port forwarding issue or CGNAT issues.

[ynotchat]

hi, i have been using port forwarding since signing up to talktalk last year and its been working fine, however, recently my port forwards on my router have stopped working. namely port 32400 (plex media server). my server is fine internally, and i can reach it fine from my LAN pc on the same port.

my NAT on my firewall is setup as follows:

port forward snippit

however, my plex server refuses to work externally and any port forwarding checks on websites says my port it closed.

i have UPNP turned off for security and manually forward anything required.

do i have CGNAT enabled? if so, can a talktalk rep disable that on my account please?

or do i have a problem with my router / GFAST dsl modem?

my router is:

TalkTalk Wi-Fi Hub
version SG4K100174

Hardware VersionSoftware VersionGUI Version

hardware version: FAST5364 3.00

software version: SG4K100174

gui version: 5.100.1

and boy old boy, is it a slow GUI for admin on that device.... im not sure that is indicative of the issue, but the admin GUI is not only super slow, but has some bugs where "home" button picutres, do not let you leave a sub menu and you need to logout and back in again to get to other menus... anyway..... thats by the by.

[KeithFrench]

Yes you are right with a CIDR notation 0.0. 0.0/0 defines an IP block containing all possible IP addresses.

However, your rule does not specify the CIDR of 0. Without the CIDR specified, it becomes a bit of a grey area. The IP address 0.0.0.0 allows the computer and servers to temporarily communicate on the network before they receive a valid IP address from a DHCP server.

The default on this router has always been to use * and whilst the CIDR of 0 is correct, it does not follow that the code within the router reacts in the same way to it as *.

Now perhaps in earlier firmware the router did treat 0.0.0.0 like 0.0.0.0/0 as well as *, but maybe it has tightened things down to just *, with V174. However, that is purely a guess on my part, as I have always followed the Sagemcom rule for the External Host field.

[ynotchat]

Keith, thanks very much for the steer, its fixed it instantly.

honestly, no idea what changed on the router side as i was happily running plex last year with the same port forward.

thumbs up from me for the community.

tony.

[ynotchat]

0.0.0.0 was the default if left empty and in networking, also means any host (i.e. 0.0.0.0/0).

it also has worked for the last 6 months unless some update has changed the nomenclature for the source field???

anyway, thanks for the heads up.. i'll edit that source now and see what happens.

[KeithFrench]

I am not surprised your port forwarding does not work. The only device on the internet that you are allowing to access your device is one with the IP address 0.0.0.0, which is invalid. The External Host field needs to be changed to an asterisk (*), which is the default.

The problem of the GUI running slow is a bug that I reported when firmware V174 was released. There is another version due out sometime later this year, hopefully, it will be fixed by then. However, as a customer, I never know what is fixed until it is released.