What is the valid number range for standard ACLs on Cisco devices?
Correct Answer: A
Detailed Explanation: Access Control Lists (ACLs) are essential tools used by network administrators to filter traffic and control access to network resources. Cisco devices support different types of ACLs, including standard and extended ACLs. The valid number range for standard ACLs on Cisco devices is 1-99. Understanding this range is crucial for proper ACL configuration and troubleshooting. Standard ACLs are designed to filter traffic based solely on the source IP address. Because they offer less granular control compared to extended ACLs, they are assigned a more limited range of numbers, specifically 1 through 99. When a network administrator configures a standard ACL, they are able to specify which source addresses are permitted or denied access. For example, a command such as: access-list 10 permit 192.168.1.0 0.0.0.255 would allow traffic from the entire 192.168.1.0/24 network, provided that the ACL number (in this case, 10) falls within the 1-99 range. Extended ACLs, on the other hand, provide more detailed filtering capabilities, including the ability to filter based on both source and destination IP addresses, protocol type, and port numbers. These ACLs use a different number range, typically 100-199. The division between standard and extended ACL number ranges ensures that configurations do not conflict and that network administrators can quickly identify the type of ACL based on its assigned number. The use of ACLs in network security is fundamental. They are applied to router interfaces—either on inbound or outbound traffic—to restrict or allow packets based on the defined criteria. Standard ACLs, with their limited range and filtering capabilities, are often used in simpler scenarios where only the source address is of concern. For example, they might be used to restrict access to a particular segment of the network from a specific IP address range. Choosing the correct ACL type and number range is an important part of network design and security policy implementation. The use of the 1-99 range for standard ACLs is a legacy from earlier Cisco IOS versions but remains in use today. This consistency allows for easier understanding and maintenance of ACL configurations across various Cisco devices and software versions. For those studying for the CCNA exam, it is vital to remember the difference between standard and extended ACL number ranges. Knowing that standard ACLs are numbered 1-99, while extended ACLs typically fall within 100-199, will help you correctly configure and troubleshoot ACLs on Cisco devices. This fundamental piece of knowledge is often tested, as it underpins more advanced topics in network security and traffic management. In summary, the valid number range for standard ACLs on Cisco devices is 1-99. This range reflects the limited scope of standard ACLs, which filter traffic based only on source IP addresses, and distinguishes them from extended ACLs that offer more granular control using a different number range.
This CCNA practice question helps students prepare for Cisco networking certification exams by testing knowledge of network fundamentals, routing, switching, and network security concepts.