My IPGateway is NSG4000 (made in Taiwan), in its static routing table I want to assign IP 0.0.0.0 and Subnet mask 0.0.0.0. But I don't know why it can't assign that IP and SM :confused: .
Are there any other way to assign IP and SM 0.0.0.0? Please help me!
Thanks!

Not familiar with that brand, but some routers, often older ones don't like
All zero's as a subnet mask. Maybe try 255.255.255.255

Also a route of 0.0.0.0 may be viewed by your router as the equivalent to the "Default Gateway". If you configured a default gateway, maybe the router won't allow all zeros as a static route. Try removing the default gateway address and then re-entering the all zeros static route.
Maybe your router doesn't allow you to have both configured.

Also confirm that you can ping the "next hop" address you are assigning.
If the "next hop" address is not a valid address or reachable, some routers
Won't display the static route at all in the routing table, and considers it invalid.