diff --git a/toxcore/LAN_discovery.c b/toxcore/LAN_discovery.c
index 0f237cca..eadec9ec 100644
--- a/toxcore/LAN_discovery.c
+++ b/toxcore/LAN_discovery.c
@@ -176,6 +176,11 @@ int LAN_ip(IP ip)
                 && ip4.uint8[2] != 255)
             return 0;
 
+        /* RFC 6598: 100.64.0.0 to 100.127.255.255 (100.64.0.0/10)
+         * (shared address space to stack another layer of NAT) */
+        if ((ip4.uint8[0] == 100) && ((ip4.uint8[1] & 0xC0) == 0x40))
+            return 0;
+
     } else if (ip.family == AF_INET6) {
 
         /* autogenerated for each interface: FE80::* (up to FEBF::*)