How to make dhclient run when wlan0 is brought back up (but already has an old address)

With the following configuration on Devuan Chimaera Linux: /etc/network/interfaces auto wlan0 iface wlan0 inet dhcp pre-up /sbin/wpa_supplicant -B -Dwext -i wlan0 -c /etc/wpa_supplicant/wpa_supplicant.conf post-down /usr/bin/killall -q wpa_supplicant /etc/wpa_supplicant/wpa_supplicant.conf network={ ssid="MySSID" psk="redacted" } ctrl_interface=/run/wpa_supplicant update_config=1 dhclient only runs when the interface first comes up. If I use ifconfig wlan0 down, the IP address is retained while down and ifconfig wlan0 up brings the interface back up without running dhclient. Unfortunately I have a custom /etc/dhcp/dhclient-exit-hooks.d/wlan0-routes which adds custom routes, calculated from the default route provided by dhclient. When I bring wlan0 down, the custom routes are lost, as expected. When I bring wlan0 up, dhclient does not run and so the custom routes are not re-added. --- Update: There seems to be a difference in the behaviour of ifconfig wlan0 down (which caused this) and ifdown wlan0. root@demo:~# ifconfig wlan0 down root@demo:~# ip addr show wlan0 9: wlan0: mtu 1500 qdisc noqueue state DOWN group default qlen 1000 link/ether 00:0e:8e:4c:f6:a3 brd ff:ff:ff:ff:ff:ff inet 192.168.98.196/24 brd 192.168.98.255 scope global dynamic wlan0 valid_lft 7130sec preferred_lft 7130sec root@demo5:~# ifconfig wlan0 up ... root@demo5:~# ifdown wlan0 root@demo5:~# ip addr show wlan0 9: wlan0: mtu 1500 qdisc noqueue state DOWN group default qlen 1000 link/ether 00:0e:8e:4c:f6:a3 brd ff:ff:ff:ff:ff:ff When I use ifdown wlan0 instead of ifconfig wlan0 down dhclient is called when I bring the interface up, and everything works as it ought. What is the difference between ifconfig wlan0 down and ifdown wlan0?