Скачать или смотреть ACL | Configure Access Control List | CCNA 200-301| Network Zeal

Configuring an *Access Control List (ACL)* involves defining rules that specify *which users or devices* can access certain resources on a *network or system**. ACLs are commonly used in **routers, firewalls, and operating systems* to enhance security.

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*Steps to Configure an ACL*

*1. Identify the Type of ACL*
There are two main types of ACLs:
*Standard ACL* – Controls access based only on **source IP address**.
*Extended ACL* – Controls access based on *source & destination IP, protocol, port numbers, etc.*

*2. Choose the Placement of ACL*
**Inbound ACL**: Filters traffic **before it reaches the destination**.
**Outbound ACL**: Filters traffic **before it leaves the interface**.

*3. Define ACL Rules*
Each ACL consists of a **list of permit or deny rules**. The order of rules is crucial because ACLs are processed **top to bottom**.

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*Configuring ACL on Cisco Devices*
Here’s how you configure ACL on *Cisco routers or switches* using the **Command-Line Interface (CLI)**.

*Example 1: Configuring a Standard ACL*
```bash
Router(config)# access-list 10 permit 192.168.1.0 0.0.0.255
Router(config)# access-list 10 deny any
Router(config)# interface GigabitEthernet0/1
Router(config-if)# ip access-group 10 in
Router(config-if)# exit
Router(config)# exit
```
*Explanation:*
`access-list 10 permit 192.168.1.0 0.0.0.255` → Allows traffic from **192.168.1.0/24**.
`access-list 10 deny any` → Blocks all other traffic.
`ip access-group 10 in` → Applies ACL *inbound* on the interface.

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*Example 2: Configuring an Extended ACL*
```bash
Router(config)# access-list 100 permit tcp 192.168.1.0 0.0.0.255 any eq 80
Router(config)# access-list 100 deny ip any any
Router(config)# interface GigabitEthernet0/1
Router(config-if)# ip access-group 100 in
Router(config-if)# exit
Router(config)# exit
```
*Explanation:*
`permit tcp 192.168.1.0 0.0.0.255 any eq 80` → Allows *HTTP (port 80)* traffic from 192.168.1.0/24.
`deny ip any any` → Blocks all other traffic.

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*Best Practices for ACL Configuration*
✅ *Use "deny any any" as the last rule* (implicit deny).
✅ *Be mindful of the order of rules* (processed sequentially).
✅ **Apply ACLs closest to the source for outbound traffic and closest to the destination for inbound traffic**.
✅ *Regularly audit ACL rules* to remove outdated entries.

An *Access Control List (ACL)* is a security mechanism used to define and enforce permissions for users, systems, or processes accessing resources within a network, operating system, or application. It consists of rules that specify which subjects (users or processes) are allowed or denied access to specific objects (files, directories, network resources).

*Types of ACLs*
1. *File System ACLs* – Control access to files and directories in operating systems (e.g., NTFS in Windows, chmod in Linux).
2. *Networking ACLs* – Used in routers, firewalls, and switches to permit or deny network traffic.
3. *Database ACLs* – Define permissions for accessing and modifying data in databases.

*ACL Components*
**Subjects**: Users, groups, or processes requesting access.
**Objects**: Files, directories, network devices, or other resources.
**Permissions**: Read, write, execute, delete, etc.
**Rules**: Define allowed or denied actions for specific subjects.

*Types of Network ACLs*
1. *Standard ACL* – Filters traffic based only on the source IP address.
2. *Extended ACL* – Filters traffic based on multiple parameters like source/destination IP, protocol, and port numbers.

*Example of ACLs*
#### *Linux File System ACL*
```bash
setfacl -m u:username:rwx /path/to/file
```
Grants a specific user read, write, and execute permissions.

#### *Cisco Router ACL*
```cisco
access-list 100 permit tcp any host 192.168.1.10 eq 80
```
Allows TCP traffic to a specific host on port 80.

*Benefits of ACLs*
✔ Granular access control
✔ Improved security and compliance
✔ Protection against unauthorized access