VOO in bridge mode with IPv6 (optional: and prefix delegation!)

Despite old threads that can be seen on VOO’s forum, VOO do not seem to use SLAAC in bridge mode (anymore?), but DHCPv6. Also VOO only gives a /64 prefix so you can’t do internal subnets 🙁

Important: my outgoing (WAN) interface directly connected to the VOO modem in bridge mode is enx000ec6ec03b3 . My internal LAN interface is br0 (it’s a bridge between my actual eth0 LAN interface and a WiFi access point using hostapd, but that’s for another day).

This tutorial assumes Ubuntu 18.04:

sudo apt install wide-dhcpv6-client

sudo vi /etc/wide-dhcpv6/dhcp6c.conf

interface enx000ec6ec03b3 {
  send ia-na 1;
  send ia-pd 1;
  request domain-name-servers;
  request domain-name;
  script "/etc/wide-dhcpv6/dhcp6c-script";

# Only for prefix delegation
id-assoc pd 1 {
  prefix-interface br0 { #internal facing interface (LAN)
    sla-id 0; # subnet. Combined with ia-pd to configure the subnet for this interface.
    ifid 1; #IP address "postfix". if not set it will use EUI-64 address of the interface. Combined with SLA-ID'd prefix to create full IP address of interface.
    sla-len 0; # Number of prefix bits assigned. Sadly this is 0 with voo... 

  id-assoc na 1 {
  # id-assoc for eth1

sudo vi /etc/default/wide-dhcpv6-client


sudo service wide-dhcpv6-client restart

At this point you should get an IPv6 address:

enx000ec6ec03b3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 109.89.XXX  netmask  broadcast 109.89.XXXX
        inet6 2a02:2788:XXXXXXXXX:8458  prefixlen 128  scopeid 0x0<global>
        inet6 fe80::20e:c6ff:feec:3b3  prefixlen 64  scopeid 0x20<link>
        ether 00:0e:c6:ec:03:b3  txqueuelen 1000  (Ethernet)
        RX packets 1358557038  bytes 1701875645905 (1.7 TB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 648168501  bytes 176987273193 (176.9 GB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Enable prefix delegation

Actually enable the prefix delegation with radvd:

sudo apt-get install radvd

sudo vi /etc/radvd.conf

interface br0 # LAN interface
  AdvManagedFlag off; # no DHCPv6 server here.
  AdvOtherConfigFlag off; # not even for options.
  AdvSendAdvert on;
  AdvDefaultPreference high;
  AdvLinkMTU 1280;
  prefix ::/64 #pick one non-link-local prefix assigned to the interface and start advertising it
    AdvOnLink on;
    AdvAutonomous on;

sudo service radvd restart

Some configuration is taken and adapted from https://www.ipcalypse.ca/?p=204

Proximus BBOX 3 in bridge mode with prefix delegation on Linux

Using bridge mode allows you to get a public IP address on one computer (which can serve as a router) behind your modem. This allows you to know your public IP address without using a third-party service, and control more finely all your routing parameters inside your own Linux-based router (this tutorial) or a better router than the BBOX’s one.

We’ll call “the router” the device you want to use behind the modem for clarity.

The bridge mode of the Proximus BBOX 3 is quite interesting. You connect normally to your BBOX using DHCP and will get a locally routable address (i.e., but you can use PPP over Ethernet (PPPoE) to get a virtual interface inside your router. This virtual “ppp” interface will have a public IP address, and packets will flow IN and OUT the internet through that interface.

Proximus allows you to therefore maintain 2 PPP connections, one established by the BBOX (also used for the TV), and the other inside your router. It also means your home gets 2 IPv4 addresses.

I prefer that mode to the VOO one, where the external IP address is given by DHCP to only one host in the LAN, the first device to connect to the router using DHCP (dangerous and prone to configuration errors...). Same and independently for IPv6 using DHCPv6. While Proximus not only gives you an IPv6 address but also a /64 prefix via PPPoE to get a direct connection without using a crappy NAT to all your PCs. For IPv6, Proximus is much simpler than setting up an independent DHCPv6 client which gives back the v6 prefix to your LAN side. The second downside is that VOO must use ugly hacks to allow connection to the box as there is no "modem internal network" anymore. You can access your modem at the normally-illegal address as this is on the "public web" space from the router perspective. Moreover, it seems that the modem stops responding to DHCP requests from time to time, losing connectivity... VOO bridge mode is definitively not good... But this may be a temporary bug. I did not observe this anymore...

The bridge/WAN part

Edit /etc/network/interfaces to add the following lines , assuming that eth0 is the interface used to connect to your BBOX.

auto dsl-provider
 iface dsl-provider inet ppp
 pre-up /bin/ip link set eth0 up
 provider dsl-provider

Install pppoe with sudo apt-get install pppoe on ubuntu/debian or sudo yum install pppoe centos/fedora

Then create a file named /etc/ppp/peers/dsl-provider and add the following lines :

mtu 1492
plugin rp-pppoe.so eth0
user "fc0123456@skynet"

Then edit the file /etc/ppp/chap-secrets and add the line :
"fc012345@skynet" * "password"

If you lost your skynet credentials (personally, I just never received them), you can change them online on MyProximus. You’ll have to reboot your modem so it receives automatically the new credentials.

And that’s all, you can reboot or do a sudo pon dsl-provider and you’ll have a new interface with a public IPv4 and a /64 IPv6.

The router/LAN part

To give connectivity in IPv4 for your hosts and use your Linux host as a router, you’ll have to do a NAT. But you can delegate your IPv6 range and give public IPv6 addresses to all your PCs using SLAAC! Remember to also install a firewall…

To do so, install radvd and add in /etc/radvd.conf (if br0 is the interface connected to your internal network) :

interface br0

 AdvSendAdvert on;
 prefix ::/64
   AdvOnLink on;
   AdvAutonomous on;
   AdvRouterAddr on;
 RDNSS 2001:4860:4860::8888 2001:4860:4860::8844
   # AdvRDNSSLifetime 3600;

Then do a sudo radvd restart and that’s it.

The RDNSS line gives the address of Google’s public DNS to your host. We could use Proximus’ one, but I don’t have the address on hand.

Do not hesitate to contact me!