Using a FritzBox as a modem and connecting another FritzBox

I have a Zen supplied FritzBox 3490 (never used, now confirmed working) and a FritzBox 7490 connected to Zen and with bespoke settings for my network.

What I want to do: Use the 3490 as a modem, connect the 7490 to it and continue using its settings other than the DSL connection. (Don't ask why, just accept!)

I tried a couple of settings then, when that wasn't working, went and RTFM.

AVM say "The FRITZ!Box cannot be used as a simple DSL modem" which kinda puts a spanner in my works.

So before I spend all day without a working internet: are AVM being cautious, or is there really no way to use the 3490 (or any FritzBox) as a modem?

I just set up a 7530 as a "modem", sort of. My EdgeRouter-X uses PPPoE to get the WAN address and do the NAT.

What you're suggesting sounds like you want to have a Double NAT situation. Usually everyone advises against this. I've done that back when I first had Sky Fibre years ago and their Hubs were restrictive, it was problematic, yes, but it worked.

Can you set your 7490 to get DHCP from the 3490?

In reply to a post by Saltank:

Can you set your 7490 to get DHCP from the 3490?

Yes, but then the 7490 will be on 192.168.178.n rather than 192.168.1.n which I'm using. I guess I could change the subnet on the 3490...

But no matter. I've found an old ECI modem, plugged it in and it genuinely "just worked"! It was supplied by Zen many years ago so will have had my credentials saved.

I can use this instead of the FritzBox, don't think I lose anything this way other than access to the DSL stats which are either unavailable or I don't know how to access them.

If it's the ECI box I'm thinking of, it is unlikely to have any credentials saved. It acts just as a modem, and the PPPoE all still happens in your router that you connect to it.

In reply to a post by jimbof:

If it's the ECI box I'm thinking of, it is unlikely to have any credentials saved. It acts just as a modem, and the PPPoE all still happens in your router that you connect to it.

I think you are correct. I tried using one of the FritzBoxes without my Zen credentials and no interwebs! Is there really no way of seeing the current DSL connection speed and other exciting data the FritzBox provides on the ECI? Is it really just a dumb modem?

In reply to a post by Woolwich:

I think you are correct. I tried using one of the FritzBoxes without my Zen credentials and no interwebs! Is there really no way of seeing the current DSL connection speed and other exciting data the FritzBox provides on the ECI? Is it really just a dumb modem?

Not without some kind of hack to the unit (I'm not even 100% sure there was a hack for the ECI). forum.kitz.co.uk is probably the best site to find out about that.

If you want an out-of-box VDSL modem that you can get lots of stats out of, you can use a Draytek Vigor V130. It has basic info on the web interface, and a lot more detailed info via an ssh interface.

For advanced use it can also I believe (I haven't set one up like this) act as a PPPoE client - and when used like this it bridges the public IP onto the LAN interface for a router to connect to without having to do PPPoE itself. That may mean the router loses the PPPoE overhead.

I know you said "don't ask", but not really sure what the benefit is that you are trying to extract using an external modem, particularly if the Fritz has the kind of info you need. Most of the time you'd use an external modem to act as a modem because you needed it to use a particular router which otherwise couldn't connect to the incoming service.

Following is an example of the command like stats I can get from my Vigor 130:

vdsl status
---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
Running Mode : 17A State : SHOWTIME
DS Actual Rate : 79995000 bps US Actual Rate : 20000000 bps
DS Attainable Rate : 92278328 bps US Attainable Rate : 25681007 bps
DS Path Mode : Fast US Path Mode : Fast
DS Interleave Depth : 1 US Interleave Depth : 1
NE Current Attenuation : 10 dB Cur SNR Margin : 4 dB
DS actual PSD : -2.-9 dB US actual PSD : -2.-7 dB
NE CRC Count : 0 FE CRC Count : 1505
NE ES Count : 0 FE ES Count : 1287
Xdsl Reset Times : 0 Xdsl Link Times : 13
ITU Version[0] : fe004452 ITU Version[1] : 41590000
VDSL Firmware Version : 05-07-06-0D-01-07 [with Vectoring support]
Power Management Mode : DSL_G997_PMS_L0
Test Mode : DISABLE
-------------------------------- ATU-C Info ---------------------------------
Far Current Attenuation : 7 dB Far SNR Margin : 9 dB
CO ITU Version[0] : b5004946 CO ITU Version[1] : 544eb206
DSLAM CHIPSET VENDOR : < IFTN >
> vdsl status more
vdsl status more
---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
Near End Far End Note
Trellis : 1 1
Bitswap : 0 0
ReTxEnable : 0 0
VirtualNoise : 0 0
20BitSupport : 0 0
LatencyPath : 0 0
LOS : 2 0
LOF : 0 0
LPR : 0 0
LOM : 0 0
SosSuccess : 0 0
NCD : 0 0
LCD : 0 0
FECS : 0 26313 (seconds)
ES : 0 1287 (seconds)
SES : 0 13 (seconds)
LOSS : 0 61 (seconds)
UAS : 40 437 (seconds)
HECError : 0 0
CRC : 0 1505
RsCorrection : 0 0
INP : 0 0 (symbols)
InterleaveDelay : 0 0 (1/100 ms)
NFEC : 255 255
RFEC : 16 16
LSYMB : 5410 21451
INTLVBLOCK : 255 255
AELEM : 0 ----

In reply to a post by jimbof:

I know you said "don't ask", but not really sure what the benefit is that you are trying to extract using an external modem, particularly if the Fritz has the kind of info you need.

The TL;DR is I want to move the router nearer to the Openreach entry point thus removing 12-15 metres of internal cable with the hope of better speeds. But I can't move the router because of my LAN cabling. But with a separate modem and the FritzBox in its current position and making use of an existing Ethernet, I can be in business.

Full story is here

Spoiler alert: I tried and it made no difference to my speeds.

In reply to a post by Woolwich:

Is there really no way of seeing the current DSL connection speed and other exciting data the FritzBox provides on the ECI? Is it really just a dumb modem?

Various auction sites will probably still have the Huawei HG612 which was the alternative Openreach modem. These can be modified to use the second Ethernet port for access to the diagnostic data.

I am using a FB7530 as a modem using the Ppoe pass through feature to a 2nd router. As my supplier only allows one conection I had to put dummy dsl user details in the FB7530. I am using port forwarding in my 2nd router and there is no double nat.