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Equipment:

Fedora 27 x86_64
Technicolor C2100T DSL modem/router
Unknown Centurylink ONT optical adapter`

I recently switched from CL 80mb DSL to CL 1000mb fiber, which still relies on pppoe. I have always used a basic Linux Fedora machine as the router/firewall with the DSL modem in bridging mode. The installer claimed no changes to my router would be needed when he arrived. But when it came time to activate after the install, the Fedora pppd would not connect, even though the credentials didn't change from DSL to fiber.

Finally as he was getting anxious to move on to the next appointment, so I switched the C2100T modem in to routing mode to let it perform the ppp credentials, and everything worked fine; same credentials. So I made some simple changes to the Fedora box to route through the modem and he left. But in the week since, I'm still unable to find the correct solution to get back to bridging mode, and ultimately to remove the C2100T all together and hook the ONT directly to my Fedora box.

The only errors are messages like this in /var/log/messages:

Aug 24 16:59:24 murdock network[28969]: Bringing up interface ppp0: [ OK ]
Aug 24 16:59:24 murdock pppd[29379]: pppd 2.4.7 started by root, uid 0
Aug 24 16:59:24 murdock NetworkManager[685]: [1566683964.9027] manager: (ppp0): new Generic device (/org/freedesktop/NetworkManager/Devices/64)
Aug 24 16:59:24 murdock pppd[29379]: Using interface ppp0
Aug 24 16:59:24 murdock pppd[29379]: Connect: ppp0 /dev/pts/3
Aug 24 16:59:55 murdock pppd[29379]: LCP: timeout sending Config-Requests
Aug 24 16:59:55 murdock pppd[29379]: Connection terminated.
Aug 24 16:59:55 murdock pppd[29379]: Modem hangup
Aug 24 16:59:59 murdock pppoe[29380]: Timeout waiting for PADO packets
Aug 24 16:59:59 murdock pppd[29379]: Exit.
Aug 24 16:59:59 murdock pppoe-connect[29409]: PPPoE connection lost; attempting re-connection.

I know to remove the C2100T, I need to use VLAN tagging 201, which I've located recipies online for that, but without the ppp authentication working I'm stuck.

Here are some of the configuration files /etc/chap-secrets

#Secrets for authentication using CHAP
# client        server  secret                  IP addresses

"[email protected]"      *       "password"

firewall ethernet cfg:

DEVICE=enp2s0f1
TYPE=Ethernet
BOOTPROTO=dhcp
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
NAME=p1p2
ONBOOT=yes
DNS1=127.0.0.1
DOMAIN=foddy.home
HWADDR=A0:36:9F:83:5E:61
DNS2=205.171.3.65
USERCTL=no
PROXY_METHOD=none
BROWSER_ONLY=no
IPV6_ADDR_GEN_MODE=stable-privacy

/etc/sysconfig/network-scripts/ifcfg-ppp0

USERCTL=no
BOOTPROTO=dialup
NAME=DSLppp0
TYPE=xDSL
ONBOOT=yes
PIDFILE=/var/run/pppoe-adsl.pid
FIREWALL=NONE
PING=.
PPPOE_TIMEOUT=80
LCP_FAILURE=3
LCP_INTERVAL=20
CLAMPMSS=1412
CONNECT_POLL=6
CONNECT_TIMEOUT=0
DEFROUTE=yes
SYNCHRONOUS=no
ETH=enp2s0f1
PROVIDER=DSLppp0
USER="[email protected]"
PEERDNS=no
DNS1=127.0.0.1
DNS2=205.171.3.65
DEMAND=no
IPV6INIT=no
IDLETIMEOUT=600
PERSIST=no

The firewall is run from Shorewall, I won't include those files here but I have no reason to believe they are involved.

Most of these files are essentially unchanged from when they ran fine in the DSL.

I really haven't been able to find any good diagnostic settings for the pppoe/pppd to give me verbose outputs to help debug things.

Does anyone have any guidance of what might be wrong or how to make progress?

Thanks Brian

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    just a random note: Aug 24 16:59:55 murdock pppd[29379]: LCP: timeout sending Config-Requests your box (or isp) seems to be unable to do config request "syncing" LCP is failing, so increase LCP debugging. some search first hit link: linuxquestions.org/questions/linux-networking-3/… i would go for understanding how LCP works, increasing debugging of the whole PPP connection from your part, and read through the logs until you find the error.
    – Dennis Nolte
    Aug 27, 2019 at 7:57
  • I found some debugging options, but unfortunately they really don't tell me anything except its sending packets out and getting nothing back.
    – bfoddy
    Aug 29, 2019 at 3:58
  • Is there a network tool that can sniff the packets sent from my modem? Something along the line of a custom linux distribution that I can plumb in between the modem and ONT to capture the negotiation. Its ethernet, not IP, so it needs to work on raw ethernet packets.
    – bfoddy
    Aug 29, 2019 at 16:31
  • wireshark/tshark should be able to intercept the data from your fedora box to the, as for in between: most likely possible but never done that sorry. you should have an /etc/ppp/options file where you can increase debug logging. i think it was kdebug 7 which gives you the most info you might be able to manually connect going the whole pppscript in a minicom terminal, eliminating an issue there already (which i am not sure might or might not work for you already) once you are certain the serial connection works correctly use something like this to get verbose output:
    – Dennis Nolte
    Aug 30, 2019 at 7:49
  • /usr/sbin/pppd mtu 1492 ipcp-accept-local ipcp-accept-remote connect "/usr/sbin/chat -v -f /etc/ppp/pppscript" for the authentication process. Additionally it might be helpful (for others) to add your options here.
    – Dennis Nolte
    Aug 30, 2019 at 7:49

2 Answers 2

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According to this all traffic has to have a 201 vlan tag: https://nickmooney.com/centurylink-fiber-bypass-modem/

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I tried to put the 201 vlan tag through the old /etc/sysconfig/network-... scripts several different ways, but nothing seemed to work (and gave up for many months, using the external modem and NAT). Finally I made another attempt using NetworkManager and it just worked. Previously, I've always resisted using NM for complicated configurations like this, but in this case it worked.

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