C3000Z port forwarding does not work

nickmo Posts: 3  Freshman Member
edited January 2020 in Smart Home Product
I've recently purchased the C3000Z modem and switched to CenturyLink services.  I have one Windows 10 system which is directly connected into the modem which I need to access using Remote Desktop (port 3389).  As such, I configured:
  1. DHCP reservation for that system (
  2. port forwarding for that system on range 3389=>3389 using TCP+UDP
  3. IPv4 firewall to allow RDP on 3389
However, port forwarding is not working as I cannot RDP into the system from the outside Internet via my public IP.  In using an online port-scan tool, it shows that 3389 is open on my public IP.   

So what's the issue?  Have I missed a modem/router configuration?  Are CenturyLink ISP services blocking it?


All Replies

  • Garrett
    1. Verify that your Windows 10 IP is the same that you want.  " ipconfig /all "
    2. I presume you can access your desktop remotely from your own network, so you have activated the feature in W10. I remember there are rules in Windows Defender for three types of networks, please allow traffic from all of them to 3389 
  • nickmo
    nickmo Posts: 3  Freshman Member
    Yep, IP is the same and I can access it internally both by IP and NetBIOS name.  Ports 3389 were open on the Windows Firewall already, but just for a test, I had already disabled the Windows Firewall altogether.  (Sorry, I didn't mention that previously)

    Are you able to confirm that there is nothing else that should be needed for the port forwarding?
  • nickmo
    nickmo Posts: 3  Freshman Member
    Below is my feedback on this modem, which is equally an indictment against ZyXEL as it is against CenturyLink.  There are major software problems with this modem - if you are an "advanced" technology person who needs more than just out-of-box configurations, then I advise that you RUN AWAY from both ZyXEL and CenturyLink.  In short summary, NEITHER CenturyLink or ZyXEL will support the device.  If you experience an issue and contact CenturyLink, they can only point you to documentation on how to set it up...and NOT on technical issues.  Then CenturyLink will blame ZyXEL and say you need to work with their support.  When you contact ZyXEL, they will blame CenturyLink because they only manufacture the hardware
    and that CenturyLink writes the software for it.  So it becomes a deadlock between the two and you will not be supported.

    Prior to switching to CenturyLink, I did find one review of this device which alluded to one of the problems that I experienced.  In my 1.5 weeks that I used both ZyXEL and CenturyLink, I experienced the following problems.  All these were negatively impacting my ability to
    work from home, so I terminated my services and returned Xfinity (which, by the way, I've had zero problems before and after).
    1. Port forwarding can be enabled and configured, but it doesn't actually work to forward ports. Namely I needed RDP on port 3389, so I don’t know about other ports and if they work.
    2. If you do any VOIP calls, the calls will be dropped mid-stream for anywhere from 5-15 seconds - which occurred during EVERY call that I had, which are multiple calls per day.  Only my work computer was using the network at the time and Internet connectivity speeds showed there were no delays, which to me points to a software and/or service problem. This was ultimately the deal breaker for me, so I did not even attempt to contact CenturyLink for support (given my issues with their support on item #1 above).
    3. There is no Guest network capabilities to segment guest users. Although creating a VLAN should be a workaround to this, enabling the feature (and assigning a network SSID to it) didn't assign the devices to that VLAN.
    If you're a basic user, sure you're probably fine, you just need to accept the risk and the frustrations and the stress.  The one positive experience that I had with CenturyLink customer support was in getting a FULL REFUND.  In providing the above explanation, CenturyLink
    support did not hassle me for a full refund, including installation service fees.

  • Dante
    Dante Posts: 1
    It works if you use application forwarding instead of manually forwarding the ports.
    Advanced Setup > Application Forwarding:
    1. Select your computer name from the drop-down list
    2. Select "Application" from the applications category list
    3. Select "Remote Desktop Connection" from the applications list
    4. Hit "Apply"
    As long as you have a DDNS service (to make sure you are hitting your current home IP if it's not fixed) you will be able to remote in.  I just set it up and I'm remoting into my desktop to provide this answer.
  • EBewley
    EBewley Posts: 1
    I have found that application forwarding does work for some applications and not for others.  For example, I am a software developer, and from time to time I need to test functionality of a mobile app to a web/database server for a few minutes at a time.  Regardless of whether I use the application forwarding for a web server, or I specify the ports specifically, IT DOES NOT WORK.  This point directly to ZYXEL as the culprit.  I've never heard good things about Zyxel, but I can say that without a doubt, it is probably the worst brand of modem to use if you are a developer.  How I use my data service, as long as it is for personal use, should be none of their concern!!!
  • Avindra
    Nothing seems to work. Can the developers look at this issue and fix the firmware? Or else CenturyLink should give us new modems! This is unacceptable service from both the modem vendor and the ISP.

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