diff --git a/doc/ipv6.texi b/doc/ipv6.texi
index de067e0..d4ef45a 100644
--- a/doc/ipv6.texi
+++ b/doc/ipv6.texi
@@ -62,23 +62,24 @@
 @end itemize
 @end deffn
 
-@deffn {Interface Command} {ipv6 nd ra-interval SECONDS} {}
-@deffnx {Interface Command} {no ipv6 nd ra-interval} {}
+@deffn {Interface Command} {ipv6 nd ra-interval <1-1800>} {}
+@deffnx {Interface Command} {no ipv6 nd ra-interval [<1-1800>]} {}
 The  maximum  time allowed between sending unsolicited multicast router
-advertisements from the interface, in seconds. Must be no less than 3 seconds.
+advertisements from the interface, in seconds.
 
 Default: @code{600}
 @end deffn
 
-@deffn {Interface Command} {ipv6 nd ra-interval msec MILLISECONDS} {}
-@deffnx {Interface Command} {no ipv6 nd ra-interval msec} {}
+@deffn {Interface Command} {ipv6 nd ra-interval msec <70-1800000>} {}
+@deffnx {Interface Command} {no ipv6 nd ra-interval [msec <70-1800000>]} {}
 The  maximum  time allowed between sending unsolicited multicast router
-advertisements from the interface, in milliseconds. Must be no less than 30 milliseconds.
+advertisements from the interface, in milliseconds.
 
 Default: @code{600000}
 @end deffn
-@deffn {Interface Command} {ipv6 nd ra-lifetime SECONDS} {}
-@deffnx {Interface Command} {no ipv6 nd ra-lifetime} {}
+
+@deffn {Interface Command} {ipv6 nd ra-lifetime <0-9000>} {}
+@deffnx {Interface Command} {no ipv6 nd ra-lifetime [<0-9000>]} {}
 The value to be placed in the Router Lifetime field of router advertisements
 sent from the interface, in seconds. Indicates the usefulness of the router
 as a default router on this interface. Setting the value to zero indicates
@@ -89,12 +90,12 @@
 Default: @code{1800}
 @end deffn
 
-@deffn {Interface Command} {ipv6 nd reachable-time MILLISECONDS} {}
-@deffnx {Interface Command} {no ipv6 nd reachable-time} {}
+@deffn {Interface Command} {ipv6 nd reachable-time <1-3600000>} {}
+@deffnx {Interface Command} {no ipv6 nd reachable-time [<1-3600000>]} {}
 The value to be placed in the Reachable Time field in the Router Advertisement
 messages sent by the router, in milliseconds. The configured time enables the
 router to detect unavailable neighbors. The value zero means unspecified (by
-this router). Must be no greater than @code{3,600,000} milliseconds (1 hour).
+this router).
 
 Default: @code{0}
 @end deffn
@@ -126,18 +127,20 @@
 Default: not set
 @end deffn
 
-@deffn {Interface Command} {ipv6 nd home-agent-preference} {}
-@deffnx {Interface Command} {no ipv6 nd home-agent-preference} {}
+@deffn {Interface Command} {ipv6 nd home-agent-preference <0-65535>} {}
+@deffnx {Interface Command} {no ipv6 nd home-agent-preference [<0-65535>]} {}
 The value to be placed in Home Agent Option, when Home Agent config flag is set, 
-which indicates to hosts Home Agent preference.
+which indicates to hosts Home Agent preference. The default value of 0 stands
+for the lowest preference possible.
 
 Default: 0
 @end deffn
 
-@deffn {Interface Command} {ipv6 nd home-agent-lifetime} {}
-@deffnx {Interface Command} {no ipv6 nd home-agent-lifetime} {}
++@deffn {Interface Command} {ipv6 nd home-agent-lifetime <0-65520>} {}
++@deffnx {Interface Command} {no ipv6 nd home-agent-lifetime [<0-65520>]} {}
 The value to be placed in Home Agent Option, when Home Agent config flag is set, 
-which indicates to hosts Home Agent Lifetime. A value of 0 means to place Router Lifetime value.
+which indicates to hosts Home Agent Lifetime. The default value of 0 means to
+place the current Router Lifetime value.
 
