После запуска сервера.
$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         ip-172-31-16-1. 0.0.0.0         UG    0      0        0 eth0
ip-10-4-0-2.us- *               255.255.255.255 UH    0      0        0 tun1
172.31.16.0     *               255.255.240.0   U     0      0        0 eth0

Конфиг сервера:
$ cat /etc/openvpn/openvpn.conf
port 1194
proto tcp-server
dev tun1
ifconfig 10.4.0.1 10.4.0.2
status server-tcp.log
verb 3
secret ovpn.key

Конфиг клиента:
$ cat openvpn.client.ovpn
proto tcp-client
remote 52.15.118.78
port 1194
dev tun
secret "/home/taomao/OpenVPNconf/ovpn.key"
redirect-gateway def1
ifconfig 10.4.0.2 10.4.0.1