diff --git a/tools/tunslip6.c b/tools/tunslip6.c
index 75659e270..3029eb536 100644
--- a/tools/tunslip6.c
+++ b/tools/tunslip6.c
@@ -62,7 +62,7 @@ const char *netmask;
 int slipfd = 0;
 uint16_t basedelay=0,delaymsec=0;
 uint32_t startsec,startmsec,delaystartsec,delaystartmsec;
-int timestamp = 0, flowcontrol=0, showprogress=0;
+int timestamp = 0, flowcontrol=0, showprogress=0, flowcontrol_xonxoff=0;
 
 int ssystem(const char *fmt, ...)
      __attribute__((__format__ (__printf__, 1, 2)));
@@ -75,6 +75,10 @@ void slip_send_char(int fd, unsigned char c);
 
 char tundev[1024] = { "" };
 
+/* IPv6 required minimum MTU */
+#define MIN_DEVMTU 1500
+int devmtu = MIN_DEVMTU;
+
 int
 ssystem(const char *fmt, ...) __attribute__((__format__ (__printf__, 1, 2)));
 
@@ -91,11 +95,15 @@ ssystem(const char *fmt, ...)
   return system(cmd);
 }
 
-#define SLIP_END     0300
-#define SLIP_ESC     0333
-#define SLIP_ESC_END 0334
-#define SLIP_ESC_ESC 0335
+#define SLIP_END      0300
+#define SLIP_ESC      0333
+#define SLIP_ESC_END  0334
+#define SLIP_ESC_ESC  0335
 
+#define SLIP_ESC_XON  0336
+#define SLIP_ESC_XOFF 0337
+#define XON           17
+#define XOFF          19
 
 /* get sockaddr, IPv4 or IPv6: */
 void *
@@ -287,6 +295,12 @@ serial_to_tun(FILE *inslip, int outfd)
     case SLIP_ESC_ESC:
       c = SLIP_ESC;
       break;
+    case SLIP_ESC_XON:
+      c = XON;
+      break;
+    case SLIP_ESC_XOFF:
+      c = XOFF;
+      break;
     }
     /* FALLTHROUGH */
   default:
@@ -330,6 +344,22 @@ slip_send_char(int fd, unsigned char c)
     slip_send(fd, SLIP_ESC);
     slip_send(fd, SLIP_ESC_ESC);
     break;
+  case XON:
+    if(flowcontrol_xonxoff) {
+      slip_send(fd, SLIP_ESC);
+      slip_send(fd, SLIP_ESC_XON);
+    } else {
+      slip_send(fd, c);
+    }
+    break;
+  case XOFF:
+    if(flowcontrol_xonxoff) {
+      slip_send(fd, SLIP_ESC);
+      slip_send(fd, SLIP_ESC_XOFF);
+    } else {
+      slip_send(fd, c);
+    }
+    break;
   default:
     slip_send(fd, c);
     break;
@@ -415,6 +445,22 @@ write_to_serial(int outfd, void *inbuf, int len)
       slip_send(outfd, SLIP_ESC);
       slip_send(outfd, SLIP_ESC_ESC);
       break;
+    case XON:
+      if(flowcontrol_xonxoff) {
+        slip_send(outfd, SLIP_ESC);
+        slip_send(outfd, SLIP_ESC_XON);
+      } else {
+        slip_send(outfd, p[i]);
+      }
+      break;
+    case XOFF:
+      if(flowcontrol_xonxoff) {
+        slip_send(outfd, SLIP_ESC);
+        slip_send(outfd, SLIP_ESC_XOFF);
+      } else {
+        slip_send(outfd, p[i]);
+      }
+      break;
     default:
       slip_send(outfd, p[i]);
       break;
@@ -467,6 +513,12 @@ stty_telos(int fd)
     tty.c_cflag |= CRTSCTS;
   else
     tty.c_cflag &= ~CRTSCTS;
+  tty.c_iflag &= ~IXON;
+  if(flowcontrol_xonxoff) {
+    tty.c_iflag |= IXOFF | IXANY;
+  } else {
+    tty.c_iflag &= ~IXOFF & ~IXANY;
+  }
   tty.c_cflag &= ~HUPCL;
   tty.c_cflag &= ~CLOCAL;
 
