Simple definition
A Linux network namespace isolates interfaces, IP addresses, routing tables, and network sockets.
Purpose and use
A network namespace gives processes a separate view of interfaces, routes and other isolated networking resources.
How does it work?
Virtual interfaces can connect namespaces, but communication requires consistent link and routing configuration.
Example and verification
For a container with no connectivity, inspect interfaces and routes inside its namespace, not only on the host.
Points to watch
Creating the namespace does not automatically establish external access, NAT or a secure filtering policy.
In short
A separate network view needs an explicitly configured communication path.