无法从外部计算机SSH到Devstack实例

I have a strange problem ever since I installed devstack with OpenStack version "Liberty". I can create instances on the machine and SSH into them without any problem. The devstack is created as a single node with the controller and the compute being on the same machine. The networking used is Nova with an floating IP range of 172.24.4.0. The problem occurs when I try to ssh to an instance from another computer. I have created a route in the router to direct all traffic from 172.24.4.0 to the IP of the machine where OpenStack is installed. I can telnet into the SSH port from this external machine:I have a strange problem ever since I installed