diff --git a/arch/sim/src/sim/sim_internal.h b/arch/sim/src/sim/sim_internal.h
index cb5cccdb146..c62b78d5382 100644
--- a/arch/sim/src/sim/sim_internal.h
+++ b/arch/sim/src/sim/sim_internal.h
@@ -42,6 +42,16 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
+/* Determine master-slave relationship when configuring with multiple cores */
+
+#ifdef CONFIG_RPTUN
+#  define SIM_RPTUN_MASTER (1 << 0)  /* As the master */
+#  define SIM_RPTUN_SLAVE  (0 << 0)  /* As the slave */
+
+#  define SIM_RPTUN_BOOT   (1 << 1)  /* As the master and boot the slave  */
+#  define SIM_RPTUN_NOBOOT (0 << 1)  /* As the master but not boot the slave */
+#endif
+
 #ifndef CONFIG_SMP_NCPUS
 #  define CONFIG_SMP_NCPUS 1
 #endif
@@ -362,7 +372,7 @@ void sim_netdriver_loop(void);
 /* sim_rptun.c **************************************************************/
 
 #ifdef CONFIG_RPTUN
-int sim_rptun_init(const char *shmemname, const char *cpuname, bool master);
+int sim_rptun_init(const char *shmemname, const char *cpuname, int master);
 #endif
 
 /* sim_hcisocket.c **********************************************************/
diff --git a/arch/sim/src/sim/sim_rptun.c b/arch/sim/src/sim/sim_rptun.c
index df35dae7cb3..b88f05de7dc 100644
--- a/arch/sim/src/sim/sim_rptun.c
+++ b/arch/sim/src/sim/sim_rptun.c
@@ -59,7 +59,7 @@ struct sim_rptun_dev_s
   struct rptun_dev_s        rptun;
   rptun_callback_t          callback;
   void                     *arg;
-  bool                      master;
+  int                       master;
   unsigned int              seq;
   struct sim_rptun_shmem_s *shmem;
   struct simple_addrenv_s   addrenv[2];
@@ -179,13 +179,17 @@ static int sim_rptun_start(struct rptun_dev_s *dev)
                             struct sim_rptun_dev_s, rptun);
   pid_t pid;
 
-  pid = host_posix_spawn(sim_rptun_get_cpuname(dev), NULL, NULL);
-  if (pid < 0)
+  if (priv->master & SIM_RPTUN_BOOT)
     {
-      return pid;
+      pid = host_posix_spawn(sim_rptun_get_cpuname(dev), NULL, NULL);
+      if (pid < 0)
+        {
+          return pid;
+        }
+
+      priv->pid = pid;
     }
 
-  priv->pid = pid;
   return 0;
 }
 
@@ -194,12 +198,15 @@ static int sim_rptun_stop(struct rptun_dev_s *dev)
   struct sim_rptun_dev_s *priv = container_of(dev,
                               struct sim_rptun_dev_s, rptun);
 
-  priv->shmem->cmdm = SIM_RPTUN_STOP << SIM_RPTUN_SHIFT;
+  if (priv->master & SIM_RPTUN_BOOT)
+    {
+      priv->shmem->cmdm = SIM_RPTUN_STOP << SIM_RPTUN_SHIFT;
 
-  host_waitpid(priv->pid);
+      host_waitpid(priv->pid);
 
-  host_freeshmem(priv->shmem);
-  priv->shmem = NULL;
+      host_freeshmem(priv->shmem);
+      priv->shmem = NULL;
+    }
 
   return 0;
 }
@@ -321,7 +328,7 @@ static const struct rptun_ops_s g_sim_rptun_ops =
  * Public Functions
  ****************************************************************************/
 
-int sim_rptun_init(const char *shmemname, const char *cpuname, bool master)
+int sim_rptun_init(const char *shmemname, const char *cpuname, int master)
 {
   struct sim_rptun_dev_s *dev;
   int ret;
diff --git a/boards/sim/sim/sim/src/sim_bringup.c b/boards/sim/sim/sim/src/sim_bringup.c
index 057180a3c33..b7c13435462 100644
--- a/boards/sim/sim/sim/src/sim_bringup.c
+++ b/boards/sim/sim/sim/src/sim_bringup.c
@@ -463,9 +463,10 @@ int sim_bringup(void)
 
 #ifdef CONFIG_RPTUN
 #ifdef CONFIG_SIM_RPTUN_MASTER
-  sim_rptun_init("server-proxy", "proxy", true);
+  sim_rptun_init("server-proxy", "proxy",
+                 SIM_RPTUN_MASTER | SIM_RPTUN_NOBOOT);
 #else
-  sim_rptun_init("server-proxy", "server", false);
+  sim_rptun_init("server-proxy", "server", SIM_RPTUN_SLAVE);
 #endif
 
 #ifdef CONFIG_DEV_RPMSG