 Default: 0
 @end deffn
@@ -151,7 +154,7 @@
 @end deffn
 
 @deffn {Interface Command} {ipv6 nd router-preference (high|medium|low)} {}
-@deffnx {Interface Command} {no ipv6 nd router-preference} {}
+@deffnx {Interface Command} {no ipv6 nd router-preference [(high|medium|low)]} {}
 Set default router preference in IPv6 router advertisements per RFC4191.
 
 Default: medium
diff --git a/zebra/rtadv.c b/zebra/rtadv.c
index c6c3b03..ae5c5a1 100644
--- a/zebra/rtadv.c
+++ b/zebra/rtadv.c
@@ -723,30 +723,22 @@
 
 DEFUN (ipv6_nd_ra_interval_msec,
        ipv6_nd_ra_interval_msec_cmd,
-       "ipv6 nd ra-interval msec MILLISECONDS",
+       "ipv6 nd ra-interval msec <70-1800000>",
        "Interface IPv6 config commands\n"
        "Neighbor discovery\n"
        "Router Advertisement interval\n"
        "Router Advertisement interval in milliseconds\n")
 {
-  int interval;
-  struct interface *ifp;
-  struct zebra_if *zif;
+  unsigned interval;
+  struct interface *ifp = (struct interface *) vty->index;
+  struct zebra_if *zif = ifp->info;
 
-  ifp = (struct interface *) vty->index;
-  zif = ifp->info;
-
-  interval = atoi (argv[0]);
-
-  if
-  (
-    interval < 70 || interval > 1800000 ||
-    (zif->rtadv.AdvDefaultLifetime != -1 && interval > zif->rtadv.AdvDefaultLifetime * 1000)
-  )
-    {
-      vty_out (vty, "Invalid Router Advertisement Interval%s", VTY_NEWLINE);
-      return CMD_WARNING;
-    }
+  VTY_GET_INTEGER_RANGE ("router advertisement interval", interval, argv[0], 70, 1800000);
+  if ((zif->rtadv.AdvDefaultLifetime != -1 && interval > (unsigned)zif->rtadv.AdvDefaultLifetime * 1000))
+  {
+    vty_out (vty, "This ra-interval would conflict with configured ra-lifetime!%s", VTY_NEWLINE);
+    return CMD_WARNING;
+  }
 
   if (zif->rtadv.MaxRtrAdvInterval % 1000)
     rtadv->adv_msec_if_count--;
@@ -763,30 +755,22 @@
 
 DEFUN (ipv6_nd_ra_interval,
        ipv6_nd_ra_interval_cmd,
-       "ipv6 nd ra-interval SECONDS",
+       "ipv6 nd ra-interval <1-1800>",
        "Interface IPv6 config commands\n"
        "Neighbor discovery\n"
        "Router Advertisement interval\n"
        "Router Advertisement interval in seconds\n")
 {
-  int interval;
-  struct interface *ifp;
-  struct zebra_if *zif;
+  unsigned interval;
+  struct interface *ifp = (struct interface *) vty->index;
+  struct zebra_if *zif = ifp->info;
 
-  ifp = (struct interface *) vty->index;
-  zif = ifp->info;
-
-  interval = atoi (argv[0]);
-
-  if
-  (
-    interval < 1 || interval > 1800 ||
-    (zif->rtadv.AdvDefaultLifetime != -1 && interval > zif->rtadv.AdvDefaultLifetime)
-  )
-    {
-      vty_out (vty, "Invalid Router Advertisement Interval%s", VTY_NEWLINE);
-      return CMD_WARNING;
-    }
+  VTY_GET_INTEGER_RANGE ("router advertisement interval", interval, argv[0], 1, 1800);
+  if ((zif->rtadv.AdvDefaultLifetime != -1 && interval > (unsigned)zif->rtadv.AdvDefaultLifetime))
+  {
+    vty_out (vty, "This ra-interval would conflict with configured ra-lifetime!%s", VTY_NEWLINE);
+    return CMD_WARNING;
+  }
 
   if (zif->rtadv.MaxRtrAdvInterval % 1000)
     rtadv->adv_msec_if_count--;
@@ -825,13 +809,30 @@
   return CMD_SUCCESS;
 }
 
