OK, so here goes....

I have 4 x VDSL lines (3 with one provider, 1 with a different provider) which I would like to use as follows:

Leave my existing router / firewall (Netgear D7000) on the "old ISP" with DHCP running, for the general devices and children in the house to use.
Use the other 3 lines and bond using MLPPP.

I have 3 x Netgear DM200 modems, which act as router or "modem only". They are currently set to "modem only" and have private IPs on the same subnet.

I want to achieve the bonding of three lines as MLPPP (it's enabled on the ISP, being my own company) and fail over to the "old ISP" if something goes drastically wrong at the ISP DSLAM etc.

I would like to also utilise the bonded set of lines *and* the existing "old ISP" for downloading, either via an OpenVPN bridge directly from each PC, or preferably the ClearOS router itself, so I don't need to run VPN clients on all devices that require ultra fast access.

This setup should give me circa 300mbit download and upload which is roughly the sum of the three bonded lines (I fully understand I won't be able to use the fourth connection as aggregate upload if I'm not VPN'd....)

Bandwidth really isn't a problem as we have a 400Gbit + BGP network and multiple Cisco and Juniper devices scattered arond the country, my question is if this can be done on ClearOS or should I start manually building something up on Ubuntu?

I've been playing with Cisco 2901 and Juniper SRX devices (The latter don't do MLPPP at all, be warned) but cannot get any sensible throughput on hardware devices around £1k with NAT enabled. Seems a pity to waste the hardware when I have plenty of network cards, Xeon boxes with RAM and storage lying around....

Shameless plug here as well but if any forum users require Dedicated Servers, VPN, Colocation or FTTC lines, please feel free to hit me up.

Cheers!