I am having issues with NAT Loopback not working with my RBR750 when accessing a resource on my local LAN.I've reviewed this thread (Orbi NAT Hairpinning/Loopback Not Working - NETGEAR Communities) but it did not provide an answer to my issue. I running a Synology NAS with DDNS and Quick-Connect Configured. Port forwarding has been configured and appears to be working correctly to access the Management Console on port 5001, when outside my local network. However, if attempt to connect by the FQDN or Synology Quick-Connect address inside the LAN network it is not reachable. My configuration:Xfinity Modem in Bridge ModeRBR750 setup in Routing ModeWAN port of Router is the ISP issued public IP address which does match and resolve to the DDNS entryGateway is a public Xfinity addressDNS Server Configuration:75.75.75.7575.75.76.76Firmware version: 4.6.14.3As noted port forwarding appears to be working correctly as the resource is available outside my local network. While on the local network I am able to access the resource using the local private IP address, but via the host name assigned in DDNS or by the Synology Quick-Connect ID. Any thoughts or suggestions on resolving the resolution and routing of this resource?

(sigh) This is so tedious. Posts are deleted before I get around to answering them. I manually installed firmware v4.6.14.3 on the RBR750 and performed the NAT-loopback experiment again: Ports 5000 and 5001 forwarded to a computer on the RBR750 LAN at 10.0.0.2 Start Rebex web server on the computer, listening to ports 5000 and 5001 Connect Chromebook to the RBR750 WiFi Open Chrome web browser to the WAN IP of the RBR750 (192.168.1.71 with ports 5000 and 5001).Both ports forward to the web server as they did on the most recent firmware. On a computer on the primary network, open a web server to 192.168.1.71. Both ports 5000 and 5001 connect to the web server on the computer attached to the RBR750. Only about 20 minutes wasted. Not as much time as I spent messing up today's Sudoku in the newspaper. My conclusion: NAT hair-pinning (loopback) behaves exactly the same way on the RBR750 using firmware v4.6.14.2 as it does using firmware v7.2.6.31 I remain convinced the issue is related to whatever Synology is doing when it connects on port 5001.

Do you have any RBS? If so, what model RBS do you have? Has this worked for you at all in this configuration? Or is this the first time setting this up? Have you tried the ISP modem in router mode and the RBR in AP mode to see if loopback works at the modem?

I do have two RBS750 satellites on the mesh. I have not attempted to set up the modem in routing mode as it is an Xfinity provided router and to my knowledge and research understand Xfinity blocks local NAT loopback if serving as the router.

Ok, was wondering about the RBS as your still on older FW and newer v7 FW doesn't work with RBS350 series. The RBS750 series is good with v7 FW. Could try updating to v.21 FW and see if this changes anything. Wondering if the ISP could block any router for NAT loopback...not sure here.

Thank you. I will try to update the FW tonight and report back. That would be interesting if ISP would be able to block. From my experience with routing, the RBR should have identified the resolved IP address as itself and not even forwarded to the modem. The other thing to note is that I've configured DHCP for local clients to use the RBRs LAN address as the DNS server. I may try to override and use Google or Xfinity DNS addresses just to see if it is a local name resolution issue.

RBR750 Local NAT Loopback Not Working

25 Replies

FURRYe38
Guru
Jul 09, 2024
Do you have any RBS? If so, what model RBS do you have?

Has this worked for you at all in this configuration? Or is this the first time setting this up?

Have you tried the ISP modem in router mode and the RBR in AP mode to see if loopback works at the modem?
- kbrumbaugh
  Aspirant
  Jul 09, 2024
  I do have two RBS750 satellites on the mesh. I have not attempted to set up the modem in routing mode as it is an Xfinity provided router and to my knowledge and research understand Xfinity blocks local NAT loopback if serving as the router.
  - FURRYe38
    Guru
    Jul 09, 2024
    Ok, was wondering about the RBS as your still on older FW and newer v7 FW doesn't work with RBS350 series. The RBS750 series is good with v7 FW. Could try updating to v.21 FW and see if this changes anything.
    
    Wondering if the ISP could block any router for NAT loopback...not sure here.
- CrimpOn
  Guru
  Jul 09, 2024
  Totally "my bad" about the 350.
  
  Is DDNS set up
  
  On the Synology, or
  
  On the Orbi router?
  
  I find the documentation about Synology Quick Connect confusing. Specifically, the comment that Quick Connect "works better" if ports 5000, 5001, and 6690 are forwarded through the customer router.
  
  https://kb.synology.com/en-global/DSM/help/DSM/AdminCenter/connection_quickconnect?version=7
  
  What the heck? Does Quick Connect function through port forwarding or is it like so many Internet of Things connections (using an IP connection established by the Synology connecting to a Cloud service)?
  - kbrumbaugh
    Aspirant
    Jul 09, 2024
    DDNS is configured on the Synology.
    
    Quickconnect appears to punch a whole like other IOT devices. Because Synology serves as a proxy for this service, I typically keep it turned off for security. However, I've enabled it to try to assist with troubleshooting this more general DDNS resolution and routing issue.
    
    Synology_QuickConnect_White_Paper_enu.pdf
CrimpOn
Guru
Jul 09, 2024
The question about specific model of satellites was because Netgear created a "cheaper package" that included one RBR750 router and two RBS350 satellites. While the RBR750 now has updated firmware, the RBS350 firmware has not been updated and updating the router will make it incompatible with the satellites. Users who purchased that package have been through very unpleasant efforts to get their systems working again.
- FURRYe38
  Guru
  Jul 09, 2024
  Glad this user doesn't have to worry about that here.

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RBR750 Local NAT Loopback Not Working