PPPoE Modem hangup after random time - how to debug?

David Balažic
2020-04-22T17:45:12Z

Hi!

I have a router running openwrt connected to a GPON ONT, running a
PPPoE connection (hw details below).

The problem is, that after some random time one to 20 hours, the
connection breaks. Then in about a minute it reconnects (successfully,
each time).
This happens almost every day.

I enabled the debug option, but there is nothing useful in the logs:

** there is nothing related before this line **
Tue Apr 21 10:04:32 2020 daemon.notice pppd[6515]: Modem hangup
Tue Apr 21 10:04:32 2020 daemon.info pppd[6515]: Connect time 1094.4 minutes.
Tue Apr 21 10:04:32 2020 daemon.info pppd[6515]: Sent 612360704 bytes,
received 3423392867 bytes.
Tue Apr 21 10:04:32 2020 daemon.notice netifd: Network device
'pppoe-wan' link is down
Tue Apr 21 10:04:32 2020 daemon.debug pppd[6515]: Script
/lib/netifd/ppp-down started (pid 7655)
Tue Apr 21 10:04:32 2020 daemon.notice pppd[6515]: Connection terminated.
Tue Apr 21 10:04:32 2020 daemon.debug pppd[6515]: Send PPPOE Discovery
V1T1 PADT session 0x1 length 28
Tue Apr 21 10:04:32 2020 daemon.debug pppd[6515]: dst
a4:xx:xx:xx:xx:44 src c4:xx:xx:xx:xx:ed
Tue Apr 21 10:04:32 2020 daemon.debug pppd[6515]: [host-uniq 00 00
19 73] [AC-cookie ed 89 xx xx xx xx xx xx xx xx xx xx xx xx xx 75]
Tue Apr 21 10:04:32 2020 daemon.info pppd[6515]: Sent PADT
Tue Apr 21 10:04:32 2020 daemon.debug pppd[6515]: Waiting for 1 child
processes...
Tue Apr 21 10:04:32 2020 daemon.debug pppd[6515]: script
/lib/netifd/ppp-down, pid 7655
Tue Apr 21 10:04:32 2020 daemon.debug pppd[6515]: Script
/lib/netifd/ppp-down finished (pid 7655), status = 0x1
Tue Apr 21 10:04:32 2020 daemon.info pppd[6515]: Exit.

The command line is:

/usr/sbin/pppd nodetach ipparam wan ifname pppoe-wan
lcp-echo-interval 1 lcp-echo-failure 5 lcp-echo-adaptive +ipv6 set
AUTOIPV6=1 nodefaultroute usepeerdns maxfail 1 user XXXXXX password
YYYYYY ip-up-script /lib/netifd/ppp-up ipv6-up-script
/lib/netifd/ppp6-up ip-down-script /lib/netifd/ppp-down
ipv6-down-script /lib/netifd/ppp-down mtu 1492 mru 1492 plugin
rp-pppoe.so nic-eth1.3902

(the PPPoE goes over VLAN 3902, pppd version is 2.4.7)

I wrote about this on the openwrt forum [1], not much progress unfortunately.

Any ides? How to proceed? Sniff packets?

What does normally prompt pppd to to print "Modem hangup" ?

Thanks in advance,
David

[1] https://forum.openwrt.org/t/pppoe-disconnects-every-few-hours/61239

Setup details:

ONT: Innbox G21 (provided by ISP)
router: Netgear WNDR 3700v2 running OpenWRT 19.7.2
ISP provided router (not in use): Ubee TVW625 - I did not see such
disconnections when using this router (I ran a script calling ping in
a loop, for days, logging output, not problem except a lost (single)
packet every now and then)