Applying ACLs to control traffic flow based on source and destination IP addresses, protocols, and ports involves configuring extended ACLs on routers or layer 3 switches. Extended ACLs provide granular control over traffic filtering by allowing you to specify various criteria in addition to source and destination IP addresses. Here's how you can apply ACLs to control traffic flow based on different parameters:
### 1. Source and Destination IP Addresses:
Extended ACLs allow you to filter traffic based on both source and destination IP addresses. Here's an example of how to apply an ACL to permit or deny traffic between specific source and destination IP addresses:
```plaintext Router(config)# access-list <acl_number> {permit | deny} <protocol> <source_address> <source_wildcard> <destination_address> <destination_wildcard> Router(config)# interface <interface_type> <interface_number> Router(config-if)# ip access-group <acl_number> {in | out} ```
### 2. Protocols:
You can also filter traffic based on specific protocols (e.g., TCP, UDP, ICMP) using extended ACLs. Here's an example of how to permit or deny TCP traffic from a specific source to a specific destination:
```plaintext Router(config)# access-list <acl_number> permit tcp <source_address> <source_wildcard> <destination_address> <destination_wildcard> ```
### 3. Ports:
Extended ACLs allow you to filter traffic based on source and destination port numbers. For example, you can permit or deny traffic to a specific destination port. Here's how you can permit TCP traffic from a specific source to a specific destination port:
```plaintext Router(config)# access-list <acl_number> permit tcp <source_address> <source_wildcard> <destination_address> <destination_wildcard> eq <port_number> ```
### Example:
Let's say you want to permit TCP traffic from the source IP address 192.168.1.0/24 to the destination IP address 10.0.0.1/24 on port 80. You would configure the ACL as follows:
```plaintext Router(config)# access-list 100 permit tcp 192.168.1.0 0.0.0.255 10.0.0.1 0.0.0.255 eq 80 ```
And then apply the ACL to the appropriate interface:
```plaintext Router(config)# interface <interface_type> <interface_number> Router(config-if)# ip access-group 100 in ```
### Additional Considerations:
- Always carefully plan ACL configurations to avoid inadvertently blocking legitimate traffic. - Regularly review and update ACLs to accommodate changes in network requirements. - Use descriptive ACL names and numbers for easier management and troubleshooting. - Verify ACL functionality and test traffic after applying ACLs to ensure they are functioning as intended.