GWN7000 - Access DDNS from LAN (NAT Loopback?)

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PerfectV

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#230557 1-Mar-2018 13:44

I got a GWN7000 on advice from someone on here. So far, awesome. Gigabit fibre, so far 100 days up time without a blip. The only thing I can't work out is the setting so I can access hit my dynamic DNS address when I'm connected to the LAN. I've got a few apps I used that don't support having 2 server IPs, it's a drag having to change the settings all the time.

Spyware

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#1966503 1-Mar-2018 13:58

http://www.grandstream.com/sites/default/files/Resources/Firewall_Advanced_NAT.pdf

Hairpin NAT consists of a dst-nat and src-nat rule. Google.

PerfectV

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#1966512 1-Mar-2018 14:10

I've gone through that doc a couple times and really can't make much sense of it. Any plain English guidance appreciated

Spyware

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#1966514 1-Mar-2018 14:18

As I inferred you need a dst-nat rule (the port forward from WAN to LAN server device) and a src-nat rule for the reply traffic from LAN server device to the LAN side clients (EDIT: I described it backwards).

Mikrotik example

https://wiki.mikrotik.com/wiki/Hairpin_NAT

Mistenfuru

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#1966523 1-Mar-2018 14:31

LAN Loopback (Hairpin NAT) as above needs a SrcNAT pointed towards your DstNAT rule.

The SrcNat needs to have the Src Group as your internal IP Pool

Basically it picks up anything internally trying to access your WAN IP and points it back towards the required DstNAT instead of dead-ending nowhere.

Sadly I've got an easy guide for this on Mikrotiks but not Grandstreams

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chevrolux

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#1966679 1-Mar-2018 17:38

Your other option would be set a custom DNS entry on your router for your D-DNS domain, and have it resolve to the internal IP address of the server.

cddt

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#3468203 9-Mar-2026 20:50

I requested this post to be unlocked because it comes up on search engines, and I think I can give a good explanation of how to achieve this on Grandstream devices.

I have a GWN7003 which is a bit newer but essentially the same principle.

The goal is to be able to access resources on your LAN which are available with a domain name on the public internet. I.e. you have already configured the appropriate port forwarding, you can access it from outside your network, but you can't browse to www.example.com.

First, I will mention that I tried using "Local DNS" to map my domain name to a local IP. For some inexplicable reason, I could not get this to have any effect.

Next, I set up DNAT with the following configuration.

Name: whatever
Enable: yes
IP Family: IPv4
Protocol Type: TCP (or as you require)
Source Group: select the VLAN of your user devices at home, e.g. your computer, phone, whatever
Source Address Type: IP Subnet
Source Address: add the subnet of the above VLAN
Source Port: I left this blank but you can configure
Destination Group: select the VLAN of the resources you want to access, i.e. where the server is hosted
Destination IP Address: type your WAN address
Rewrite Destination IP Address: type the local address of the resource you want to access
Destination Port: blank or as required
Rewrite Destination Port: blank or as required
NAT Reflection: enabled
NAT Reflection Source: Internal

I hope this helps someone!