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44 posts


#147300 15-Jun-2014 17:22
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Slightly complicated set-up, will do my best to explain. All fairly cobbled together.

I am running my own mailserver (using hMailserver), has been up and running for a couple of years, working fine. I have a URL, which keeps the IP address accurate with the MX records etc, no problem with any of this.

I just received an updated modem from Orcon, as I am upgrading from ADSL2+ to VDSL. Set up all the port forwarding to replicate the old modem, and put it in place.

All looks like it's working fine, can RDP in from externally, so the port forwarding is definitely working.

However, INTERNALLY on the LAN, I suddenly can't check the email over IMAP. It announces that it can't connect to the server.

The email clients had been set to my dynamic URL, and had always resolved fine, even when locally. It always used to just identify my router as having the appropriate external IP address, and then port forward from there to the server. However, it seems like with this new router, this isn't working. I've run through all the configuration options I can see, turned off all firewalls etc, but still no luck. Router is a NF4V provided by Orcon, running on their Genius platform.

I had an email client on the same machine as the mail server, which was also connecting to the dynamic URL and failing. When I set it to, it works fine. However, pinging the dynamic URL also works fine, as does the RDP connection, so the issue isn't with the DNS resolution.

Any thoughts of how to make this work? Setting to the local IP address won't work, because I need to take several of these devices outside the LAN.

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  #1066094 15-Jun-2014 17:28
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You need hairpin NAT or NAT loopback, something the vast majority of routers don't support or have enabled by default.

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  #1066098 15-Jun-2014 17:34
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I can enable "Lan Loopback" on each individual NAT entry. Would that be it?


'That VDSL Cat'
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  #1066099 15-Jun-2014 17:34
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markboynz: I can enable "Lan Loopback" on each individual NAT entry. Would that be it?

sounds about right, no harm in trying regardless!

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Any comments made are personal opinion and do not reflect directly on the position my current or past employers may have.


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  #1066103 15-Jun-2014 17:45
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Seems to have worked, thanks! I still seem to have some issues, but not the ones I was having, so back to the troubleshooting drawing board!

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Master Geek

  #1066139 15-Jun-2014 18:54
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or split DNS, have a static A record entry for the DYNDNS name that points to the Internal IP (eg. 192.168.x.x.) and then when the devices are external to LAN they will pick up the external IP.

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