How to capture traffic using VACL

Introduction to VACL (VLAN Access Control List)

VLAN Access Control Lists (VACLs) are powerful tools used to capture and filter network traffic on a VLAN. Unlike SPAN (Switched Port Analyzer), which captures traffic on specific ports, VACLs allow for more granular control by applying filters directly to VLANs.

Steps to Capture Traffic Using VACL

1. Create an Access List: Define an access list to specify the traffic you want to capture.
   Copy code

   Cisco_VACL_Capture# conf t
Cisco_VACL_Capture(config)# access-list 150 permit ip any any

2. Create and Apply a VLAN Access Map: Configure the VLAN access map to match the access list and set the action to capture the traffic.
   Copy code

   Cisco_VACL_Capture(config)# vlan access-map VACL_CAP 10
Cisco_VACL_Capture(config-access-map)# match ip address 150
Cisco_VACL_Capture(config-access-map)# action forward capture
Cisco_VACL_Capture(config-access-map)# exit

3. Apply the VLAN Access Map to a VLAN: Bind the access map to the VLAN you want to monitor.
   Copy code

   Cisco_VACL_Capture(config)# vlan filter VACL_CAP vlan-list 100

4. Configure the Capture Port: Define the destination port where the captured traffic will be sent.
   Copy code

   Cisco_VACL_Capture(config)# interface fa0/1
Cisco_VACL_Capture(config)# switchport capture


Benefits of Using VACL for Traffic Capture

• Enhanced Filtering: VACLs provide the ability to filter specific types of traffic within a VLAN, making it easier to isolate and analyze network issues.
• Granular Control: Unlike traditional methods, VACLs offer more precise control over which traffic is captured.
• Efficiency: By capturing only the relevant traffic, VACLs help in reducing the load on monitoring tools and improving analysis accuracy.

Troubleshooting Tips

• Ensure the access list accurately reflects the traffic you need to capture.
• Verify that the VLAN access map is correctly applied to the intended VLAN.
• Check the destination port configuration to ensure it is set up for traffic capture.