diff --git a/libexec/rc/rc.conf b/libexec/rc/rc.conf
--- a/libexec/rc/rc.conf
+++ b/libexec/rc/rc.conf
@@ -501,7 +501,8 @@
 #netwait_if=""			# Wait for active link on each intf in this list.
 netwait_if_timeout="30"		# Total number of seconds to monitor link state.
 netwait_dad="NO"		# Wait for DAD to complete
-netwait_dad_timeout="10"	# Total number of seconds to wait for DAD.
+netwait_dad_timeout=""		# Total number of seconds to wait for DAD, zero
+				# or unset to autodetect
 
 ### Miscellaneous network options: ###
 icmp_bmcastecho="NO"	# respond to broadcast ping packets
diff --git a/libexec/rc/rc.d/netwait b/libexec/rc/rc.d/netwait
--- a/libexec/rc/rc.d/netwait
+++ b/libexec/rc/rc.d/netwait
@@ -36,13 +36,15 @@
 		err 1 "Nothing to wait for"
 	fi
 
-	if ! [ "${netwait_if_timeout}" -ge 1 ]; then
+	if ! [ "${netwait_if_timeout:=0}" -ge 1 ]; then
 		err 1 "netwait_if_timeout must be >= 1"
 	fi
-	if ! [ "${netwait_dad_timeout}" -ge 1 ]; then
-		err 1 "netwait_dad_timeout must be >= 1"
+	if ! check_kern_features inet6; then
+		netwait_dad="NO"
+	elif ! [ "${netwait_dad_timeout:=0}" -ge 1 ]; then
+		netwait_dad_timeout=$(($(sysctl -n net.inet6.ip6.dad_count)+1))
 	fi
-	if ! [ "${netwait_timeout}" -ge 1 ]; then
+	if ! [ "${netwait_timeout:=0}" -ge 1 ]; then
 		err 1 "netwait_timeout must be >= 1"
 	fi
 
diff --git a/share/man/man5/rc.conf.5 b/share/man/man5/rc.conf.5
--- a/share/man/man5/rc.conf.5
+++ b/share/man/man5/rc.conf.5
@@ -22,7 +22,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd October 2, 2025
+.Dd October 5, 2025
 .Dt RC.CONF 5
 .Os
 .Sh NAME
@@ -4618,8 +4618,11 @@
 to enable waiting for DAD to complete.
 .It Va netwait_dad_timeout
 .Pq Vt int
-Indicates the total number of seconds to wait for DAD to complete.
-The default is 10.
+Unset by default.
+Indicates the maximum number of seconds to wait for DAD to complete.
+If zero or unset, the timeout will be one more than the value of the
+.Va net.inet6.ip6.dad_count
+sysctl variable.
 .It Va rctl_enable
 .Pq Vt bool
 If set to