Hi everyone,

I'm posting this after extensive troubleshooting because I'm honestly running out of options and would really appreciate input from the community or TP-Link staff.

 

 

Setup

 

• Model: Deco X50 (3-pack)
• Hardware Version: BR/1.32
• Firmware: 1.3.1 Build 20251122 Rel. 36074
• ISP: Vivo (Brazil)
• ISP Router: Mitrastar GPT-2742GX4X5v6
• Connection Type: PPPoE

 

Topology tested:

 

Scenario A (Working):
ISP Router (routing) + Deco in Access Point mode → ✅ Everything works

 

Scenario B (Problematic):
ISP Router in Bridge mode + Deco in Router mode (PPPoE) → ❌ Problems occur

 

 

Main Issues (ONLY in Router Mode)

 

1) NAT Loopback / Hairpin NAT not working

 

• Minecraft server hosted locally (port 25565 TCP/UDP)
• Port forwarding correctly configured
• External access → ✅ Works
• Internal access via DDNS/public IP → ❌ Fails
• Internal access via local IP → ✅ Works

 

Evidence (PowerShell test):

 

Working (ISP router doing NAT):

 

TcpTestSucceeded : True

 

Failing (Deco doing NAT):

 

TcpTestSucceeded : False
PingSucceeded    : True

 

This strongly indicates NAT loopback is not functioning in Deco router mode.

 

 

2) UDP / NAT Traversal Issues (RustDesk self-hosted)

 

• Ports 21115–21119 TCP/UDP opened correctly
• Server is reachable externally
• Clients fail with:
  “Rendezvous connection failed”

 

This suggests issues with:

 

• UDP handling
• NAT traversal / hole punching

 

Again, this works perfectly when Deco is in AP mode.

 

 

3) General Pattern

 

Everything works perfectly when:

 

• Deco is NOT handling routing (AP mode)
• ISP router handles NAT

 

Problems appear ONLY when:

 

• Deco is responsible for NAT/routing

This includes:

• Port forwarding inconsistencies
• NAT loopback failure
• UDP/NAT traversal issues

 

 

Tests Already Performed

 

• Factory reset and full reconfiguration
• QoS enabled and disabled
• Same behavior across multiple Deco units
• ISP router fully bridged (no double NAT)
• Direct PPPoE on Deco
• Controlled A/B testing between modes

 

Behavior is 100% reproducible.

 

Important Observation

 

This does NOT appear to be a hardware issue.

 

Same devices:

 

• Work perfectly in AP mode
• Fail in Router mode

 

This strongly points to:

➡️ Firmware limitation or bug (NAT / firewall / routing stack)

 

 

Related Community Topics

 

I found multiple similar reports suggesting this is not an isolated case:

 

• NAT loopback issues
• Port forwarding inconsistencies
• Lack of advanced NAT behavior in Deco

 

https://community.tp-link.com/us/home/forum/topic/100811

https://community.tp-link.com/en/home/forum/topic/852690

https://community.tp-link.com/en/home/forum/topic/179984

https://community.tp-link.com/en/home/forum/topic/151141

 

 

Questions for TP-Link / Community

 

1. Is NAT loopback (hairpin NAT) officially supported on Deco X50 in Router mode?
2. Are there known limitations with UDP / NAT traversal (e.g., hole punching)?
3. Is this expected behavior, a known bug, or something that can be fixed?
4. Are there:
   • Beta firmware versions?
   • Hidden/advanced settings?
   • Workarounds?

 

 

Current Workaround

 

I'm currently forced to run:
➡️ Deco in Access Point mode
➡️ ISP router handling NAT

 

This works, but defeats part of the purpose of using Deco as the main router.

 

 

Final Note

 

I also recorded a 40-minute detailed video demonstrating all tests, comparisons, and failures step-by-step. The issue is very well documented and reproducible. The video is in Portuguese, though, so I would have to translate it somehow; that's why I'm writing this detailed post instead.

 

At this point, I just want to understand:

 

➡️ Is this a limitation of the Deco platform?
➡️ Or is this something that can actually be fixed?

 

 

Also, before you tell me to contact my local support, I already have a ticket opened with TP-Link Brazil support, it's just that I've been having an awful experience with support at least up to now, so that's why I'm posting this, since I saw other users also getting support attention in this community and some of them had issues very similar to mine.

 

Any help, confirmation, or insight would be greatly appreciated.

 

Thanks!
Marcel