In Conntrack SNAT implementation G/w is not reachable when no port in the router subnet is present in the node

In Conntrack SNAT implementation G/w is not reachable when no port in the router subnet is present in the node.

Steps to reproduce
In a 2 node setup
1)Create mulitple routers and associate it with the external n/w.
2)Identify the router which has NAPT switch in the compute node(display-napt-switches).
3)Spawn vm in the controller node and try to reach the external g/w.

Expected Result:

External g/w should be reachable.

Actual Result :

External g/w not reachable.