FWP with Sky UK router VoIP

Hi all,

I wonder if I can possibly pick the collective Firewalla community brain please.

I'm in the UK and currently run the Sky SR204 modem/router -> FWP (Bridge mode) -> Switch/Mesh etc.

The Sky router is needed only because our landline phone is provided over a proprietary Sky VoIP service - our phone line connects to the back of the router.

I've seen several discussions from users managing to put their own modem/router first, and the Sky router behind it - there are a few tricks required to do this, and I'm wondering if I can achieve this using my FWP as my router, i.e. setting it up as follows:

Modem -> FWP (Router mode) -> Switch -> Mesh etc.
                                                                  -> Sky router

To achieve this, I need to trick my Sky router into thinking it's connected to my ISP.
To do that, I need to:

- give the Sky router an IPv4 address via DHCP with option 43 having "SkyBB-DHCP" as the value ("dhcp-option=43,53:6b:79:42:42:2d:44:48:43:50"). Presumably if I have the Sky router external MAC address, I can configure a dnsmasq option to achieve this?

- delegate a /64 IPv6 prefix from the /56 that sky gives me to the Sky router.

The Sky router needs the IPv4 address before it will move onto the IPv6 connection - the VoIP connection being established over IPv6.

If anyone has any thoughts on whether these are possible on the FWP, and how I might achieve them, I'd be really grateful.

Many thanks in advance,

Dean