+ALIAS (no_ipv6_nd_ra_interval,
+       no_ipv6_nd_ra_interval_val_cmd,
+       "no ipv6 nd ra-interval <1-1800>",
+       NO_STR
+       "Interface IPv6 config commands\n"
+       "Neighbor discovery\n"
+       "Router Advertisement interval\n")
+
+ALIAS (no_ipv6_nd_ra_interval,
+       no_ipv6_nd_ra_interval_msec_val_cmd,
+       "no ipv6 nd ra-interval msec <1-1800000>",
+       NO_STR
+       "Interface IPv6 config commands\n"
+       "Neighbor discovery\n"
+       "Router Advertisement interval\n"
+       "Router Advertisement interval in milliseconds\n")
+
 DEFUN (ipv6_nd_ra_lifetime,
        ipv6_nd_ra_lifetime_cmd,
-       "ipv6 nd ra-lifetime SECONDS",
+       "ipv6 nd ra-lifetime <0-9000>",
        "Interface IPv6 config commands\n"
        "Neighbor discovery\n"
        "Router lifetime\n"
-       "Router lifetime in seconds\n")
+       "Router lifetime in seconds (0 stands for a non-default gw)\n")
 {
   int lifetime;
   struct interface *ifp;
@@ -840,19 +841,15 @@
   ifp = (struct interface *) vty->index;
   zif = ifp->info;
 
-  lifetime = atoi (argv[0]);
+  VTY_GET_INTEGER_RANGE ("router lifetime", lifetime, argv[0], 0, 9000);
 
   /* The value to be placed in the Router Lifetime field
    * of Router Advertisements sent from the interface,
    * in seconds.  MUST be either zero or between
    * MaxRtrAdvInterval and 9000 seconds. -- RFC4861, 6.2.1 */
-  if
-  (
-    lifetime > RTADV_MAX_RTRLIFETIME ||
-    (lifetime != 0 && lifetime * 1000 < zif->rtadv.MaxRtrAdvInterval)
-  )
+  if ((lifetime != 0 && lifetime * 1000 < zif->rtadv.MaxRtrAdvInterval))
     {
-      vty_out (vty, "Invalid Router Lifetime%s", VTY_NEWLINE);
+      vty_out (vty, "This ra-lifetime would conflict with configured ra-interval%s", VTY_NEWLINE);
       return CMD_WARNING;
     }
 
@@ -880,31 +877,26 @@
   return CMD_SUCCESS;
 }
 
+ALIAS (no_ipv6_nd_ra_lifetime,
+       no_ipv6_nd_ra_lifetime_val_cmd,
+       "no ipv6 nd ra-lifetime <0-9000>",
+       NO_STR
+       "Interface IPv6 config commands\n"
+       "Neighbor discovery\n"
+       "Router lifetime\n"
+       "Router lifetime in seconds (0 stands for a non-default gw)\n")
+
 DEFUN (ipv6_nd_reachable_time,
        ipv6_nd_reachable_time_cmd,
-       "ipv6 nd reachable-time MILLISECONDS",
+       "ipv6 nd reachable-time <1-3600000>",
        "Interface IPv6 config commands\n"
        "Neighbor discovery\n"
        "Reachable time\n"
        "Reachable time in milliseconds\n")
 {
-  u_int32_t rtime;
-  struct interface *ifp;
-  struct zebra_if *zif;
-
-  ifp = (struct interface *) vty->index;
-  zif = ifp->info;
-
-  rtime = (u_int32_t) atol (argv[0]);
-
-  if (rtime > RTADV_MAX_REACHABLE_TIME)
-    {
-      vty_out (vty, "Invalid Reachable time%s", VTY_NEWLINE);
-      return CMD_WARNING;
-    }
-
-  zif->rtadv.AdvReachableTime = rtime;
-
+  struct interface *ifp = (struct interface *) vty->index;
+  struct zebra_if *zif = ifp->info;
+  VTY_GET_INTEGER_RANGE ("reachable time", zif->rtadv.AdvReachableTime, argv[0], 1, RTADV_MAX_REACHABLE_TIME);
   return CMD_SUCCESS;
 }
 
