What is the impact of the firewall ruleset that rejects ICMP packets?

The impact of a firewall ruleset that rejects ICMP packets primarily affects the ability of remote networks to send and receive ICMP traffic, which includes the widely used "ping" command. When the firewall is configured to reject these packets, it restricts the ability of external entities to check the availability or reachability of devices within the protected network.

This becomes particularly important for troubleshooting and network diagnostics, as tools that rely on ICMP, such as ping, will not work if the packets are blocked. As a result, remote networks trying to diagnose issues or determine the status of devices on the internal network would be unable to do so, leading to difficulties in network management.

In contrast, rejecting ICMP packets does not inherently affect SSH access from remote networks to internal resources, nor does it prevent internal hosts from communicating with each other using ICMP for pinging. Stateful multi-layer inspection being enabled signifies a more complex security approach rather than a direct impact of blocking ICMP traffic. Thus, the most fitting conclusion regarding the impact of rejecting ICMP packets is that remote networks cannot ping for troubleshooting purposes.