XS4ALL and probably KPN

source: https://openwrt.org/docs/guide-user/network/wan/isp-configurations

XS4ALL is another ISP from KPN like Telfort. They offer DSL and FTTH connections. For DSL it is possible to use your own router, but since latest techniques use profile 35b to get 200+ Mbit speeds over a single line, it's better (for speed) to put the provided FritzBox in bridge mode and use OpenWrt as if directly on FTTH connection.
Internet

FTTH (Fibre) and VDSL connections result in VLANs 6, and 4. That is, connecting the ethernet cable from the fibre's NTU or from the bridged VDSL modem, to your WAN port does nothing by itself. Internet is provided over a PPPoE connection over VLAN6, username and password don't matter here, as long as they are set. Thus, to bring up your WAN device which gets your public IP addresses (XS4ALL does both IPv4 and IPv6), configure like this:

config interface 'wan'
    option ifname 'eth0.6'
    option proto 'pppoe'
    option username 'FB7581@xs4all.nl'
    option password '1234'
    option ipv6 'auto'
    option mtu '1508'  # only works for FTTH since FritzBox doesn't support higher MTU

config interface 'wan6'
    option proto 'dhcpv6'
    option reqaddress 'try'
    option reqprefix 'auto'
    option ifname '@wan'

Telephony

If you use telephony and use FTTH, easiest is to connect the (unused) provided FritzBox as regular client to your OpenWrt lan. You can configure the FritzBox to take internet from there and provide telephony (which is just SIP).
IPTV

If you use TV, in the old setup (before March 2019) you could just bridge VLAN4 to your STBs (the black receivers provided by XS4ALL). This is called bridged mode. However, starting from March 2019, bridged mode is no longer provided and instead, routed mode has to be setup. The obvious change visible is the additions of “interactive TV” in the STBs. Routed mode, is much like described in IPTV / UDP multicast. It has a small specific twist for XS4ALL though. The official documentation for this can be found at XS4ALL's modem setup (Dutch).

For this to work, you need to install igmpproxy. For clarity, we use 3 different zones: wan, iptv and stbitv.

    wan: the ordinary internet connection, used for “interactive” features (e.g. YouTube)
    iptv: VLAN4-based connection, mostly used for multicast based live-streams, and STB software, some 10.200.x.x/22
    stbitv: the (client) network with the STBs in them, in this example 10.3.0.0/24

First, configure an interface, DHCP client for iptv, the VLAN 4 interface. Important, it needs to set Vendor Class Identifier to IPTV_RG, and ignore any default gateway or dns servers advertised. The DNS is bogus (per the docs), the default route is what we don't want to use, because we want to use our real internet connection. In the DHCP reply is an additional route, you don't see this in luci, but it's correctly added to your routing table, and it basically includes all the traffic that needs to go over VLAN 4. This is basically why we don't need the default route.

config interface 'iptv'
    option type 'bridge'
    option ifname 'eth0.4'
    option proto 'dhcp'
    option defaultroute '0'
    option peerdns '0'
    option vendorid 'IPTV_RG'

Also create a firewall zone for this interface, that sets masquerading (like wan, we need to NAT some traffic over this interface):

config zone
    option name 'iptv'
    option input 'ACCEPT'
    option output 'ACCEPT'
    option network 'iptv'
    option masq '1'
    option mtu_fix '1'
    option forward 'REJECT'

Next, configure a new interface for the STBs. I isolated them on their own VLAN 7, but I think you could also plug them into an existing client network. Since there will be multicast traffic over this, you do want to separate the traffic using igmp snooping. Ensure you enable this, and if you use switches inbetween that they also enable this, else you'll flood your entire network. This is particularly bad if you have wlans in your network. The following is just what I used for this description.

config interface 'stbitv'
    option type 'bridge'
    option proto 'static'
    option ifname 'eth0.7'
    option ipaddr '10.3.0.1'
    option netmask '255.255.255.0'
    option igmp_snooping '1'

The STBs don't need any special DHCP tricks, so you just need to hand out IPs in the normal way. Only IPv4 is supported. Create firewall zone for this network, and “glue” that zone together with the iptv and wan zones, such that traffic can go both ways:

config zone
    option input 'ACCEPT'
    option forward 'REJECT'
    option output 'ACCEPT'
    option name 'stbitv'
    option network 'stbitv'

config forwarding
    option dest 'wan'
    option src 'stbitv'

config forwarding
    option dest 'iptv'
    option src 'stbitv'

Now, the last remaining bit needs to be done, which is forwarding the multicast packets that the STBs request. Since the OpenWrt router now is the terminating node as seen from the XS4ALL network, any multicast traffic arriving at the router, needs to be forwarded to the STB in the network that requested it. This is done by igmpproxy. For the proxy, upstream is the XS4ALL network, downstream the STBs in the client network. Quickleave feature is necessary to quickly terminate unnecessary streams (happening when switching between channels, “zapping”). As such, the following configuration is sufficient:

config igmpproxy
    option quickleave 1

config phyint
    option network iptv
    option zone iptv
    option direction upstream
    list altnet 0.0.0.0/0

config phyint
    option network stbitv
    option zone stbitv
    option direction downstream

Final remaining thing is to enable and start igmpproxy using /etc/init.d/igmpproxy enable and /etc/init.d/igmpproxy start.

Once you applied all this, ensure you got a 10.200.x.y IP address on the iptv interface. Check with netstat -rn that there is a route for destination 213.75.112.0 (could be slightly different) added with gateway your 10.200.x.1 IP address. Interface should be br-iptv if you followed above example. If that seems ok, and igmpproxy is running, shutdown your STBs and restart them. They should come up quite normal and settings/system should now report “routed mode”. If you get any errors reported by the devices, check the multicast traffic gets forwarded (it attempts this while STB boots) using tcpdump or something. Also check if regular internet works correctly from the STB client network.

source: https://openwrt.org/docs/guide-user/network/wan/isp-configurations