Best Practices for Preventing Network Loops with Omada SDN Solutions

Network loops are a phenomenon that occur when there are multiple paths between two devices in a network, resulting in an infinite loop of data transmission. This loop leads to broadcast storms, MAC table instability, and a significant degradation in overall network performance, and in some cases, even a complete network crash.

There are several techniques and precautions that can be taken to both prevent and resolve Ethernet network loops. These techniques and precautions include using Spanning Tree Protocol (STP), Loopback Detection, Ethernet Ring Protection Switching (ERPS), etc.

Omada SDN Solutions incorporate two key mechanisms: STP and Loopback Detection. Loopback detection is a feature that identifies loops in the network. When a loop is detected, the system can automatically block certain ports to break the loop and maintain network stability.

STP is a network protocol designed to prevent network loops in Ethernet networks. STP creates a spanning tree within a network of connected layer-2 bridges (typically Ethernet switches), and disables all other links that are not part of the spanning tree, thereby preventing loops.

Using Loopback Detection alone may cause the upper switch(es) to incorrectly block the port, which has an expanded impact on the network. While only using STP may lead to frequent spanning tree convergence due to link state changes of edge port devices, such as an AP, Camera ports, which will cause network instability.

Therefore, by combining these two features, network loops can be effectively avoided and resolved at all levels of the network topology, and the impact of topology changes on the network can be minimized.

Omada SDN Solution recommends configuring the STP feature on the trunk switch ports between switches, and the Loopback Detection feature on the access switch ports connected wired clients like wireless APs and IP cameras. Take the network topology above as an example.

The switch ports used to connect to other switches to make the redundancy network topology are trunk ports.

The switch ports used to connect to Omada EAPs, IP cameras, and other clients are access ports.

For detailed information and instructions on how to configure STP on trunk ports, please refer to Spanning Tree Configuration in Omada SDN Controller mode, where a similar network topology is introduced to establish redundancy and loop-free configuration via STP.

To configure Loopback Detection on access ports, navigate to Site Settings → Wired Networks → LAN → Profile. Then, edit the profile that will be applied to access ports, and select Loopback Detection mode for Loopback Control.

“Loopback Detection Port Based” mode is enabled for the “All” profile. Other profiles generated by the controller may have different modes depending on the controller version. It is recommended that you check and change the Loopback Control mode to “Port Based” if a profile is applied to access ports.

After enabling loopback detection on the port profile, the feature is automatically enabled on the access ports that are bound to the profile.

• Loopback Detection Port Based: When a loop is detected on a port, the port will be blocked, which is commonly used.
• Loopback Detection VLAN Based: When a loop is detected on a VLAN, the VLAN will be blocked.
• Spanning Tree: STP will be enabled on the port. Choose this mode for trunk ports.

You can also enable the feature using port profile override:

1. Go to Devices, click a switch, then click “Ports”.
2. Edit a switch port, or batch edit some switch ports.
3. Check “Profile Overrides”
4. Select “Loopback Detection Port Based”
5. Click “Apply” to ensure the feature takes effect on the designated ports.