MPoA settings for FTTC Ethernet

I have a customer with a new provision of "FTTC Ethernet" service from Spitfire into one of their offices, i.e. final mile delivery from FTTC infra on copper to the cab, but 'native' backhaul connectivity with no PPP session nailed up over the Openreach infrastructure. I presume it's an Etherflow direct to Spitfire although I am not entirely clear on the method of implementation and routing inside the Openreach network – it also doesn't matter right now.

As I understand it, one of the main benefits of this service is not paying the PPP session efficiency overhead as well as various non-technical service reliability improvements in areas where full Ethernet is not economically or physically viable.

I am really struggling to configure their equipment to pass packets over this service. I'm very comfortable and experienced with all manner of networking, routing, OSPF/BGP etc. I've never worked with an "FTTC Ethernet" line though and the blend of technologies here is eluding me. I just cannot get it to work and I turn to this forum for advice. I'm also lost as to how we can run Ethernet over AAL5 over ATM over ... a sea of protocols and alphabet soup, and indeed why we'd choose to run XoEoA, but architectural questions aside for now. I just need to get this working.

The generic details on the ISP's website are scant and the handover documentation is missing what I perceive to be key information as to encapsulation protocols and similar.

The current tech setup is:

- Draytek Vigor V166 – intending to act as a modem only. Previously a Billion 8800NLv2 but was swapped as it was proving unreliable and slow speeds on native FTTC, also not sure if it supports MPoA. I was hoping the Draytek would be easier to reason about and configure
- Protectli running OPNsense – intending to act as the edge gateway with the WAN IP on its WAN interface and performing NAT for LAN devices

The ISP's handover docs give me the static IP and gateway to use (no subnet mask but I'm assuming it's a /31). They also specify to use "VLAN 4094". That's it. Very scant details on their website too.

I raised a ticket with them and received indication that I need to enable MPoA for this connection. I presume this is RFC 2684 in the Draytek settings. I've configured as follows:

- Physical connections: Draytek has the FTTC line plugged into its DSL port. It goes into sync. It then has an uplink from port 4 I believe into the WAN port of the OPNsense, although I've tried several ports here.
- Draytek configured with RFC 2684 mode enabled in the bridge settings
- Draytek also configured with VLAN 4094 as the native VLAN for the DSL port. I've not specified VLAN 101 as would typically be used by Openreach FTTC, although have experimented with this out of frustration
- WAN interface on OPNsense configured with the provided static IP and gateway.

I've also tried simplifying this arrangement using just the Draytek to also do routing, removing the OPNsense. No luck. Whatever happens, I cannot pass packets over the service, and as there's no PPP session there's no logs I can use to troubleshoot further what might be wrong.

Can anyone with experience provide me a guide on how to get this working, or indeed whether it should work, or whether I have a line fault or similar causing issues upstream? If so, how to debug and check? I feel utterly stupid at this point and may just be missing something obvious. Many thanks.

Edited by scrambledhead (Mon 07-Oct-24 01:12:55)

I know nothing of your specifics, but the beauty of layered protocols is with XoverYoverZ, once you have the oZ working, you need know no more about it while you deal with oY.

So do you have basic connectivity to Spitfire? Do you know where you should connect to for the service you want in TCPIP space? Can you connect to that address? Once you have that, you should not need to know anything about routing or anything within Openreach.

At a pure guess maybe you need to keep VLAN 101 on the VDSL side of things and then tag 4094 on the kit you connect to the LAN port of the DrayTek modem.

My understanding of stuff like this was that it was meant to be a managed service where the ISP denotes their own managed router as the demarc.

This is indeed the problem. The 4094 is meant to be QinQ it seems over VLAN 101 on the FTTC infra according to the ISP. That isn't obvious and perhaps because we're meant to have a router from them as the demarc as you say, essentially their router fulfilling the role that an Adva would fulfil on a typical Ethernet circuit.

I will test these settings at the weekend and hope they cure months of troubleshooting...

Unfortunately not on the connectivity front. It's layered protocols but from the customer side I don't really have any sight of that, as the idea is the router handles all the layering. So seems it either works, or does not. Anyway the problem seems to be that it's VLAN 4094 on QinQ Over VLAN 101 aa per typical FTTC...

I'll need to figure out how to get the modem into bridge mode but maybe that's achieved by adding a VLAN 4094 tag to the WAN interface of the OPNsense so it's also tagging outbound packets.

But at least with this approach I should be able to get something working wholly with the Draytek to confirm it works and then iterate from there.

Thanks for your help.

You jogged my memory and I had a wires-only ethernet (EAD) service once from Spitfire a decade ago which needed a VLAN tag set on the customer firewall WAN port, it the only provider I'd seen at that point who needs this and it's still the only one I've seen since. I only remember it because we had issues because the very new firewall firmware release had issues with VLAN tag values above a certain number.

I've had EoFTTC before (in this case it was a TalkTalk business EoFTTC, although BT Wholesale, Neos and I'm sure others also sell it).

When I had it, a Draytek or Comtrend modem in bridge mode was all that was needed. Obviously still needed VLAN 101 on the DSL port of the modem.

This then just behaved as a really long ethernet cable to the ISP kit at the handover NNI (which was also me). There was a few caveats. The biggest was if you statically configred the IP address on your end, then the Openreach engineers seemed to have no history (but if you used DHCP/PPP it was fine).

The service can also pass VLANs, so if Spitfire are saying there's a VLAN on the client side, then that is technically valid (even if a little unusual).

I can't comment if they've delivered as a /31 or a /30 as I've never used Spitfire but a subnet calculator should help you out there.

Not Spitfire or Draytek, but looking at a legacy FTTC ethernet connection here. the WAN connection is VLAN tagged, then connected to an old Openreach NTE.

We know that the Openreach NTEs effectively detagged VLAN 101 and presented on the ethernet port, so this would seem to correlate to other suggestions that you're looking at QinQ tagging 4094 inside 101

Hope that helps a bit

Thank you to everyone here for all their help.

Spitfire sent me their internal guide for configuring this service on a Draytek and, combined with your guidance here, I was able to narrow down the set of variables to configure.

The QinQ is the solution as you've said; so 101 service tag as normal to talk to the FTTC kit, with a 4094 QinQ "customer" tag (in Draytek parlance) run over the Ethernet service on top.

For bridge mode, the Draytek additionally needs the bridging mode which I set to I believe the RFC 2684 IP Bridged VC Mux mode [the Draytek defaults to LLC].

All now working and the customer is happy.

Many thanks for your help.