If you’ve configured Dropbear (the SSH server) for OpenWRT so that it has a secondary listener for your WAN port (you may want to do this if you want the WAN SSH listener on a different port from the default), then you’ve probably noticed that it doesn’t come up on its own after your WAN link drops.
There’s a really easy solution to this. Configure hotplug.d so that when your WAN interface bounces, dropbear gets restarted! Put this into /etc/hotplug.d/iface/40-dropbear ;
#!/bin/sh if [ "$INTERFACE" = "wan" ] && [ "$ACTION" = "ifup" ] then /etc/init.d/dropbear restart fi
This tip was found at the bottom of the documentation for Dropbear listed above.