pbuf.h
@@ -219,6 +219,9 @@ struct pbuf {
 
   /** For incoming packets, this contains the input netif's index */
   u8_t if_idx;
+
+  /** In case the user needs to store data custom data on a pbuf */
+  LWIP_PBUF_CUSTOM_DATA
 };
 
 
@@ -293,6 +296,7 @@ void pbuf_cat(struct pbuf *head, struct pbuf *tail);
 void pbuf_chain(struct pbuf *head, struct pbuf *tail);
 struct pbuf *pbuf_dechain(struct pbuf *p);
 err_t pbuf_copy(struct pbuf *p_to, const struct pbuf *p_from);
+err_t pbuf_copy_partial_pbuf(struct pbuf *p_to, const struct pbuf *p_from, u16_t copy_len, u16_t offset);
 u16_t pbuf_copy_partial(const struct pbuf *p, void *dataptr, u16_t len, u16_t offset);
 void *pbuf_get_contiguous(const struct pbuf *p, void *buffer, size_t bufsize, u16_t len, u16_t offset);
 err_t pbuf_take(struct pbuf *buf, const void *dataptr, u16_t len);
diff --git a/tools/sdk/lwip2/include/lwip/priv/altcp_priv.h b/tools/sdk/lwip2/include/lwip/priv/altcp_priv.h
index 2d3b2fdbce..d1de9b111b 100644
--- a/tools/sdk/lwip2/include/lwip/priv/altcp_priv.h
+++ b/tools/sdk/lwip2/include/lwip/priv/altcp_priv.h
@@ -85,6 +85,11 @@ typedef err_t (*altcp_get_tcp_addrinfo_fn)(struct altcp_pcb *conn, int local, ip
 typedef ip_addr_t *(*altcp_get_ip_fn)(struct altcp_pcb *conn, int local);
 typedef u16_t (*altcp_get_port_fn)(struct altcp_pcb *conn, int local);
 
+#if LWIP_TCP_KEEPALIVE
+typedef void  (*altcp_keepalive_disable_fn)(struct altcp_pcb *conn);
+typedef void  (*altcp_keepalive_enable_fn)(struct altcp_pcb *conn, u32_t idle, u32_t intvl, u32_t count);
+#endif
+
 #ifdef LWIP_DEBUG
 typedef enum tcp_state (*altcp_dbg_get_tcp_state_fn)(struct altcp_pcb *conn);
 #endif
@@ -111,6 +116,10 @@ struct altcp_functions {
   altcp_get_tcp_addrinfo_fn   addrinfo;
   altcp_get_ip_fn             getip;
   altcp_get_port_fn           getport;
+#if LWIP_TCP_KEEPALIVE
+  altcp_keepalive_disable_fn  keepalive_disable;
+  altcp_keepalive_enable_fn   keepalive_enable;
+#endif
 #ifdef LWIP_DEBUG
   altcp_dbg_get_tcp_state_fn  dbg_get_tcp_state;
 #endif
@@ -133,6 +142,10 @@ void  altcp_default_dealloc(struct altcp_pcb *conn);
 err_t altcp_default_get_tcp_addrinfo(struct altcp_pcb *conn, int local, ip_addr_t *addr, u16_t *port);
 ip_addr_t *altcp_default_get_ip(struct altcp_pcb *conn, int local);
 u16_t altcp_default_get_port(struct altcp_pcb *conn, int local);
+#if LWIP_TCP_KEEPALIVE
+void  altcp_default_keepalive_disable(struct altcp_pcb *conn);
+void  altcp_default_keepalive_enable(struct altcp_pcb *conn, u32_t idle, u32_t intvl, u32_t count);
+#endif
 #ifdef LWIP_DEBUG
 enum tcp_state altcp_default_dbg_get_tcp_state(struct altcp_pcb *conn);
 #endif
diff --git a/tools/sdk/lwip2/include/lwip/prot/icmp6.h b/tools/sdk/lwip2/include/lwip/prot/icmp6.h
index 3461120421..36989f6b32 100644
--- a/tools/sdk/lwip2/include/lwip/prot/icmp6.h
+++ b/tools/sdk/lwip2/include/lwip/prot/icmp6.h
@@ -146,6 +146,8 @@ PACK_STRUCT_END
 #  include "arch/epstruct.h"
 #endif
 
