They are more convenient than numbered access lists because you can specify a meaningful name that is easier to remember and associate with a task. Named ACLs allows standard and extended ACLs to be given names instead of numbers. It allows you to use names to both create and apply either standard or extended access lists. Named access lists are just another way to create standard and extended access lists. This brings us to the concept of a named access list. In such scenarios, standard and extended access lists become unsuitable. In medium to large enterprises, managing access lists can become difficult and complicated over time, especially as the quantity of numbered ACLs grows. By using extended access lists, you can effectively allow users access to a physical LAN and stop them from accessing specific hosts-or even specific services on those hosts. It allows you to specify the source and destination address as well as the protocol and TCP and UDP port numbers that identify them. Extended ACLĮxtended ACLs extend the functionalities of standard ACLs by looking at not just the source but also the destination. This is where Extended ACL comes into play.
The standard ACLs’ inability to look for a destination address renders it ineffective in such scenarios. When you need to decide based on both source and destination addresses, a standard access list won’t allow you to do that since it only decides based on the source address. Standard ACLs do not care about where the packets are going to, rather, they focus on where they’re coming from. It then grants everything from that network either all or no access. The wildcard mask tells the router which parts of an IP address need to match the access list and which do not. Wildcards are used with access lists to specify an individual host, a network, or a certain range By using these numbers, you’re telling the router that you want to create a standard IP access list, so the router will expect syntax specifying only the source IP address. You create a standard IP access list by using the access-list numbers ranging from 1–99 or 1300–1999 (expanded range). They are used to filter network traffic by examining the source IP address in a packet. Standard ACLs are the oldest type of access control lists. There are two main types of access lists: Standard ACL and Extended ACL. When an access list is applied to outbound packets on an interface, those packets are routed to the outbound interface and then processed through the access list before being queued. Any packets that are denied won’t be routed because they’re discarded before the routing process is invoked. When an access list is applied to inbound packets on an interface, those packets are processed through the access list before being routed to the outbound interface. When you create an access list on a router, it’s inactive until you tell that router what to do with it, and which direction of traffic you want the access list applied to-inbound or outbound. Operating systems, applications, firewall, and router configurations are dependent upon access control lists in order to function properly. With the right combination of access lists, security managers gain the power they need to effectively enforce security policies.
For instance, you can configure an access list on a firewall interface to allow only certain hosts to access web-based resources on the Internet while restricting others. Quality of Service (QoS), then whatever traffic matches your access list is going to be prioritized or de-prioritized accordingly.įor the purpose of this article, we’re going to be focusing on the access list applied to interfaces because this is the most common use case for an access list.A route map, then whatever advertisements match your access lists are being accepted by a routing process.A VPN configuration, then whatever traffic you identify with your access list is then encrypted and sent through the VPN tunnel.A network address translation (NAT) configuration, then whatever traffic is identified by the access list is processed through a NAT.An interface, then any traffic that is identified by your access list is permitted through that interface.For example, if you apply your access list to… There are many use cases for access lists. This means that how you apply the access list determines what the access list actually does. It specifies which users or system processes (subjects) are granted access to resources (objects), as well as what operations are allowed on given objects.Īny access attempt by a subject to an object which does not have a matching entry on the ACL configuration will be denied. An Access Control List (ACL) is a tool used to enforce IT security policies.
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