Leveraging Junos' Forwarding Classes for Optimal Traffic Handling

In the world of network engineering, traffic handling is a critical aspect that determines the efficiency and reliability of a network. Juniper Networks, a leading provider of networking solutions, offers a robust feature in its Junos operating system known as Forwarding Classes. This feature is particularly useful for those studying for the JNCIS-ENT certification, as it provides a comprehensive understanding of how to optimize traffic handling in a network.

What are Forwarding Classes?

Forwarding Classes (FCs) in Junos are essentially categories of traffic. They are used to classify different types of traffic for Quality of Service (QoS) purposes. By default, Junos provides four forwarding classes: best-effort, assured-forwarding, expedited-forwarding, and network-control. Each of these classes has a different priority level and bandwidth allocation, allowing network engineers to prioritize certain types of traffic over others.

Configuring Forwarding Classes

To configure forwarding classes in Junos, you need to use the class-of-service hierarchy. Here's an example of how to configure a custom forwarding class:

user@router# set class-of-service forwarding-classes class voice queue-num 5

In this example, a new forwarding class named voice is created and assigned a queue number of 5. The queue number determines the priority of the class, with lower numbers having higher priority.

Leveraging Forwarding Classes for Optimal Traffic Handling

Forwarding classes can be leveraged to optimize traffic handling in several ways. Here are a few examples:

  1. Prioritizing Critical Traffic: By assigning critical traffic to a high-priority forwarding class (like expedited-forwarding), you can ensure that this traffic is always given precedence over other types of traffic.

  2. Managing Bandwidth: Forwarding classes can also be used to manage bandwidth allocation. For example, you can assign a large portion of your bandwidth to the best-effort class for general traffic, and reserve a smaller portion for the assured-forwarding class for important but not critical traffic.

  3. Preventing Network Congestion: By properly configuring your forwarding classes, you can prevent network congestion and ensure smooth operation. For instance, you can limit the amount of bandwidth that can be consumed by non-critical traffic, preventing it from overwhelming your network.


Understanding and leveraging Junos' Forwarding Classes is a key skill for any network engineer, especially those studying for the JNCIS-ENT certification. By properly configuring and managing your forwarding classes, you can optimize your network's traffic handling and ensure reliable and efficient operation.

Remember, practice is key when it comes to mastering these concepts. So, don't hesitate to set up a lab environment and experiment with different configurations. Happy studying!

© Ben Jacobson.RSS