Solved PPPoE failing with "Timeout waiting for PADO packets"

[lluke]

Hi All,
I've just completed the switch to a new FTTH provider here in my country (Italy). Unfortunately, after the switch I'm not able anymore to establish a PPPoE connection with my ASUS RT-AC86U due to the error "Timeout waiting for PADO packets".
I've made the tries with both the latest Asus firmware (3.0.0.4.386.48260) and the Merlin one (386.5_2).

With the same network setup, the connection is successfully established using a FRITZ!Box 7530.

The network is structured as below:

Internet --(optical fiber)--> ZTE GPON ONT --(ethernet)--> Router


The requirements from the provider are:

• Username, configured from WAN page: openfiber
• Password, configured from WAN page: openfiber
• Protocol, configured from WAN page: PPPoE Routed (as defined in RFC 2516)
• Encapsulation, I'm not seeing any place where to enable it: VLAN Ethernet 802.1q
• NAT, configured from WAN page: enabled
• VLAN, configured from WAN page: 835

The error I'm getting looking at the logs is the following:

May  5 07:05:05 kernel: 8021q: 802.1Q VLAN Support v1.8
May  5 07:05:05 kernel: Broadcom 802.1Q VLAN Interface, v0.1
May  5 07:05:15 pppd[2534]: Plugin rp-pppoe.so loaded.
May  5 07:05:15 pppd[1281]: RP-PPPoE plugin version 3.11 compiled against pppd 2.4.7
May  5 07:05:15 pppd[1285]: pppd 2.4.7 started by admin, uid 0
May  5 07:05:40 avahi-daemon[1595]: Joining mDNS multicast group on interface vlan835.IPv4 with address 169.254.45.14.
May  5 07:05:40 avahi-daemon[1595]: New relevant interface vlan835.IPv4 for mDNS.
May  5 07:05:40 avahi-daemon[1595]: Registering new address record for 169.254.45.14 on vlan835.IPv4.
May  5 07:07:10 pppd[2442]: Timeout waiting for PADO packets

I really need your help to solve this situation because moving from ASUS wrt Merlin to the FRITZ!OS has been really a pain so far.

If needed and you can drive me also to debug the connection between the router and the ONT I've some tech and networking skills and I'll do any kind of test you may suggest.

 

[lluke]

I've finally found the issue and it is related to the following factors:

- Host-Uniq required value, not specified by my ISP
- VLAN should be empty instead of 835

Just for the sake of curiosity of people that may deal with the same issue in the future: to identify the problem I've connected my routers (the one able to connect and the one failing) to my laptop and analyzed the PPPoE requests through Wireshark.
It is definitely the easiest way to identify what the non-working router is doing wrongly.

About the Host-Uniq worth to know is that Asus added a 32 chars limitation so that if your ISP is using a longer one you should find a way to workaround it (e.g. I'm temporarily using the ISP router for the PPPoE connection only and the Asus one for the internal LAN routing)