diff --git a/docs/add_rtadv.md b/docs/add_rtadv.md
index 1020c5e..cc92410 100644
--- a/docs/add_rtadv.md
+++ b/docs/add_rtadv.md
@@ -7,12 +7,12 @@
 ## Synopsis
 
 ```
-add_rtadv ${card} ${vlan}
+add_rtadv ${interface}
 ```
 
 ## Description
 
-Adds the network defined by the specified `${card}` and `${vlan}` to the list of
+Adds the network defined by the specified `${interface}` to the list of
 interfaces to be advertised by `rtadvd`.  
 
 The internal implementation prevents adding duplicate interfaces to the
@@ -29,8 +29,8 @@ settings for all advertised IPv6 networks.
 ## Examples
 
 ```
-add_rtadv xy0 123 # Adds `xy0.123` to `rtadvd_interfaces`
-add_rtadv abc3 765 # Adds `abc3.765` to `rtadvd_interfaces`
+add_rtadv xy0.123 # Adds `xy0.123` to `rtadvd_interfaces`
+add_rtadv abc3.765 # Adds `abc3.765` to `rtadvd_interfaces`
 ```
 
 ## See Also
diff --git a/rc.subr b/rc.subr
index 2684ab9..7f9d997 100755
--- a/rc.subr
+++ b/rc.subr
@@ -133,8 +133,8 @@ _compute_nets()
     shift 1
 
     _base=$((${_vlan}%10))
-    _net=$((${_vlan}/100))
-    _subnet=${_net}${_base}
+    _net=$(( ( ( ${_vlan} / 100 ) % 10 ) * 10 ))
+    _subnet=$(( ${_net} + ${_base} ))
     _extra_address=""
 
     if [ -z "${1}" ]
@@ -203,10 +203,7 @@ add_vlan()
 
 add_rtadv()
 {
-    _card=$1
-    _vlan=$2
-
-    _subcard="${_card}.${_vlan}"
+    _subcard="$1"
 
     _echo "XXX ${rtadvd_interfaces} XXX"
     _echo "QQQ ${rtadvd_interfaces} QQQ" | grep ${_subcard}
@@ -462,15 +459,23 @@ _emit_dhcpv4()
 add_v4_net()
 {
     _compute_nets $*
-    add_vlan $_card $_vlan
+	_card_and_vlan="${_card}_${_vlan}"
+	_card_dot_vlan="${_card}.${_vlan}"
+    if [ ${_vlan} -ne 0 ]
+	then
+		add_vlan $_card $_vlan
+	else
+		_card_and_vlan="${_card}"
+		_card_dot_vlan="${_card}"
+	fi
 
     _class_group=""
     if [ ! -z "${_class}" ]
     then
         _class_group="group ${_class}"
     fi
-    eval ifconfig_${_card}_${_vlan}=\"$(compute_v4_net $_card $_subnet) group internal ${_class_group}\"
-    eval dhcpd_ifaces=\"${dhcpd_ifaces} ${_card}.${_vlan}\"
+    eval ifconfig_${_card_and_vlan}=\"$(compute_v4_net $_card $_subnet) group internal ${_class_group}\"
+    eval dhcpd_ifaces=\"${dhcpd_ifaces} ${_card_dot_vlan}\"
 }
 
 _add_v6_prefixes()
@@ -480,7 +485,7 @@ _add_v6_prefixes()
 
     while [ -n "${1}" ]
     do
-        eval ifconfig_${_card}_${_vlan}_alias${_next_alias}=\"inet6 $1/64\"
+        eval ifconfig_${_card_and_vlan}_alias${_next_alias}=\"inet6 $1/64\"
         shift 1
         _next_alias=`expr $_next_alias + 1`
     done
@@ -490,8 +495,16 @@ add_v6_net()
 {
 	_isp=""
     _compute_nets $*
-    add_vlan $_card $_vlan
-    add_rtadv $_card $_vlan
+	_card_and_vlan="${_card}_${_vlan}"
+	_card_dot_vlan="${_card}.${_vlan}"
+    if [ ${_vlan} -ne 0 ]
+	then
+		add_vlan $_card $_vlan
+	else
+		_card_and_vlan="${_card}"
+		_card_dot_vlan="${_card}"
+	fi
+    add_rtadv ${_card_dot_vlan}
 
 	_compute_ula_prefix
 
@@ -501,22 +514,27 @@ add_v6_net()
         _class_group="group ${_class}"
     fi
 
-    eval ifconfig_${_card}_${_vlan}_ipv6=\"inet6 fe80::1/64 group internal ${_class_group}\"
+    eval ifconfig_${_card_and_vlan}_ipv6=\"inet6 fe80::1/64 group internal ${_class_group}\"
 
     _next_alias=0
 
+	if [ "${_subnet}" = "0" ]
+	then
+		_subnet="00"
+	fi
+
     if [ "${_priv}" = "YES" ]
     then
-        eval ifconfig_${_card}_${_vlan}_alias${_next_alias}=\"inet6 $(compute_v6_net ${secret_ip6_net} ${_subnet})/64\"
+        eval ifconfig_${_card_and_vlan}_alias${_next_alias}=\"inet6 $(compute_v6_net ${secret_ip6_net} ${_subnet})/64\"
         _next_alias=1 # UGLY HACK!!!  Does BASH increment work in BSD's sh?
     fi
 
     if [ -n "${_isp}" ]
     then
-        _add_dhcpv6 ${_card}.${_vlan} ${_isp}
+        _add_dhcpv6 ${_card_dot_vlan} ${_isp}
 	else
-		_echo "Adding ${_card}.${_vlan} to default (which is ${default_isp} at this time)"
-        _add_dhcpv6 ${_card}.${_vlan} default
+		_echo "Adding ${_card_dot_vlan} to default (which is ${default_isp} at this time)"
+        _add_dhcpv6 ${_card_dot_vlan} default
     fi
 
     _add_v6_prefixes ${_next_alias} ${_extra_address}