VDSL modem/router + Raspberry Pi


I was wondering if something like the following could make any sense:

There is a relatively small number of VDSL supported router-modems, so I imagine that using an all-in-one device isn't always very convenient.

I have BT HH5A, using it as a VDSL modem, router and a switch, running OpenWrt 19.07.2 It's working fine, but I imagine if I wanted to run VPN, it would significantly affect the speed.

I have a Raspberry Pi 3 Type B lying around (not the most capable device, but could be of some service.

So I was wondering if it's possible to have the xDSL modem in the router working in bridge the mode, send the data as PPPoE to the Raspberry Pi that would then do the routing (and act as a VPN client), then send the data back on the same cable to the BTHH5A (which in this fold would act as a switch and AP (I wouldn't mind if the BTHH5A creates another subnet if necessary).

In other words, I want to re-assign the routing part of the network to the RPi, and leave the modem/switch/AP to the BTHH5A.

Does this make any sense, or do I sound like I need some rest?


Since RPi3 has faster cpu than HH5A it makes sense.
In any case, if the RPi3 is currently paperweight, you don't have much to lose trying.

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Or you might get another HH5a and have one as a modem (set up close to your DSL socket) and another as access point (set up in a middle of your house for best coverage). With RPi inbetween to serve as a VPN client.

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That makes scene. But as much as I like the HH5A for being an all-in-one solution for lightweight work, getting serial access to it was a pain in the back/backside that I don't fell thrilled by the idea of doing it again!

Yes, this can be done, it's called "one-armed router" or "router on a stick". It relies on VLAN tags to carry WAN and LAN on a single cable.

On the HH5A, disable the router functions and bridge both VLANs to the RPi:

  • Use the wan interface to bridge dsl0.X and eth0.2, and disable higher-level protocols on wan.
    For details, refer to @bill888's installation guide, section 9.8: VDSL/ADSL Bridge modem.
  • In the switch config, set up the red WAN port to carry both VLAN 1 tagged and VLAN 2 tagged.
  • Disable DHCP and DNS like on a dumb AP.
  • Make sure the IP address on the lan interface does not conflict with the RPi.
    Keep the physical interface eth0.1 for now. You could create a management VLAN separate from lan if you wanted, but let's start simple.

On the RPi:

  • Configure the wan interface to run PPPoE over eth0.2, and the lan interface to use eth0.1.
  • Connect the ethernet cable to the HH5's WAN port.

I wrote this down from memory, please adjust as needed. :wink:


Many thanks. Much appreciated.