@@ -927,31 +919,26 @@
   return CMD_SUCCESS;
 }
 
+ALIAS (no_ipv6_nd_reachable_time,
+       no_ipv6_nd_reachable_time_val_cmd,
+       "no ipv6 nd reachable-time <1-3600000>",
+       NO_STR
+       "Interface IPv6 config commands\n"
+       "Neighbor discovery\n"
+       "Reachable time\n"
+       "Reachable time in milliseconds\n")
+
 DEFUN (ipv6_nd_homeagent_preference,
        ipv6_nd_homeagent_preference_cmd,
-       "ipv6 nd home-agent-preference PREFERENCE",
+       "ipv6 nd home-agent-preference <0-65535>",
        "Interface IPv6 config commands\n"
        "Neighbor discovery\n"
        "Home Agent preference\n"
-       "Home Agent preference value 0..65535\n")
+       "preference value (default is 0, least preferred)\n")
 {
-  u_int32_t hapref;
-  struct interface *ifp;
-  struct zebra_if *zif;
-
-  ifp = (struct interface *) vty->index;
-  zif = ifp->info;
-
-  hapref = (u_int32_t) atol (argv[0]);
-
-  if (hapref > 65535)
-    {
-      vty_out (vty, "Invalid Home Agent preference%s", VTY_NEWLINE);
-      return CMD_WARNING;
-    }
-
-  zif->rtadv.HomeAgentPreference = hapref;
-
+  struct interface *ifp = (struct interface *) vty->index;
+  struct zebra_if *zif = ifp->info;
+  VTY_GET_INTEGER_RANGE ("home agent preference", zif->rtadv.HomeAgentPreference, argv[0], 0, 65535);
   return CMD_SUCCESS;
 }
 
@@ -974,31 +961,26 @@
   return CMD_SUCCESS;
 }
 
+ALIAS (no_ipv6_nd_homeagent_preference,
+       no_ipv6_nd_homeagent_preference_val_cmd,
+       "no ipv6 nd home-agent-preference <0-65535>",
+       NO_STR
+       "Interface IPv6 config commands\n"
+       "Neighbor discovery\n"
+       "Home Agent preference\n"
+       "preference value (default is 0, least preferred)\n")
+
 DEFUN (ipv6_nd_homeagent_lifetime,
        ipv6_nd_homeagent_lifetime_cmd,
-       "ipv6 nd home-agent-lifetime SECONDS",
+       "ipv6 nd home-agent-lifetime <0-65520>",
        "Interface IPv6 config commands\n"
        "Neighbor discovery\n"
        "Home Agent lifetime\n"
-       "Home Agent lifetime in seconds\n")
+       "Home Agent lifetime in seconds (0 to track ra-lifetime)\n")
 {
-  u_int32_t ha_ltime;
-  struct interface *ifp;
-  struct zebra_if *zif;
-
-  ifp = (struct interface *) vty->index;
-  zif = ifp->info;
-
-  ha_ltime = (u_int32_t) atol (argv[0]);
-
-  if (ha_ltime < 1 || ha_ltime > RTADV_MAX_HALIFETIME)
-    {
-      vty_out (vty, "Invalid Home Agent Lifetime time%s", VTY_NEWLINE);
-      return CMD_WARNING;
-    }
-
-  zif->rtadv.HomeAgentLifetime = ha_ltime;
-
+  struct interface *ifp = (struct interface *) vty->index;
+  struct zebra_if *zif = ifp->info;
+  VTY_GET_INTEGER_RANGE ("home agent lifetime", zif->rtadv.HomeAgentLifetime, argv[0], 0, RTADV_MAX_HALIFETIME);
   return CMD_SUCCESS;
 }
 
