ftth-tiscali-no-modem/README.md

# FTTH Tiscali without modem

This is a short guide on how to connect your Linux box to the Internet using directly the GPON provided by Tiscali.

## TL;DR

You just need `pppd` and a virtual Ethernet device. The latter is created with:

`ip link add link eth0 name eth0.835 type vlan id 835`

assuming your ethernet device is `eth0`.

Credentials for PPPoE can  be obtained [here for Tiscali](https://assistenza.tiscali.it/supporto/moduli/servizi/modem-libero/). You can also sniff the [CHAP](https://en.wikipedia.org/wiki/Challenge-Handshake_Authentication_Protocol) authentication and crack it, the password is just 6 numeric characters.

To connect to the PPPoE server, install `pppd` and configure it

##### /etc/ppp/peers/tiscali

```
plugin pppoe.so
# rp_pppoe_ac 'your ac name'
# rp_pppoe_service 'your service name'

# network interface
eth0.835
# login name
name "NAME.SURNAME@tiscali.it"
usepeerdns
persist
# Uncomment this if you want to enable dial on demand
#demand
#idle 180
defaultroute
hide-password
noauth
```

and

##### /etc/ppp/chap-secrets

```
# Secrets for authentication using CHAP
# client                        server  secret                  IP addresses
"NAME.SURNAME@tiscali.it"       *       "123456"
```

(replace 123456 with your password)

Finally you can switch on the service with:

```
ppp call tiscali
```

and then use `journalctl -f` to check whether things are going fine.

Systemd automation can be created with the help of [these scripts](https://gitlab.com/jimdigriz/debian-clearfog-gt-8k/-/blob/master/README.md).

## Long Story

The FFTH service comes with a **GPON** ([gigabit-capable passive optical network](https://en.wikipedia.org/wiki/G.984)), and I wanted to connect the PC with my self hosted services directly to its ethernet port, bypassing the big black box (ZTE H388X a.k.a. ZTE Modem Tim Hub+) customized with some mysterious proprietary firmware from TISCALI (I asked, of course they don't share it).

Needless to say, using the credentials that TISCALI gave me directly with `pppd` on my ethernet interface did not work. The logs and the error messages are

```
pppd[1336]: Plugin pppoe.so loaded.
pppd[1336]: PPPoE plugin from pppd 2.4.9
pppd[1337]: pppd 2.4.9 started by pie, uid 0
kernel: NET: Registered PF_PPPOX protocol family
pppd[1337]: Timeout waiting for PADO packets
pppd[1337]: Unable to complete PPPoE Discovery
```



For some reason, nobody replied with an *Offer* (PADO) to my request for a PPP *Initiation* (PADI). Not much gained from the error message, so the only way to find how to talk to the PPPoE server is to collect a working setup.

I managed to sniff the traffic between the modem and the GPON with this fantastic Ethernet Hub from the 90s!

![HUB](README.assets/hub1.jpeg)

The approach is [like this](https://wiki.wireshark.org/CaptureSetup/Ethernet#capture-using-an-ethernet-hub):

![](README.assets/Capture-switch-hub-ws.png)



The packets captured just after powering on the ZTE H388X are shown here:

![packets](README.assets/packets.png)

There are basically three steps:

* Red box: a termination request. Probably to clean up everything before starting a new session.
* Yellow box: the PPP Initialization starts from the ZTE and is followed by an Offer from the Cisco server.
* Green box: the authentication, with CHAP protocol.

When using `pppd`, the cleanup part is missing and the first packet is a PADI, which looks exactly like the one in packet No. 7 above, except for the 802.1Q part shown by the blue arrow. That was indeed the trick: the server replies only when the PADI request comes from a VLAN with ID 835.

Creating the vlan with

```
`ip link add link eth0 name eth0.835 type vlan id 835`
```

and setting it as the device for the PPP connection makes the Cisco server happy: it promptly replies to our PADI packet and the connection is setup in less than a second.