Gotcha. It’s possible your modem was trying to act as a router as well, which would cause a Double-NAT situation. Most ISPs will ship a modem/router combo, but the router part is always fucking dog water. And the issue with double-router setups is that if you try port forwarding on your router, the ISP’s router won’t automatically detect the open port, so you’ll still be blocked.
If you do end up looking into it again, see if the modem allows you to set up bridge mode or DMZ mode, and point it to your router. (You’ll need to undo any old port forwarding stuff you attempted last time first, or else it won’t work!) Basically, this takes all of the modem traffic and passes it directly to your personal router, instead of trying to do routing on the modem/router. Which is honestly what you want, because your personal router is almost certainly going to be better than the shitty one they ship. This will eliminate the Double-NAT situation, because the ISP’s router is going to be completely disabled and is passing all of the traffic directly to your router.
It’s also possible that CenturyLink runs CG-NAT, which would cause a Double-NAT situation on the ISP’s side. More and more ISPs are running CG-NAT to avoid transitioning to IPv6 as long as possible. Basically, there aren’t enough IPv4 addresses available anymore, so ISPs have started giving the same IPv4 address to multiple users using CG-NAT. Your public IP will be shared with multiple users via CG-NAT, the same way your router is sharing the internet connection with multiple devices via NAT. You can check your public IP address in your modem (or your router, if you set up DMZ earlier.) If you’re within the 100.64.x.x to 100.127.x.x range, CenturyLink probably has you on CG-NAT (since those are the public addresses reserved for CG-NAT.) But this breaks port forwarding, because you would also need to forward the port at the carrier level, (which you have no way of doing.)
If they do have you behind CG-NAT, your only real option is going to be a reverse proxy. Basically, Plex/Jellyfin would ping a remote server, which then proxies the request down to your server. It wouldn’t require any port forwarding on the server’s side, because the proxy will be using https directly. Nginx is a popular free reverse proxy service.
Edit: Please see my other comment here as well, regarding securing your router.
Once I figured out what my modem thought my router’s address even was that worked immediately. Jellyfin is still giving me one minor headache after another but it is working, and these are all issues I can solve.
Now I have the unenviable task of resuming work on ripping literally hundreds of DVDs.
Sorry for the double reply. Just had a thought and wanted to make sure you saw it. If you have set your modem to bridge mode, make sure your personal router has a good password, and isn’t just using the default credentials. Since the modem is passing all the traffic straight to your personal router, your router is basically acting as your network firewall… Which means it is handling all of the security; Keep the firmware updated, (depending on the brand, it probably has an auto-update option!) and change the default login credentials.
Also, since you know how to port forward things, consider turning UPnP off. It’s a security risk, (it allows virtually any device on your network to request open ports, which means malware and insecure IoT devices can request open ports too,) but many routers ship with it enabled by default because they don’t want to deal with people calling in to complain about their washing machine being unable to connect to the internet.
I figure you probably already did… But I’d be negligent if I didn’t at least mention it.
Gotcha. It’s possible your modem was trying to act as a router as well, which would cause a Double-NAT situation. Most ISPs will ship a modem/router combo, but the router part is always fucking dog water. And the issue with double-router setups is that if you try port forwarding on your router, the ISP’s router won’t automatically detect the open port, so you’ll still be blocked.
If you do end up looking into it again, see if the modem allows you to set up bridge mode or DMZ mode, and point it to your router. (You’ll need to undo any old port forwarding stuff you attempted last time first, or else it won’t work!) Basically, this takes all of the modem traffic and passes it directly to your personal router, instead of trying to do routing on the modem/router. Which is honestly what you want, because your personal router is almost certainly going to be better than the shitty one they ship. This will eliminate the Double-NAT situation, because the ISP’s router is going to be completely disabled and is passing all of the traffic directly to your router.
It’s also possible that CenturyLink runs CG-NAT, which would cause a Double-NAT situation on the ISP’s side. More and more ISPs are running CG-NAT to avoid transitioning to IPv6 as long as possible. Basically, there aren’t enough IPv4 addresses available anymore, so ISPs have started giving the same IPv4 address to multiple users using CG-NAT. Your public IP will be shared with multiple users via CG-NAT, the same way your router is sharing the internet connection with multiple devices via NAT. You can check your public IP address in your modem (or your router, if you set up DMZ earlier.) If you’re within the 100.64.x.x to 100.127.x.x range, CenturyLink probably has you on CG-NAT (since those are the public addresses reserved for CG-NAT.) But this breaks port forwarding, because you would also need to forward the port at the carrier level, (which you have no way of doing.)
If they do have you behind CG-NAT, your only real option is going to be a reverse proxy. Basically, Plex/Jellyfin would ping a remote server, which then proxies the request down to your server. It wouldn’t require any port forwarding on the server’s side, because the proxy will be using https directly. Nginx is a popular free reverse proxy service.
Edit: Please see my other comment here as well, regarding securing your router.
OH MY GOD
Edit, to add:
Once I figured out what my modem thought my router’s address even was that worked immediately. Jellyfin is still giving me one minor headache after another but it is working, and these are all issues I can solve.
Now I have the unenviable task of resuming work on ripping literally hundreds of DVDs.
Sorry for the double reply. Just had a thought and wanted to make sure you saw it. If you have set your modem to bridge mode, make sure your personal router has a good password, and isn’t just using the default credentials. Since the modem is passing all the traffic straight to your personal router, your router is basically acting as your network firewall… Which means it is handling all of the security; Keep the firmware updated, (depending on the brand, it probably has an auto-update option!) and change the default login credentials.
Also, since you know how to port forward things, consider turning UPnP off. It’s a security risk, (it allows virtually any device on your network to request open ports, which means malware and insecure IoT devices can request open ports too,) but many routers ship with it enabled by default because they don’t want to deal with people calling in to complain about their washing machine being unable to connect to the internet.
I figure you probably already did… But I’d be negligent if I didn’t at least mention it.
Hah, glad I could help. I had a very similar issue, so I understood the frustration completely.
Edit: Please see my other comment here as well.