Index: etc/netstart
===================================================================
RCS file: /cvs/src/etc/netstart,v
retrieving revision 1.190
diff -u -p -r1.190 netstart
--- etc/netstart	10 Feb 2018 08:46:10 -0000	1.190
+++ etc/netstart	14 Mar 2018 00:09:12 -0000
@@ -62,6 +62,9 @@ parse_hn_line() {
 		_cmds[${#_cmds[*]}]="ifconfig $_if ${_c[@]} down;dhclient $_if"
 		V4_DHCPCONF=true
 		;;
+	down)	_c[0]=
+		_ifup=down
+		;;
 	'!'*)	_cmd=$(print -- "${_c[@]}" | sed 's/\$if/'$_if'/g')
 		_cmds[${#_cmds[*]}]="${_cmd#!}"
 		;;
@@ -77,6 +80,7 @@ parse_hn_line() {
 ifstart() {
 	local _if=$1 _hn=/etc/hostname.$1 _cmds _i=0 _line _stat
 	set -A _cmds
+	_ifup=up
 
 	# Interface names must be alphanumeric only.  We check to avoid
 	# configuring backup or temp files, and to catch the "*" case.
@@ -107,6 +111,8 @@ ifstart() {
 	while IFS= read -- _line; do
 		parse_hn_line $_line
 	done <$_hn
+
+	_cmds[${#_cmds[*]}]="ifconfig $_if $_ifup"
 
 	# Apply the interface configuration commands stored in _cmds array.
 	while ((_i < ${#_cmds[*]})); do
Index: share/man/man5/hostname.if.5
===================================================================
RCS file: /cvs/src/share/man/man5/hostname.if.5,v
retrieving revision 1.65
diff -u -p -r1.65 hostname.if.5
--- share/man/man5/hostname.if.5	10 Mar 2017 18:28:11 -0000	1.65
+++ share/man/man5/hostname.if.5	14 Mar 2018 00:09:12 -0000
@@ -57,6 +57,9 @@ the administrator should not expect magi
 and the
 per-driver manual pages to see what arguments are permitted.
 .Pp
+Interfaces are implicitly configured to be brought up and running.
+This behaviour can be disabled by adding a line containing down to the file.
+.Pp
 Arguments containing either whitespace or single quote
 characters must be double quoted.
 For example: