Configuring Traffic Policing on Cisco ASA Post-9.7: A Modern Approach

🚦 Cisco ASA Traffic Policing Post-9.7 – Complete Educational Guide

📚 Table of Contents

• Introduction
• Policing vs Shaping
• Bandwidth Logic Explained
• Why ASA 9.7+ is Better
• Configuration Steps
• CLI Examples
• Verification
• Best Practices
• Key Takeaways
• Related Articles

📖 Introduction

Traffic management is critical in modern networks where multiple applications compete for bandwidth. Without control, high-bandwidth applications can degrade performance for critical services.

💡 Core Idea: Traffic policing enforces strict limits by dropping excess packets instantly.

⚖️ Policing vs Shaping

Traffic Shaping

Shaping delays packets and smooths traffic flow. It buffers data before sending it.

Traffic Policing

Policing enforces a hard limit. Excess traffic is dropped immediately.

🔽 Expand: Real-world analogy

Shaping = traffic signal controlling flow Policing = strict gate that blocks extra vehicles

📊 Bandwidth Logic Explained

Example policing rule:

police output 1000000

This means 1,000,000 bits per second (1 Mbps).

If incoming rate exceeds this:

• Conforming packets → allowed
• Exceeding packets → dropped

💡 Important: Policing does not queue packets — it drops them instantly.

🚀 Why ASA 9.7+ is Better

• Granular class-based control
• Hierarchical policing
• QoS integration

🔽 Expand: What is Hierarchical Policing?

It allows nested policies. You can control traffic globally and within specific classes simultaneously.

⚙️ Configuration Steps

Step 1: Create Access List

access-list HTTP_TRAFFIC_ACL extended permit tcp any any eq 80

Step 2: Create Class Map

class-map HTTP_TRAFFIC_CLASS
 match access-list HTTP_TRAFFIC_ACL

Step 3: Create Policy Map

policy-map POLICE_HTTP_POLICY
 class HTTP_TRAFFIC_CLASS
  police output 1000000 conform-action transmit exceed-action drop

Step 4: Apply Policy

service-policy POLICE_HTTP_POLICY interface outside

💻 CLI Output Example

ASA# show service-policy interface outside

Class-map: HTTP_TRAFFIC_CLASS
  Packets transmitted: 102345
  Packets dropped: 2345
  Current rate: 950000 bps

🔽 Expand CLI Explanation

This output shows how much traffic passed and how much was dropped due to policing.

🔍 Verification Commands

show service-policy interface outside

🧠 Best Practices

• Use policing carefully with UDP traffic
• Avoid aggressive limits on VoIP/video
• Monitor regularly
• Apply hierarchical policies for large networks

🔽 Expand: TCP vs UDP behavior

TCP adapts to packet loss. UDP does not — leading to potential quality issues.

🎯 Key Takeaways

• Policing enforces strict bandwidth limits
• ASA 9.7 introduces better control
• Hierarchical QoS improves flexibility
• Monitoring is essential

📘 Final Thoughts

Traffic policing is a powerful tool when used correctly. With ASA 9.7+, network administrators gain precise control over bandwidth, enabling better performance and fairness across applications.