L2TP client in ePMP CPEs

Hello. My name´s Pedro Dominguez and I works in Vivacable engineering department. Vivacable is a FTTH and wireless ISP from the South of Spain, with around 15000 customers. In wireless networks we started to use Cambium ePMP devices around three years ago. We have around 700 ePMP CPEs deployed. 

We configure ePMP CPEs in NAT mode and we use PPPoE at them. ePMP CPEs are connected through a bridged network (layer 2) to Mikrotiks PPPoE servers, using Radius authentication. In the bridged network we use different manufacturers devices, Cambium, Ubiquiti, Mimosa,.... We use Spanning Tree in order to have rings for redundancy, but it doesn´t work fine at all. 
In the engineering department we are studying the possibility to use L2TP instead off PPPoE . The idea is to be able to have a routed network (layer 3) between ePMP CPEs and Mikrotiks L2TP servers, in order to be able to use layer 3 redundancy protocols.

The key question is if Cambium has in his roadmap to include a L2TP client in ePMP CPEs. For the moment we are testing this L2TP topology using Cambium CPEs in bridge mode and running L2TP in TPLink customer routers (after Cambium CPEs). But this way requires to allocate Cambium CPEs with management IPs (instead of public IPs), and complicates a lot the network management.

Thank you very much and best regards, 
Pedro Dominguez 
VIVACABLE, dpto Ingenieria 
Avda. del Comercio 41-43, PI Poliviso 
41520 El Viso del Alcor – Sevilla 
0034 672 240 542

Why not just add a Mikrotik for PPPoE server at each tower ? After that, you can use L2TP, MPLS or whatever you want to hide your network up to your core.

Hi Mike, thank you for your comment.

We already had considered this option, also tested in field, but the main inconvenience is related to the necessary public IP ranges large splitting in this case:

We use Mikrotik PPPoE connections to provide a public IP to each Cambium CPE at final customer. At this moment we have 5 Mikrotik PPPoE servers, each one providing PPPoE connections in each one of the 5 bridged layer 2 networks that we have divide our complete wireless net. Our complete wireless net includes around 50 towers for around 700 Cambium CPEs and around 1500 Ubiquiti CPEs.

If we add a Mikrotik for PPPoE server at each tower, we would need around 50 MIkrotik servers and to split our public IP ranges in 50 subranges. This means to lose a lot of public IPs in the splitting, and also leaving available not used IPs in each subrange for our day a day growing.

This is the reason why we discard this option and we started to think in others solutions.

Thanks again and regards