In these days, I'm trying to configure my FritzBox 7530 with OpenWrt and my DSL connection.
I installed the latest snapshot available, OpenWrt SNAPSHOT, r23051-d6fef27f2d.
Following the instructions in the wiki, I installed the VRX512 firmware.
I see that the firmware is loaded:
Reading again, valid Annexes for VDSL2 seem to be A, B or C, depending on your region.
But I have Annex J in my config and it correctly seems to fall back to B upon synchronization.
So for VDSL2 in Europe setting either Annex B or J should work fine.
AnnexJ is an ADSL thing, for VDSL2 Annex A-C contain the regional specialities (e.g. bandplans and PSD masks, ...) with Annex A for Region A (North America), Annex B for Region B (Europe), and Annex C for Region C (Japan), I assume the rest of the world picks either of these... see ITU-T G.993.2 for the gory details...
Side-note: ADSL also had Annex A and B but there these actually specified different bandplans, with Annex A being tailored to harmonize with a few KHz POTs band at the beginning, and Annex B tailored to leave more room at the beginning for ISDN.
I have an update, I was able to connect to internet using only one of the LAN ports and not the WAN one.
Firstly, let me say that I don't have a "physical" analogic DSL connection, but I have a fixed wireless access that was working with stock firmware, PPPoE connection on LAN1 of the FritzBox.
I was able to configure lan4.100 for internet access, excluding it from br-lan, as follows:
With this config, I'm able to reach internet successfully and the new internet interface is named pppoe-wan.
Instead, if I connect the antenna cable to the WAN port, even if I configure dsl0, dsl.100 or dsl0.100, I have the device not found error.
At this point, maybe I'm overcomplicating things: as the real "modem" is the antenna, which I connected from the FritzBox via PPPoE (LAN ports), should I still need the DSL drivers? If yes, why can't I use the WAN interface? The config is the same, as I'm able to use the lan4 port to connect.
If DSL drivers are not required, and I can only use one of the LAN ports to connect, is my configuration clean/optimized enough?
OK, the "WAN" port is connected to a DSL modem, no big surprise that this does not work when connected with something not actually using DSL.
Your solution, re-dedicating one of the LAN ports as ethernet WAN port is as far as I can tell, exactly the correct solution. (The question then is: why use a DSL-router at all, but I assume you had this sitting around or got one cheaply)
Internally, there is no such thing as a dedicated WAN port. Your device has a four-port switch and you can use and assign any port the way you like it. WAN on OpenWrt only refers to the firewalling zone, not to a specific port. In fact, it doesn't matter how your interfaces are named as long as they are contained in the correct firewalling zone.
That said, I'm also using a FRITZ!7520 as my main router with a cable modem - for historic reasons, we switched from DSL to cable just a few weeks ago. I have a very similar configuration with the only exception that I use lan4 as device for wan as I don't need to use VLAN 100 (well, actually my interface is called cable and it's lan1, but that doesn't make a real difference).
If you're not using the internal DSL modem, you're just using the device as a router and don't need the DSL files (you could in fact have used the standard 22.03.x firmware). The ipq40xx switch has some hardware oddities related to VLANs so there might be no clear answer how AVM got LAN1 to work as the WAN; as you've got LAN4 working as the WAN consider that a win and don't worry about LAN1 not working as the WAN.