How to decipher, why the pppoe interface has disconnected?

Question

I am using a Ubiquity Edgerouter X, which is connected to a Draytek modem. This is the log from the pppoe interface:

#######@ubnt:~$ show interfaces pppoe pppoe0 log
Tue Jun 13 06:26:00 IST 2017: PPP interface pppoe0 created
Tue Jun 13 06:26:01 IST 2017: Stopping PPP daemon for pppoe0
Tue Jun 13 06:26:02 IST 2017: Starting PPP daemon for pppoe0
Connected to 00:d0:f6:c9:5e:f9 via interface eth0
using channel 1
Using interface ppp0
Connect: ppp0 <--> eth0
sent [LCP ConfReq id=0x1 <mru 1492> <magic 0xeb709638>]
rcvd [LCP ConfAck id=0x1 <mru 1492> <magic 0xeb709638>]
sent [LCP ConfReq id=0x1 <mru 1492> <magic 0xeb709638>]
rcvd [LCP ConfAck id=0x1 <mru 1492> <magic 0xeb709638>]
rcvd [LCP ConfReq id=0x55 <mru 1492> <magic 0x4f89f808>]
lcp_reqci: returning CONFACK.
sent [LCP ConfAck id=0x55 <mru 1492> <magic 0x4f89f808>]
sent [LCP EchoReq id=0x0 magic=0xeb709638]
peer from calling number 00:D0:F6:**:**:** authorized
sent [IPCP ConfReq id=0x1 <addr 0.0.0.0> <ms-dns1 0.0.0.0> <ms-dns3 0.0.0.0>]
rcvd [IPCP ConfReq id=0xbc <addr 86.***.***.***>]
ipcp: returning Configure-ACK
sent [IPCP ConfAck id=0xbc <addr 86.***.***.***>]
rcvd [IPV6CP ConfReq id=0x2 <addr fe80::02d0:f6ff:fec9:5d80>]
Unsupported protocol 'IPv6 Control Protovol' (0x8057) received
sent [LCP ProtRej id=0x2 80 57 01 02 00 0e 01 0a 02 d0 f6 ff fe c9 5d 80]
rcvd [IPCP ConfNak id=0x1 <addr 86.***.***.***> <ms-dns1 159.134.0.1> <ms-dns3 159.134.0.2>]
sent [IPCP ConfReq id=0x2 <addr 86.***.***.***> <ms-dns1 159.134.0.1> <ms-dns3 159.134.0.2>]
rcvd [LCP EchoRep id=0x0 magic=0x4f89f808]
rcvd [IPV6CP TermReq id=0x3]
Unsupported protocol 'IPv6 Control Protovol' (0x8057) received
sent [LCP ProtRej id=0x3 80 57 05 03 00 04]
rcvd [IPCP ConfAck id=0x2 <addr 86.***.***.***> <ms-dns1 159.134.0.1> <ms-dns3 159.134.0.2>]
ipcp: up
Script /etc/ppp/ip-pre-up started (pid 1537)
Script /etc/ppp/ip-pre-up finished (pid 1537), status = 0x0
local  IP address 86.***.***.***
remote IP address 86.***.***.***
primary   DNS address 159.134.0.1
secondary DNS address 159.134.0.2
Script /etc/ppp/ip-up started (pid 1592)
rcvd [IPV6CP TermReq id=0x4]
Unsupported protocol 'IPv6 Control Protovol' (0x8057) received
sent [LCP ProtRej id=0x4 80 57 05 04 00 04]
Script /etc/ppp/ip-up finished (pid 1592), status = 0x0
rcvd [LCP ConfReq id=0x10 <mru 1492> <magic 0x798f51e9>]
ipcp: down
Connect time 1741.9 minutes.
Sent 127000962 bytes, received 396463381 bytes.
Script /etc/ppp/ip-down started (pid 23303)
sent [LCP ConfReq id=0x5 <mru 1492> <magic 0xb97c6200>]
lcp_reqci: returning CONFACK.
sent [LCP ConfAck id=0x10 <mru 1492> <magic 0x798f51e9>]
rcvd [LCP TermReq id=0x56]
sent [LCP TermAck id=0x56]
sent [LCP ConfReq id=0x5 <mru 1492> <magic 0xb97c6200>]
Script /etc/ppp/ip-down finished (pid 23303), status = 0x0
sent [LCP ConfReq id=0x5 <mru 1492> <magic 0xb97c6200>]
sent [LCP ConfReq id=0x5 <mru 1492> <magic 0xb97c6200>]
sent [LCP ConfReq id=0x5 <mru 1492> <magic 0xb97c6200>]
... repeats

I don't understand why the device disconnects upon receiving rcvd [IPCP ConfReq:

rcvd [LCP ConfReq id=0x10 <mru 1492> <magic 0x798f51e9>]
ipcp: down

I am interpreting the log correctly?

The device will then drop its pppoe connection and sends LCP ConfReq-s in a loop. If I restart the pppoe interface, the connection comes back up. Which, to my knowledge, will again send an LCP ConfReq - how could it this time succeed?

EDIT:

Also, there is no CHAP or PAP authentification succeeded, yet the connection is up?

Answer 1

This turned out to be a bug in the OS of the router. It would get itself stuck in a loop and drop its PPPoE.

As a quick fix I added a script that would clear the PPPoE interface, and placed it here:

/config/scripts/ppp/ip-down.d

The script would then be ran when the PPPoE connection drops. Clearing the interface would then restart the connection and it would be fine again (24 hours approx) until the problem re-emerged.

It works until the manufacturers sort out the above issue.