Experiencing a mental overload with ACL settings
Experiencing a mental overload with ACL settings
INT refers to a type of access control list entry. It typically specifies the source 192.168.0.0 with full mask, the destination network, and the network interface. You can also set it to block all traffic by using 0.0.0.0 to 0.0.0.0, allowing or denying any incoming or outgoing connections to/from that network. It’s often placed at the end of an ACL for clarity.
INT. The term "interface" simply stands for interface. Let's clarify: if I need to block internet traffic from reaching this int./interface at 192.168.10.2, I might choose either an extended ACL with IP rules or a host-based approach. My question is, should I use the "host" syntax here or another method?
It's been a while since my CCNA course. I think blocking internet traffic should focus on the network you control, not just the interface. Instead of targeting a specific IP range like 192.168.10.0, consider using a more general rule such as "deny ip any 192.168.10.0 0.0.0.255" and then allow all traffic. You'll need to apply this ACL on the internet-facing interface. This approach might prevent incoming connections from that network while still letting other networks reach out. For outbound traffic, you can set up a similar rule at the default gateway, denying all outgoing packets except those destined for internal networks. This way, devices can communicate internally but won't be able to send data to the internet unless explicitly permitted.
Do you have Packet Tracer installed? Please share the file and I'll review it for you.
Another approach I overlooked is adjusting which routing protocol you're using (OSPF, EIGRP, Static, RIP). You can block or disable the route that connects the 10.0 network to the internet. Even then, I’d likely stick with an ACL for finer control and exceptions.
Based on what you shared, it seems the question relates to blocking traffic from a specific router interface rather than configuring a host. You're wondering if a "deny host" setting applies here or how to set up a rule that blocks access to that interface's network. It might help to clarify whether you're trying to restrict the IP address or the physical connection itself. The usual approach would involve defining the network range you want to allow or block, not the interface IP directly.
Packet Tracer typically uses an older style of syntax, whereas NX-OS and IOS-XE have different conventions. On those systems, you'd set up rules like an extended IP ACL to block a host's outbound traffic beyond the interface or restrict ingress/egress from that host. You usually don't deny interfaces directly; instead, you apply the ACL to the interface to control traffic flow at that point.
It really doesn't matter whether it's a real host or just a word—it can still serve its purpose. That's worth keeping in mind. If I'm interpreting your message correctly, my previous comment was directed at the person you mentioned. Filtering outgoing traffic requires setting up an ACL on the internet interface to block traffic heading toward the 10.0 network. For incoming traffic, you'd need to configure an ACL on the same interface to stop traffic coming from the 10.0 network. However, if both ingress and egress are managed on the 10.0 interface, additional CPU resources are being consumed forwarding internet traffic to that network before it's discarded. It seems like a reasonable conclusion, though further details would help.