DNS and DHCP on Zyxel VMG8825-T50

  • 5 July 2019
  • 8 reacties
  • 11799 Bekeken

Reputatie 1

I've been reading that it is possible to disable DHCP and configure the DNS on the modem Zyxel VMG8825-T50.

However, speaking with support on the telephone and trying this myself, any changes made to these disables the internet. Support on the phone has especifically told me that if I disable DHCP on this modem I will have no internet connection.

My goal is to resolve my own DNS via Raspberry Pi and use Pi-Hole on my home network. Any information about making this work would be appreciated.

Many thanks in advance.

Beste antwoord door yalerta 5 July 2019, 18:28

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8 reacties

Reputatie 1
OK, well thanks for your assistance!
Reputatie 7
Badge +2
About the modem and the quircks I can't give yoy further advice.
The firmware is a Tmobile only and not a general Zyxel.

The only way is the trial and error way. As Tmobile uses the Zyxel just for a couple of months there is not much support about specific settings and there behavior available at the moment.
Reputatie 1
OK, that’s clear, thanks. But do I need to add the secondary DNS for it to work properly? Is this something particular to this modem? In my previous modem I only used one DNS and it was all fine.
Reputatie 7
Badge +2
Normaly spoken, all DNS requests in your network should be sent to the first DNS server, when a time-out occurs the request will be passed to the secondary.
So, as your RaspberryPi is powered on it will handle ALL the DNS requests in your network.
Reputatie 1
But the instructions from Pi-Hole specifically tells not to use a secondary DNS.

"Pi-hole needs to be the only DNS server because it intercepts queries and decides whether or not they should be blocked. If you have other DNS servers configured, you may be sent to the correct domain, bypassing Pi-hole completely."
Reputatie 7
Badge +2
In the first line the fixed IP adres of your RaspberryPi, The second line could be any DNS server like Google's or OpenDNS or even one of the T-mobile servers could be used Primary: Secundary:

Reputatie 1
Thanks for your help. I've followed the guides to the letter and this modem still bypasses the Pi-Hole as a DNS resolver. It is the only and static DNS configured, but Zyxel still uses another DNS somehow.

If I configure my Mac to use my Pi-Hole's DNS, the the Pi-Hole works perfectly well. Any advice?
Reputatie 7
Badge +2
Complete guide

quote from that topic
As stated before, a static IP is needed for Pi Hole to function properly. We already took care of this before. PiHole has DHCP capabilities, which means it can act as your DHCP server and assign IP addresses to your clients. However, most routers can do this well as well. Therefore, we are going to let your router handle that and not use PiHole’s DHCP server. Only a static/fixed IP is needed to proceed further.

The guide shows a simple way to set things up.
If you want the RaspberryPi to handle the DHCP it becomes more complicated and maybe less secure if you are bypassing the Zyxel in terms of a firewall and open ports.

In the Zyxel modem it is possible to set the RaspberryPi IP adres and use it as a DNS server and keep the Zyxel as a DHCP server