@@ -609,7 +661,7 @@ ifconf(const char *tundev, const char *ipaddr)
 {
 #ifdef linux
   if (timestamp) stamptime();
-  ssystem("ifconfig %s inet `hostname` up", tundev);
+  ssystem("ifconfig %s inet `hostname` mtu %d up", tundev, devmtu);
   if (timestamp) stamptime();
   ssystem("ifconfig %s add %s", tundev, ipaddr);
 
@@ -670,7 +722,7 @@ ifconf(const char *tundev, const char *ipaddr)
 		prefix = "64";
 	}
     if (timestamp) stamptime();
-    ssystem("ifconfig %s inet6 up", tundev );
+    ssystem("ifconfig %s inet6 mtu %d up", tundev, devmtu);
     if (timestamp) stamptime();
     ssystem("ifconfig %s inet6 %s add", tundev, ipaddr );
     if (timestamp) stamptime();
@@ -679,7 +731,7 @@ ifconf(const char *tundev, const char *ipaddr)
   }
 #else
   if (timestamp) stamptime();
-  ssystem("ifconfig %s inet `hostname` %s up", tundev, ipaddr);
+  ssystem("ifconfig %s inet `hostname` %s mtu %d up", tundev, ipaddr, devmtu);
   if (timestamp) stamptime();
   ssystem("sysctl -w net.inet.ip.forwarding=1");
 #endif /* !linux */
@@ -708,7 +760,7 @@ main(int argc, char **argv)
   prog = argv[0];
   setvbuf(stdout, NULL, _IOLBF, 0); /* Line buffered output. */
 
-  while((c = getopt(argc, argv, "B:HILPhs:t:v::d::a:p:T")) != -1) {
+  while((c = getopt(argc, argv, "B:HILPhXM:s:t:v::d::a:p:T")) != -1) {
     switch(c) {
     case 'B':
       baudrate = atoi(optarg);
@@ -718,10 +770,20 @@ main(int argc, char **argv)
       flowcontrol=1;
       break;
 
+    case 'X':
+      flowcontrol_xonxoff=1;
+      break;
+
     case 'L':
       timestamp=1;
       break;
 
+    case 'M':
+      devmtu=atoi(optarg);
+      if(devmtu < MIN_DEVMTU) {
+        devmtu = MIN_DEVMTU;
+      }
+
     case 'P':
       showprogress=1;
       break;
@@ -782,8 +844,10 @@ fprintf(stderr," -B baudrate    9600,19200,38400,57600,115200 (default),230400\n
 #endif
 fprintf(stderr," -H             Hardware CTS/RTS flow control (default disabled)\n");
 fprintf(stderr," -I             Inquire IP address\n");
+fprintf(stderr," -X             Software XON/XOFF flow control (default disabled)\n");
 fprintf(stderr," -L             Log output format (adds time stamps)\n");
 fprintf(stderr," -s siodev      Serial device (default /dev/ttyUSB0)\n");
+fprintf(stderr," -M             Interface MTU (default and min: 1280)\n");
 fprintf(stderr," -T             Make tap interface (default is tun interface)\n");
 fprintf(stderr," -t tundev      Name of interface (default tap0 or tun0)\n");
 fprintf(stderr," -v[level]      Verbosity level\n");
@@ -836,9 +900,18 @@ exit(1);
   case 460800:
     b_rate = B460800;
     break;
+  case 500000:
+    b_rate = B500000;
+    break;
+  case 576000:
+    b_rate = B576000;
+    break;
   case 921600:
     b_rate = B921600;
     break;
+  case 1000000:
+    b_rate = B1000000;
+    break;
 #endif
   default:
     err(1, "unknown baudrate %d", baudrate);