@@ -1021,6 +1003,15 @@
   return CMD_SUCCESS;
 }
 
+ALIAS (no_ipv6_nd_homeagent_lifetime,
+       no_ipv6_nd_homeagent_lifetime_val_cmd,
+       "no ipv6 nd home-agent-lifetime <0-65520>",
+       NO_STR
+       "Interface IPv6 config commands\n"
+       "Neighbor discovery\n"
+       "Home Agent lifetime\n"
+       "Home Agent lifetime in seconds (0 to track ra-lifetime)\n")
+
 DEFUN (ipv6_nd_managed_config_flag,
        ipv6_nd_managed_config_flag_cmd,
        "ipv6 nd managed-config-flag",
@@ -1490,6 +1481,17 @@
   return CMD_SUCCESS;
 }
 
+ALIAS (no_ipv6_nd_router_preference,
+       no_ipv6_nd_router_preference_val_cmd,
+       "no ipv6 nd router-preference (high|medium|low",
+       NO_STR
+       "Interface IPv6 config commands\n"
+       "Neighbor discovery\n"
+       "Default router preference\n"
+       "High default router preference\n"
+       "Low default router preference\n"
+       "Medium default router preference (default)\n")
+
 DEFUN (ipv6_nd_mtu,
        ipv6_nd_mtu_cmd,
        "ipv6 nd mtu <1-65535>",
@@ -1686,10 +1688,14 @@
   install_element (INTERFACE_NODE, &ipv6_nd_ra_interval_cmd);
   install_element (INTERFACE_NODE, &ipv6_nd_ra_interval_msec_cmd);
   install_element (INTERFACE_NODE, &no_ipv6_nd_ra_interval_cmd);
+  install_element (INTERFACE_NODE, &no_ipv6_nd_ra_interval_val_cmd);
+  install_element (INTERFACE_NODE, &no_ipv6_nd_ra_interval_msec_val_cmd);
   install_element (INTERFACE_NODE, &ipv6_nd_ra_lifetime_cmd);
   install_element (INTERFACE_NODE, &no_ipv6_nd_ra_lifetime_cmd);
+  install_element (INTERFACE_NODE, &no_ipv6_nd_ra_lifetime_val_cmd);
   install_element (INTERFACE_NODE, &ipv6_nd_reachable_time_cmd);
   install_element (INTERFACE_NODE, &no_ipv6_nd_reachable_time_cmd);
+  install_element (INTERFACE_NODE, &no_ipv6_nd_reachable_time_val_cmd);
   install_element (INTERFACE_NODE, &ipv6_nd_managed_config_flag_cmd);
   install_element (INTERFACE_NODE, &no_ipv6_nd_managed_config_flag_cmd);
   install_element (INTERFACE_NODE, &ipv6_nd_other_config_flag_cmd);
@@ -1698,8 +1704,10 @@
   install_element (INTERFACE_NODE, &no_ipv6_nd_homeagent_config_flag_cmd);
   install_element (INTERFACE_NODE, &ipv6_nd_homeagent_preference_cmd);
   install_element (INTERFACE_NODE, &no_ipv6_nd_homeagent_preference_cmd);
+  install_element (INTERFACE_NODE, &no_ipv6_nd_homeagent_preference_val_cmd);
   install_element (INTERFACE_NODE, &ipv6_nd_homeagent_lifetime_cmd);
   install_element (INTERFACE_NODE, &no_ipv6_nd_homeagent_lifetime_cmd);
+  install_element (INTERFACE_NODE, &no_ipv6_nd_homeagent_lifetime_val_cmd);
   install_element (INTERFACE_NODE, &ipv6_nd_adv_interval_config_option_cmd);
   install_element (INTERFACE_NODE, &no_ipv6_nd_adv_interval_config_option_cmd);
   install_element (INTERFACE_NODE, &ipv6_nd_prefix_cmd);
@@ -1719,6 +1727,7 @@
   install_element (INTERFACE_NODE, &no_ipv6_nd_prefix_cmd);
   install_element (INTERFACE_NODE, &ipv6_nd_router_preference_cmd);
   install_element (INTERFACE_NODE, &no_ipv6_nd_router_preference_cmd);
+  install_element (INTERFACE_NODE, &no_ipv6_nd_router_preference_val_cmd);
   install_element (INTERFACE_NODE, &ipv6_nd_mtu_cmd);
   install_element (INTERFACE_NODE, &no_ipv6_nd_mtu_cmd);
   install_element (INTERFACE_NODE, &no_ipv6_nd_mtu_val_cmd);