Debian Configuration :: Always Need To Run Dhclient Manually For Connection

My network configuration is in a weird situation, that I always need to run dhclient manually each time after a network connection is established. When my computer connects to a router, sometimes it won't get a valid IP, and it uses an automatically generated fake Internet IP. In this situation, it won't connect to the Internet at all. Sometimes it get a valid local network IP, but still cannot connect to WAN, and could only connect to my router's address (both through ping and through router's management webpage). In both situation, it can be solved by a simple dhclient run.

This is my /etc/network/interfaces file:

Code: Select all# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet dhcp
iface wlan0 inet dhcp

and this is my /etc/NetworkManager/NetworkManager.conf:

Code: Select all[main]
plugins=ifupdown,keyfile
dhcp=dhclient
#no-auto-default=FE:50:52:BE:46:4C,