diff --git a/nwtests.c b/nwtests.c
index 5175474..e8bbd40 100644
--- a/nwtests.c
+++ b/nwtests.c
@@ -426,6 +426,59 @@ static int tests_nwreq87(int argc, char *argv[])
 }
 
 
+static int tests_reqtype(void)
+{
+  union REGS r;
+  struct SREGS s;
+
+  memset(&r, 0, sizeof(r));
+  memset(&s, 0, sizeof(s));
+
+  fprintf(stdout, "TEST requester type probes\n\n");
+
+  /*
+   * DeveloperNet 1997 dvlmreq.c:
+   *   AX=7A20h, BX=0, INT 2Fh
+   *   if AX==0 then ES:BX is VLM entry and client type is VLM.
+   */
+  r.x.ax = 0x7A20;
+  r.x.bx = 0;
+  int86x(0x2F, &r, &r, &s);
+
+  fprintf(stdout, "INT 2F AX=7A20 -> AX=%04X BX=%04X ES=%04X\n",
+          r.x.ax, r.x.bx, s.es);
+  if (r.x.ax == 0)
+    fprintf(stdout, "VLM entry likely present at %04X:%04X\n", s.es, r.x.bx);
+  else
+    fprintf(stdout, "VLM entry not reported by INT 2F/7A20\n");
+
+  /*
+   * DeveloperNet 1997 dvlmreq.c:
+   *   AH=DCh, CX=0, INT 21h
+   *   if CX != 0 then NETX/Shell API is present.
+   */
+  memset(&r, 0, sizeof(r));
+  memset(&s, 0, sizeof(s));
+  r.h.ah = 0xDC;
+  r.x.cx = 0;
+  int86x(0x21, &r, &r, &s);
+
+  fprintf(stdout, "INT 21 AH=DC CX=0 -> AX=%04X BX=%04X CX=%04X DX=%04X ES=%04X\n",
+          r.x.ax, r.x.bx, r.x.cx, r.x.dx, s.es);
+  if (r.x.cx != 0)
+    fprintf(stdout, "NETX/Shell API likely present\n");
+  else
+    fprintf(stdout, "NETX/Shell API not reported by AH=DC\n");
+
+  fprintf(stdout, "\nInterpretation like DeveloperNet dvlmreq.c:\n");
+  if (r.x.cx != 0)
+    fprintf(stdout, "  Shell bit present\n");
+  fprintf(stdout, "  If INT2F AX=7A20 returned AX=0000, VLM path should be used for NWCREQUEST.\n");
+
+  return(0);
+}
+
+
 int func_tests(int argc, char *argv[], int mode)
 {
   if (argc >= 2) {
@@ -435,6 +488,9 @@ int func_tests(int argc, char *argv[], int mode)
     if (tests_same_arg(argv[1], "E300") || tests_same_arg(argv[1], "NETCALLE300"))
       return tests_netcall_e300();
 
+    if (tests_same_arg(argv[1], "REQTYPE"))
+      return tests_reqtype();
+
     if (tests_same_arg(argv[1], "NWREQ87"))
       return tests_nwreq87(argc, argv);