I'm considering switching from BT to Zen Internet when my BT FTTP contract expires in Dec 2025.

My question is: can I do that as shown in the following network diagram?

Home LAN --- (LAN ports) Vigor2866 (Wan2 port) --- (LAN port) Fritz!Box 7530AX (WAN port) --- ONT ---FTTP --- Internet

In words, devices on my home LAN (address range 192.168.1.x) would connect via the WAN2 port on my Draytek 2866 router to a LAN port on a Fritz!Box 7530 AX, and thence via an Openreach ONT over an FTTP link to the internet.

Currently I connect to the internet as shown in the following very similar diagram:

Home LAN --- (LAN ports) Vigor2866 (Wan2 port) --- (LAN port) BT SmartHub2 (WAN port) --- ONT ---FTTP --- Internet

The Draytek 2866 (f/w 4.4.5.9_BT) is configured so its WAN2 port is 'Always on', set to 'Static or Dynamic IP' and 'Obtain an IP address automatically' from 192.168.178.1.

Both the Draytek 2866 and the BT Smart Hub 2 hand-out IP addresses to the devices on their LANs (192.168.1.x and 192.168.178.x).  The BT Smart Hub 2's configuration is as factory settings except for the changed IP address range.

This works fine. And despite the double-NATing (from the SmartHub and the Draytek routers in series), I can make and receive VOIP calls via a Grandstream ATA on my home LAN.

The big advantage (for me) of cascading my 2866 into a BT or Fritz!Box router is that the assignment of IP addresses on my home LAN, and the configured firewall rules applied to the devices on it,  can stay exactly the same if I switch from BT to Zen.

Martin

Unless I'm missing something from your explanation then "he assignment of IP addresses on my home LAN, and the configured firewall rules applied to the devices on it" aren't going to be affected by any change of ISP as these are all internal anyway...to me the ISP router is a complete irrelevance.

Unless I'm missing something from your explanation then "he assignment of IP addresses on my home LAN, and the configured firewall rules applied to the devices on it" aren't going to be affected by any change of ISP as these are all internal anyway...to me the ISP router is a complete irrelevance.

I agree that this point is not relevant to my main question 'Will this cascading of 2866 and the Fritz!Box 7530AX work?' 

Please can anyone who has tried this (or similar) cascade arrangement of Draytek router into Fritz|Box 7530AX comment?

 

Why would it not? - they're just network devices connecting over a LAN in your use case.

My real question is just - 'but why?' You are seemingly introducing complexity for the sake of complexity, it gives you nothing that you couldn't do with just the 2866 on it's own.

My real question is just - 'but why?' You are seemingly introducing complexity for the sake of complexity, it gives you nothing that you couldn't do with just the 2866 on it's own.

My understanding is that to enable digital voice over BT or Zen's systems, I must use the routers they provide. The Vigor 2866 can't pair with a DECT phone or connect with an analogue phone.

That's certaiinly true for BT's Digital Voice.

I've a feeling Zen's system is a bit more "open" but for simplicity I might go for your approach with Zen as well.