Final answer:
To fix the issue of local network hosts pinging external networks, you can either create a new Access Control List to block ICMP traffic, remove the 'permit IP any any' from existing ACL (not recommended), apply the ACL to inbound traffic (affects incoming traffic), or block all traffic using the router, which is not typically desired.
Step-by-step explanation:
To address the issue of all hosts on the network being able to ping hosts on networks outside the local segment, we have several options. We could create a new ACL (Access Control List) to specifically block ICMP (Internet Control Message Protocol) traffic from the local segment. This would prevent ping requests from the inside network from reaching external networks. Alternatively, removing the 'permit IP any any' statement from an existing ACL will block all traffic, not just ICMP, so it might not be the desired solution if we want to retain other forms of traffic. Applying the ACL to inbound traffic instead of outbound would affect traffic coming into the segment, not traffic leaving it, which again might not suit our goal here. Lastly, configuring the router to block all traffic from the local segment seems extreme and would isolate the network entirely, which is typically not the desired outcome.