Al parecer hay un bug aqui explica que hay que compilar
https://dev.openwrt.org/ticket/16898Thanks for the hint. I tried both on DD-WRT and Ubuntu with the same config file and find no issue to connect to the server.
It led me to check the Makefile of openvpn in OpenWRT. Finally I fount the root cause of the issue. There is a mistake in Makefile of openvpn. The CONFIGURATION_VARS has a line "NETSTAT=/sbin/netstat" which should be "NETSTAT=/bin/netstat"
After the modification, the IP address can be obtained successfully. And in the log, there is a line indicates "Mon Jun 30 12:53:10 2014 PUSH: Received control message: 'PUSH_REPLY,ping 3,ping-restart 10,ifconfig 10.211.1.13 10.211.1.14,dhcp-option DNS 10.211.254.254,dhcp-option DNS 8.8.8.8,route-gateway 10.211.1.14,redirect-gateway def1'"
Hay que cambiar la letra s en donde despues de NETSTAT=......
¿ Como puedo arreglarlo ?