What will happen if ip forwarding is disabled?

When IP forwarding is disabled on a Linux system, it means that the system will not act as a router for packets that are not destined for its own local interfaces. In this context, if a packet arrives that is intended for a remote destination, the system cannot forward that packet to the correct network interface or a gateway.

The understanding here is predicated on how IP forwarding works: when enabled, a system can receive traffic intended for other networks and send it on to its final destination, thus routing packets through the network. Conversely, when it is disabled, this routing capability is turned off. The system can still receive packets, but it will not pass them along to other networks, leading to a situation where no packets will be routed beyond the local device.

In contrast, while packets can still be dropped and local traffic can be processed, the primary effect of disabling IP forwarding specifically prevents the routing of packets, which aligns with the correct answer provided. The system will simply process any packets meant for itself but won't help communicate messages between different networks.