Resolve Spanning Tree Protocol Network Loop on UniFi Switch

draft · network spanning-tree-protocolnetwork-loopunifi

Generated by docuprocessor (prompt article/v3) · 2026-04-22 09:59

Source thread

thread_id: spaces/AAAA05BdS6s/threads/SK1phbxpYZw · 6 msgs · first 2024-08-13 · participants: Tech ATech BTech C

Tech A 2024-08-13 14:42

Hey guys, is anyone familiar with Soul Dental - Amsterdam office? I'm trying to reboot their AP's, but I don't have any admin pwd, or information related... I tried to log in to 192.168.1.1 to see what they have there on that office. Even our dht user was not at bitrix, I just added it

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**Screen Contents – Remote Session via LogMeIn to SDA-SERVER** A UniFi OS login page is open at **192.168.1.1** (marked "Not secure / Error") with credentials **admin/\*\*\*\*\*\*\*\*\*\*** entered. SoftPerfect Network Scanner shows a completed scan of range **192.168.30.1–255**, returning **28 computers**, with notable hosts including: **192.168.30.55 SDA-INSVER**, **192.168.30.56 SDA-CBCT**, **192.168.30.100 SDA-SERVER**, **192.168.30.111 SDA-WIN-Recp2**, **192.168.30.88 SonosZP**, and **192.168.30.89 HPBDDF25**. The LogMeIn session info panel (lower right) shows: **Host: SDA-SERVER**, **OS: Windows 10.0.20348 64-bit**, **Service Tag: 4RGRMH3**, **Uptime: 0 days 1 hrs 6 mins**, **Memory: 20.8GiB / 255.6GiB (8% used)**.

Tech B 2024-08-13 14:42

@Albert Khaydatov

Tech C 2024-08-13 14:43

we have our unifi.ui.com account that it's under. support@dentalht.com 1q2w3e!Q@W#E I have MFA, you can add it to bitrix.

Tech A 2024-08-13 14:44

Added, thanks!

Tech A 2024-08-13 15:04

Well. I restarted the AP's.. Some sonos are working, but I found that I have 3 Sonos One connected by Ethernet, and I'm having this issue at this switch

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**UniFi Network Controller – Port Management View (192.168.1.1)** Port 1 displays a **Spanning Tree Protocol (STP) warning**: *"Blocked by Spanning Tree Protocol to prevent a network loop. This port will be automatically re-enabled when the loop is no longer detected."* Port 1 is configured as **Active**, Native VLAN **MainNet (2) / 192.168.30.0/24**, Tagged VLAN Management set to **Block All**, PoE **Off**. Additionally, **Port 8** and **Port 23** show **Warning (triangle) indicators** in the port diagram, with connected devices labeled **SonosZP** (Port 8) and **Sonos...** (Ports 1 and 23); ports 22–24 are also highlighted with warning indicators.

Tech C 2024-08-13 15:08

their whole network was down this morning, after Alexandra restarted network devices most stuff came back online. Now since you see a network loop, can they look into that and see whats causing it exactly?

---
title: "Resolve Spanning Tree Protocol Network Loop on UniFi Switch"
category: network
tags: ["spanning-tree-protocol", "network-loop", "unifi"]
source_thread_id: "spaces/AAAA05BdS6s/threads/SK1phbxpYZw"
source_space: "spaces/AAAA05BdS6s"
generated_at: "2026-04-22T09:59:14"
participants: ["Tech A", "Tech B", "Tech C"]
---

# Resolve Spanning Tree Protocol Network Loop on UniFi Switch

## Problem

A UniFi switch at a client office was experiencing Spanning Tree Protocol (STP) blocking on multiple ports due to a detected network loop. Port 1 displayed the warning "Blocked by Spanning Tree Protocol to prevent a network loop. This port will be automatically re-enabled when the loop is no longer detected." Additional warning indicators appeared on ports 8, 22, 23, and 24, with Sonos devices connected to ports 1, 8, and 23. The entire network had been down earlier in the morning, and while most devices came back online after restarting network equipment, the STP loop issue persisted.

## Resolution

1. Access the UniFi Network Controller at 192.168.1.1 using admin credentials
2. Navigate to the port management view to identify which ports are showing STP warnings
3. Examine the physical network topology to identify potential loop sources:
   - Check for multiple ethernet connections between the same devices
   - Verify that Sonos devices are not creating bridge connections between network segments
   - Look for accidental cable connections that create redundant paths
4. Temporarily disconnect ethernet cables from devices showing STP warnings (in this case, Sonos devices on ports 1, 8, and 23)
5. Monitor the UniFi controller to confirm STP warnings clear
6. Reconnect devices one at a time to isolate which connection is causing the loop
7. Reconfigure or relocate the problematic connection to eliminate the redundant network path

The root cause investigation was still in progress when the thread ended.

## References
- Source discussion: `spaces/AAAA05BdS6s/threads/SK1phbxpYZw`
- Attachments:
  - ![image.png](../attachments/SK1phbxpYZw.SK1phbxpYZw/image.png) — **Screen Contents – Remote Session via LogMeIn to SDA-SERVER**

A UniFi OS login page is open at **192.168.1.1** (marked "Not secure / Error") with credentials **admin/\*\*\*\*\*\*\*\*\*\*** entered. SoftPerfect Network Scanner shows a completed scan of range **192.168.30.1–255**, returning **28 computers**, with notable hosts including: **192.168.30.55 SDA-INSVER**, **192.168.30.56 SDA-CBCT**, **192.168.30.100 SDA-SERVER**, **192.168.30.111 SDA-WIN-Recp2**, **192.168.30.88 SonosZP**, and **192.168.30.89 HPBDDF25**. The LogMeIn session info panel (lower right) shows: **Host: SDA-SERVER**, **OS: Windows 10.0.20348 64-bit**, **Service Tag: 4RGRMH3**, **Uptime: 0 days 1 hrs 6 mins**, **Memory: 20.8GiB / 255.6GiB (8% used)**.
  - ![image.png](../attachments/SK1phbxpYZw.s5xYP08Bm7o/image.png) — **UniFi Network Controller – Port Management View (192.168.1.1)**

Port 1 displays a **Spanning Tree Protocol (STP) warning**: *"Blocked by Spanning Tree Protocol to prevent a network loop. This port will be automatically re-enabled when the loop is no longer detected."* Port 1 is configured as **Active**, Native VLAN **MainNet (2) / 192.168.30.0/24**, Tagged VLAN Management set to **Block All**, PoE **Off**. Additionally, **Port 8** and **Port 23** show **Warning (triangle) indicators** in the port diagram, with connected devices labeled **SonosZP** (Port 8) and **Sonos...** (Ports 1 and 23); ports 22–24 are also highlighted with warning indicators.

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