Zyxel LTE5398-M904 and STUN server

BruCom Posts: 32  Freshman Member
10 Comments Friend Collector
edited January 4 in Mobile Broadband

Hello community

is there any of you that knows if the above modem can use a STUN server ?

I had a look to the user manual and found nothing but I'm not an expert and could this feature goes under another name.

In addition, in the configuration back up file, I saw there are parameters to connect to a STUN server but the WEB interface does not show any. Could it be that such parameters are enabled only when a specific option is selected or are applicable ony to other models other then the LTE5398-M904 ?

Thank you

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  • Friday
    Friday Posts: 64  Ally Member
    First Anniversary 10 Comments Friend Collector First Answer

    Hi @BruCom,

    May I understand your usage of STUN server? Any specific service you would like to achieve?

    thank you!

  • BruCom
    BruCom Posts: 32  Freshman Member
    10 Comments Friend Collector

    Hi @Friday

    STUN server usage was suggested by my VoIP provider to fix disconnections probably due to the fact my 4G provider does not provide a public IP address.

  • tonygibbs16
    tonygibbs16 Posts: 841  Guru Member
    First Anniversary 10 Comments Friend Collector First Answer
    edited April 2023 Answer ✓

    Hi @BruCom

    Session Traversal Utilities for NAT (STUN) is designed so that VoIP will work through firewalls and with private IP addresses and NAT.

    https://www.3cx.com/pbx/what-is-a-stun-server/#:~:text=A%20STUN%20(Session%20Traversal%20of,outside%20of%20the%20local%20network. has some information for example.

    I have used STUN through another Zyxel device in my home set-up in order to get VoIP working, because my phone is on a private IP address inside my local area network.

    If your VoIP provider runs a STUN server, then it will likely work though LTE5398-m904 as long as your 4G provider will also pass it through.

    I downloaded the user guide for LTE5398-M904 from Zyxel's Swiss distributor at https://www.studerus.ch/de/support/downloadcenter/ by searching for it, and it mentions a set-up of an outbound proxy being possible so that you don't have to use STUN or SIP ALG, see below.

    I hope that this helps.

    Kind regards,


  • BruCom
    BruCom Posts: 32  Freshman Member
    10 Comments Friend Collector

    Hi @tonygibbs16

    Thank you very much for your reply.
    I think that my VoIP provider runs a STUN server since, back in March, he provided me the parameters to connect my device to the server together to other suggestions to keep a stable SIP connection.
    Another suggestion from the VoIP provider was to turn on the "keep alive" function.

    I went thru the device manual and did not find a way to connect to a STUN server or a "keep alive" function.
    This is the reason why I opened this tread asking support to the community.

    Anyway, me too I found that page in the user manual and I turned of the SIP ALG, changed the "SIP Register Expiration Duration" to 120 seconds and the "SIP Register Fail Re-try Timer" to 900 seconds.
    This from some time and I must say that the SIP registration is a lot much stable now.
    So, yes, seems that it works though LTE5398-M904 and 4G provider also pass it through.

    Thank you again for you explanation and support.

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