What effect would the Router1(config-ext-nacl)# permit tcp 172.16.4.0 0.0.0.255 any eq www command have when implemented inbound on the f0/0 interface?

The command Router1(config-ext-nacl)# permit tcp 172.16.4.0 0.0.0.255 any eq www when implemented inbound on the f0/0 interface would have the effect of:

“Traffic originating from 172.16.4.0/24 is permitted to all TCP port 80 destinations.”

This command configures an extended access control list (ACL) on a router. Here’s the breakdown of the command:

• permit tcp: This specifies that the rule allows TCP traffic.
• 172.16.4.0 0.0.0.255: This is the source IP address range. 172.16.4.0 with the subnet mask 0.0.0.255 represents all IP addresses from 172.16.4.0 to 172.16.4.255, which is the 172.16.4.0/24 subnet.
• any: This means the rule applies to traffic going to any destination IP address.
• eq www: This specifies that the rule applies to traffic destined for the standard HTTP port, which is port 80 (denoted by www).

So, the command effectively allows all TCP traffic originating from the 172.16.4.0/24 subnet and destined for port 80 (HTTP) on any host. Other types of traffic from this subnet, or TCP traffic to ports other than 80, would not be permitted by this rule. It’s important to remember that this rule is part of an access control list, and the effect of the ACL depends on the other rules in the list and the order in which they are placed.