Double NAT problems?

General Discussions
1

Hi,

I have a slightly unusual set up - but I don’t really think it’s that complicated. I’m having some network related problems though. I actually don’t think this is a double NAT problem, but at the moment I can’t see what else it could be, and I’m not a networking expert so could well be wrong!

I have my ISPs router (BT, in the UK) connected to my telephone line, getting me fibre optic broadband. This has a DMZ set up, which sends everything to my own “Personal” router which is what I use for all my internal networking and wifi.

I then have two plex servers connected to this internal router. One is the Shield TV and one is a PC running Win 7 and the latest version of the plexpass server. At the moment my firewall on Win 7 is turned off.

I have set up port forwarding on the personal router so that public port 32401 forwards to 32400 on my Shield TV and 32402 forwards to 32400 on my PC.

I have set these public ports up on the server “Network” settings page for each server. However, I can’t connect to either of them externally through the following web addresses:

https://MyDynDNS.URL:32401/web
https://MyDynDNS.URL:32402/web

I also cannot connect to them through www.plex.tv

Internally, I can connect to them through the web browser on my PC fine. Under the Network Settings both show:

Not available outside your network
Private Unknown IP <- Public [MY.PUB.LIC.IP]:PORT X Internet

Obviously it’s that X that is the problem but I can’t understand why!

Please help! I’ve had several problems similar to this in the past - I’m fairly sure I must be doing something wrong and I have been reading all the guides and I just can’t figure out what!

Thanks,

James

PS @AsphyxNYC - having read a few threads you know your stuff so I was hoping you may be able to help. (but sorry for calling this to your attention…)

PPS - actually, reading more, it probably is Double NAT - but I’ve implemented the DMZ solution as described in the trouble shooting pages:

◦You can try to set up a port forward in the service provider’s modem/router (in addition to your own). The process is similar, except that you’re using your router’s WAN/Internet/External IP address where you would otherwise enter the local IP address. (See below for information about port forwarding.)

The “external IP address” as my personal router sees it, is not really an external address at all, it’s the address of the BT router. But I’ve forwarded a DMZ from BT router to Personal router, and forwarded ports correctly on the personal router… so I don’t understand why it doesn’t work.

3

I run exactly the same setup you have, but with Verizon Fios. I ran into a similar problem when trying to get Plex to work with Sonos.

The issue I ran into was that requests from the internal LAN to my external IP address were not getting redirected to my personal router. Instead they were going to the ISP router. To test try putting your external IP address into a web browser. Does it bring up the admin page for your ISP router?

If so the fix (for me) was pretty simple. Just add a port forward rule on your ISP router to your personal router for the two ports you are using.

I did not want to put my ISP router into Bridge mode. With Verizon if you do that you lose access to Guide data and VOD.

4

Thank you both.

My ISP router does not have a bridge mode, so I used a DMZ instead, as the next best alternative.

The problem fixed itself when I signed my servers out of Plex and then back in. All the connectivity started working… So far, so good!