+#define ICMP6_HLEN 8
+
 /** This is the ICMP6 header adapted for echo req/resp. */
 #ifdef PACK_STRUCT_USE_INCLUDES
 #  include "arch/bpstruct.h"
diff --git a/tools/sdk/lwip2/include/lwip/prot/ip6.h b/tools/sdk/lwip2/include/lwip/prot/ip6.h
index 0f6de45593..7df81edd69 100644
--- a/tools/sdk/lwip2/include/lwip/prot/ip6.h
+++ b/tools/sdk/lwip2/include/lwip/prot/ip6.h
@@ -44,6 +44,8 @@
 extern "C" {
 #endif
 
+#define IP6_MIN_MTU_LENGTH 1280
+
 /** This is the packed version of ip6_addr_t,
     used in network headers that are itself packed */
 #ifdef PACK_STRUCT_USE_INCLUDES
diff --git a/tools/sdk/lwip2/include/lwipopts.h b/tools/sdk/lwip2/include/lwipopts.h
index d4dc179558..508245e6c0 100644
--- a/tools/sdk/lwip2/include/lwipopts.h
+++ b/tools/sdk/lwip2/include/lwipopts.h
@@ -1557,7 +1557,7 @@
  * TCP_MSS, IP header, and link header.
  */
 #if !defined PBUF_POOL_BUFSIZE || defined __DOXYGEN__
-#define PBUF_POOL_BUFSIZE               LWIP_MEM_ALIGN_SIZE(TCP_MSS+40+PBUF_LINK_ENCAPSULATION_HLEN+PBUF_LINK_HLEN)
+#define PBUF_POOL_BUFSIZE               LWIP_MEM_ALIGN_SIZE(TCP_MSS+PBUF_IP_HLEN+PBUF_TRANSPORT_HLEN+PBUF_LINK_ENCAPSULATION_HLEN+PBUF_LINK_HLEN)
 #endif
 
 /**
@@ -1567,6 +1567,14 @@
 #ifndef LWIP_PBUF_REF_T
 #define LWIP_PBUF_REF_T                 u8_t
 #endif
+
+/**
+ * LWIP_PBUF_CUSTOM_DATA: Store private data on pbufs (e.g. timestamps)
+ * This extends struct pbuf so user can store custom data on every pbuf.
+ */
+#if !defined LWIP_PBUF_CUSTOM_DATA || defined __DOXYGEN__
+#define LWIP_PBUF_CUSTOM_DATA
+#endif
 /**
  * @}
  */
@@ -1924,11 +1932,8 @@
 
 /** LWIP_NETCONN_FULLDUPLEX==1: Enable code that allows reading from one thread,
  * writing from a 2nd thread and closing from a 3rd thread at the same time.
- * ATTENTION: This is currently really alpha! Some requirements:
- * - LWIP_NETCONN_SEM_PER_THREAD==1 is required to use one socket/netconn from
- *   multiple threads at once
- * - sys_mbox_free() has to unblock receive tasks waiting on recvmbox/acceptmbox
- *   and prevent a task pending on this during/after deletion
+ * LWIP_NETCONN_SEM_PER_THREAD==1 is required to use one socket/netconn from
+ * multiple threads at once!
  */
 #if !defined LWIP_NETCONN_FULLDUPLEX || defined __DOXYGEN__
 #define LWIP_NETCONN_FULLDUPLEX         0
@@ -2464,7 +2469,7 @@
  * network startup.
  */
 #if !defined LWIP_IPV6_SEND_ROUTER_SOLICIT || defined __DOXYGEN__
-#define LWIP_IPV6_SEND_ROUTER_SOLICIT   1
+#define LWIP_IPV6_SEND_ROUTER_SOLICIT   LWIP_IPV6
 #endif
 
