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How to connect new 5G Sagemcom Fast 5866T modem to Google Nest wifi?

Level 2
Hey there tech savvy people!
We just got an upgrade to 5G NBN with the brand new Sagemcom Fast 5866T modem. It's up and running but I'm not sure how to connect it to our Google Home nest wifi extender.
Our tv is mounted in our converted garage which is seperated to the rest of the house through a brick wall so we managed to get internet out there to our Sony TV through using a Google nest set up, so we need this to connect to the new modem. Otherwise the tv is useless for streaming.
Please let me know what I can do to connect the my google nest wifi extender or what alternative solutions can be employed to get the wifi to work.

Level 15

Hi @Jaminjam . The Google Nest is configured by phone app, so there's no user guide to read.

The Fast has to run in normal mode; it can't be put into bridge mode.

The Nest might have an operation mode called Access Point. Connect the Nest WAN port to a Fast LAN port.

If the Nest doesn't have that setting, give it another local ip address (eg. and disable DHCP. Connect Nest WAN to Fast LAN. If that doesn't work, connect LAN to LAN.

Level 2

Adding to this reply, a word of caution - Google used have an Access Point mode, but they have changed this to Bridge mode now.  The Google Nest Router (the one you connect with an ethernet wire to the 5G modem/gateway) will be set (in normal operation) to "NAT" mode and the Google Nest WiFi satellites will be in Bridge mode.  In this setup, you will have a Mesh network on the WiFi signal from the Google boxes.  The WiFi network broadcast from the Sagemcom 5G Gateway should be turned off & you shouldn't connect any other ethernet devices to the Sagemcom 5G device.


If you have to connect devices to the Sagemcom 5G device (like a printer) and if your devices (ie a phone)  are using the Google Nest WiFi network, should they need to connect to the printer, then you need the Google Nest Router to be in Bridge mode (  In this case, each Google device will need to be connected to the Sagemcom 5G Gateway's WiFi network and the Mesh functions (seamless handover) will not work.


(I use a different vendor's devices that does support mesh in AP mode & functions as described in @david64 post.) 


The guidance from @david64 about connecting the Google Nest Router to the LAN port on the Sagemcom 5G Gateway is important - regardless of the mode you are using.


This is awesome! Thanks for sharing this, Redjack. 

Level 3
Hi David, can you point me at your guide to setting up a Google Wifi Mesh with a Sagemcom fast 5G router. I can't find it sorry. I am getting the access points go offline every few days and Google are asking me to get my ISP to turn on Bridge mode on the Sagemcom with is not possible of course. I am testing putting the Google Router in the DMZ to see if that makes any difference.
Level 15

Hi @pyrag63 . 

What is the current setting of the Google router?
When you say the access points go offline, how does that show up?
Do wifi devices lose internet access?
How do you fix that?


Google has a lot of help info here:


These are my thoughts which might not be achievable.
Set Google to Access Point mode with DHCP and NAT disabled.
If no Access Point mode, try Dynamic IP (instead of PPPoE) with DHCP and NAT disabled. Sagemcom will allocate a dynamic local address to Google and devices that connect through it. Its ethernet ports can be used. Its wifi can be disabled to use just Google wifi.
Bridge mode might do same thing.

Level 3

Hi @david64 

I have the MK2 set of 3 Google Nest Wifi. The Router is connected to the LAN port of the 5866T. I have dissabled wifi on the 5866T. I have connected the two Google Wifi points to the Google Router via a wifi mesh as there are no LAN ports on these wifi points for an ethernet backhaul. 


The 5866T is configured as default and so is the Google Router so the Google Router is receiving its IP via DHCP from the 5866T. Initially every seems to be working fine with a Great connection status for both Wifi points but after a few days one of the wifi points status says offline and when you talk to it it says a glitch has occured. The interim fix is to reboot the wifi point.


I have searched the internet and spoken to both Google and TPG support about this problem which appears to be a common one. From what i can understand this is probable caused by double NAT. I believe I can only remove one of the NATs by changing either rougter to Bridge Mode. Since you cannot do that on the 5866T the only option is to do so on the Google Router. The problem with that however is that Google Mesh system cannot function in Bridge (AP) mode and i am therefore unable to create a mesh using the Wifi points. From what i read this is not a problem for the TPLink Deco system that can funtion as a mesh in AP mode but you lose some of the advanced fuctionalitry and reporting, which is fine by me.


From what I have read on here there are a few other members who seem to think you know how to overcome this issue, hense my original question to you. 


PS. I have currently added the Google Router to the 5866T DMZ to see if that makes any difference. Some say it may some say not. Nothing ventured noting gained as they say.




Level 15

@pyrag63 . I don't recall being able to offer solutions to Sagemcom problems, just suggestions.

On the Sagemcom, are DHCP and NAT items that can be set independently of each other, or are they both enabled or disabled together.

If they were separate, you could disable DHCP, allocate a fixed IP address to the Google router's MAC address, eg If you wanted to use the other Sagemcom ethernet ports, those devices would need a pre-allocated ip address. NAT is always needed to map between the Sagemcom external ip address and its local devices.

Then, the Google router would have a local ip address for all its devices: the router's LAN port (which could be a switch) and its wifi devices. This could be Its DHCP would allocate addresses 192.168.2.x. Its NAT would map these addresses onto the Google router's ip address on the Sagemcom LAN. The Sagemcom maps its local addresses onto its external address.

Level 3
, I don't see how changing to a fixed IP address will affect double NAT.
Nor do I understand why double NAT is causing my problem in the first place unless there is some weird periodic communication between the wifi points and Google's backend to confirm the mesh is stable that is being affected by it.
What I do read elsewhere is the TPLink does not have this issue with it's Deco system and even if it did at least you can create a mesh in AP mode, unlike Google. Time to return the Google system and buy a TPLink system.
Thanks for trying to help.
Level 2

Here is the correct method (ignore everything above) -

1. Connect your Sagemcom Fast 5866T router as per instructions.

2. Using Google Home app, factory reset your Google Nest router (select Devices -> select the router -> select the Settings wheel -> select Factory reset network at bottom).

3. Connect the Sagemcom Fast 5866T router (select LAN outlet) to the Google Nest router (select WAN port using the LAN connection cable provided.

4. Add the Google Nest router as new device in Google Home app (select Devices -> + Add).

5. You're good to go with two wifi connection points.