Object Group in ACL: Best Practices for Network Security
Introduction
ACLs help us to perform various security activities, like packet filtering and network classification. Configuring ACLs is useful when the network is smaller or has a few lines of ACEs. But, it becomes very hard for a device to manage and maintain when we configure so many ACLs on the router. To resolve this problem, Cisco introduced the object group in Cisco IOS version 12.4. The function of the object group is to simplify ACL management. This article will explain object-group in ACL and practical use cases in network security.
What is an object group in ACL?
An object group is a way through which we group multiple objects into a single entity. These objects include IP addresses, protocols, and network services. This object group is then referenced in an ACL, which allows a network administrator to simplify and streamline the ACL.
Rather than writing an ACL for every object, we create a single ACL that will apply to all objects, which want the same access control rules.
For example, if multiple IP addresses need the same type of access control rules, then you can group those IP addresses into a network object group and reference this group in an ACL. It will reduce the number of ACL entries, making the ACL easier to manage and understand.
Types of object-group
Object-group has three types, which are below;
1) Network object-group: It is used to group IP addresses and subnets
2) Service object group: This type of object group is used to group services or port numbers, such as HTTP, HTTPS, FTP, Telnet, etc.
3) Protocol Object-group: When you group different protocols such as TCP, UDP, ICMP, etc, then you will use this type of object-group
The above object group can be combined and referenced in ACLS to create manageable security policies.
Configuration of object-group in Cisco IOS
Configuring an ACL consists of the following steps;
Configuring a Network Object-group
The below example shows you how to create a network object group having the name net-group1. The net-group1 includes three hosts;
Configure service object-group
The next example shows you how to create a service object group having the name service-group1. It consists of ICMP and TCP.
Creating ACL and embed object-group into ACL
When you write respective network and service groups, then the next phase is to create an ACL and embed an object-group in this ACL;
Applying an ACL to the Interface
There are no extra commands to apply an ACL to the interface, but it’s normal as we do with normal ACLs;