 /**
@@ -2509,10 +2514,12 @@
 
 /**
  * LWIP_ICMP6_DATASIZE: bytes from original packet to send back in
- * ICMPv6 error messages.
+ * ICMPv6 error messages (0 = default of IP6_MIN_MTU_LENGTH)
+ * ATTENTION: RFC4443 section 2.4 says IP6_MIN_MTU_LENGTH is a MUST,
+ * so override this only if you absolutely have to!
  */
 #if !defined LWIP_ICMP6_DATASIZE || defined __DOXYGEN__
-#define LWIP_ICMP6_DATASIZE             8
+#define LWIP_ICMP6_DATASIZE             0
 #endif
 
 /**
@@ -3547,6 +3554,11 @@
    --------------------------------------------------
 */
 
+#include "lwip/debug.h"
+#include "arch/cc.h"
+#include "lwip-git-hash.h"
+#include <sys/time.h> // settimeofday() + struct timeval
+
 #ifndef LWIP_FEATURES
 #error LWIP_FEATURES must be defined
 #endif
@@ -3584,6 +3596,19 @@ extern void lwip_hook_dhcp_parse_option(struct netif *netif, struct dhcp *dhcp,
                                         int msg_type, int option, int option_len, struct pbuf *pbuf,
                                         int option_value_offset);
 
+#if LWIP_FEATURES
+#define LWIP_HOOK_DHCP_APPEND_OPTIONS(netif, dhcp, state, msg, msg_type, option_len_ptr) { \
+   /* https://github.com/esp8266/Arduino/issues/8223 */ \
+   lwip_hook_dhcp_amend_options(netif, dhcp, state, msg, msg_type, option_len_ptr); \
+   /* https://github.com/esp8266/Arduino/issues/8247 */ \
+   if ((msg_type) == DHCP_DISCOVER) \
+      *(option_len_ptr) = dhcp_option_hostname(*(option_len_ptr), (msg)->options, netif); \
+}
+
+extern void lwip_hook_dhcp_amend_options(struct netif *netif, struct dhcp *dhcp, int state, struct dhcp_msg *msg,
+                                         int msg_type, u16 *option_len_ptr);
+#endif
+
 /*
    --------------------------------------------------
    ------------------ SNTP options ------------------
@@ -3629,11 +3654,6 @@ uint32_t SNTP_STARTUP_DELAY_FUNC;
    --------------------------------------------------
 */
 
-#include "lwip/debug.h"
-#include "arch/cc.h"
-#include "lwip-git-hash.h"
-#include <sys/time.h> // settimeofday() + struct timeval
-
 // allow to handle special packets (user redefinable)
 struct pbuf;
 struct netif;
diff --git a/tools/sdk/lwip2/include/netif/ppp/ppp_opts.h b/tools/sdk/lwip2/include/netif/ppp/ppp_opts.h
index 6702bec618..479a006d10 100644
--- a/tools/sdk/lwip2/include/netif/ppp/ppp_opts.h
+++ b/tools/sdk/lwip2/include/netif/ppp/ppp_opts.h
@@ -44,6 +44,13 @@
 #define PPPOE_SUPPORT                   0
 #endif
 
+/**
+ * PPPOE_SCNAME_SUPPORT==1: Enable PPP Over Ethernet Service Name and Concentrator Name support
+ */
+#ifndef PPPOE_SCNAME_SUPPORT
+#define PPPOE_SCNAME_SUPPORT            0
+#endif
+
 /**
  * PPPOL2TP_SUPPORT==1: Enable PPP Over L2TP
  */