topic Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem in Broadband

Configuring OpenWRT for PPPoE via Openreach FTTC modem

jimbof — Thu, 02 May 2013 05:41:40 GMT

So my FTTC fibre install has gone ahead and is now working. I'd ideally like to not use the plusnet router and use my OpenWRT router over PPPoE. This was working fine with my old provider (TalkTalk LLU) using a cheap TPLINK ADSL modem in PPPoE mode, but with the BT Openreach modem connected I get the following PPPoE error in the connection logs:
"May 2 05:31:20 OpenWrt daemon.warn pppd[2739]: Timeout waiting for PADO packets
May 2 05:31:20 OpenWrt daemon.err pppd[2739]: Unable to complete PPPoE Discovery"
Anyone have this kind of setup working?

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

pwatson — Thu, 02 May 2013 07:16:24 GMT

I'm running Gargoyle on my router and find that it takes around 5 mins to connect. I haven't looked at the log to find out why but looking on Google suggests your issue may be related.
How long do you leave the router to connect?

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

MisterW — Thu, 02 May 2013 07:18:56 GMT

Other people have seen similar problems with other routers http://community.plus.net/forum/index.php/topic,108935.0.html . I'm not sure that anyone has really got to the bootom of the problem though. It just seems that leave it alone and it eventually connects is the answer...

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

jimbof — Thu, 02 May 2013 09:04:47 GMT

Thanks for the pointers; I'll give it a go and have a play, see if there are any options that are useful.
I think an additional complication is that my OpenWRT box is a fast x86 small form factor PC with 3 gigabit interfaces; openWRT actually cycles the WAN interface up and down each time it gets one of these timeouts - to the extent of the "happy light" for the ethernet port turning on and off. If I find an answer I'll let you all know

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

MisterW — Thu, 02 May 2013 10:02:26 GMT

I've just been having a bit of a look around and come across a couple of posts indicating that Service Name may be an issue with pppoe discovery.
This one https://forum.openwrt.org/viewtopic.php?id=29821 regarding setting it on OpenWrt.
This one http://community.plus.net/forum/index.php/topic,88204.32.html which seems to indicate it should be set to 'Plusnet' and one on the A & A Site
which seems to indicate it should be blank

Quote
Note that FTTC works differently to typical ADSL broadband and includes a BT VDSL router which talks PPPoE. You will need PPPoE equipment or software to use the service. A PPPoE router can be used. The PPPoE service name must be left blank.

Might be worth checking what is configured for Service Name in your OpenWrt and maybe experimenting with either Plusnet or blank.

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

jimbof — Thu, 02 May 2013 10:22:55 GMT

Conflicting indeed. I just logged into the web interface on the Thomson which is up at the moment and I can see there doesn't seem to be a service name in place:
"Service Name: -"
It won't hurt to try though. I see the posts are quite old though so perhaps it is no longer necessary.
The other thought I had was whether the modem needs power cycling if you change the router that is connected to it. In my case so far I hadn't - just swapped the ethernet between the Thomson and the OpenWRT box. I would expect that to be enough to reset the modem, but perhaps it isn't.

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

MisterW — Thu, 02 May 2013 10:40:13 GMT

Quote
The other thought I had was whether the modem needs power cycling if you change the router that is connected to it.

I wouldn't have expected the modem to need power cycling when changing the router. What IS probably a good idea is to manually disconnect the pppoe session on the router before unplugging, that way at least you know that there is no active ppp session that needs to timeout before the new router can connect.

Quote
I can see there doesn't seem to be a service name in place:
"Service Name: -"

That tends to agree with the AA post, be interesting to see if OpenWrt has a different default.

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

jimbof — Thu, 02 May 2013 11:02:02 GMT

Default in OpenWRT is no service name, though you have the option to enter one, and also the concentrator name. I see the Thomson lists a concentrator in the info section, but by the looks of it it has been provided automatically down the line.
I didn't disconnect the session in the Thomson router first, and I was pushed for time so I didn't hang around much this morning. After seeing it not get connected I immediately swapped back to the Thomson. I wonder how long the server side PPP connections take to time out?

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

njay — Thu, 02 May 2013 12:39:48 GMT

I dont know if its relevant but extract from SIN495
Unlike other WBC access technologies, WBC FTTC accesses use the PPP (“Point-to-Point
Protocol”) session establishment to inform the BT Wholesale BRAS of the Openreach line
rate. It is therefore essential that the PPP session is re-started every time the VDSL line retrains.
To ensure this, the PPP / L2TP timeout values must be set to less than 20 seconds.

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

jimbof — Thu, 02 May 2013 13:13:28 GMT

Thanks, interesting. Well I'm sure I'll have some "fun" this evening!
How much of a problem for my throughput is fiddling with the connection going to be - is the line management going to peg me at some very low speed only to never rise again?

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

MisterW — Thu, 02 May 2013 13:17:25 GMT

As long as the modem isn't reset then it shouldn't really have any effect. Although I suppose that if the BRAS is aware of ppp session establishment then, even though the line rate isn't changing, it may take some ( but who knows what ? ) action...

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

bill888 — Thu, 02 May 2013 13:33:16 GMT

fwiw, I've encountered something very similar when I was testing PPPoE on ADSL and fibre.
As MisterW has already suggested, try just leaving your OpenWRT router for between 5 to 8 minutes to see if it would eventually establish the PPPoE connection.
I have been swapping between different ADSL/fibre modems and routers and encountered this timeout issue. PAD0 and 'ethernet concentrator cannot be reached' are some of the messages I've observed in the various logs. When using the fibre PN router, it can take 5-8 minutes before the Internet LED comes on after changing the BTOR modem.
I did try disconnecting the PPP session on one occasion on the TG582N, but it also seemed to cause the router to forget the password and I had to type it in again after rebooting the router. I haven't tried 'disconnecting' again when swapping modems.

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

MisterW — Thu, 02 May 2013 14:04:37 GMT

If there's nothing obvious from any of the tests so far suggested then it looks like OpenWrt might be able to give better diagnostics than commercial routers.
Setting pppd into verbose mode as indicated here http://wiki.openwrt.org/doc/howto/log.messages might give us more information to go on.

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

jimbof — Thu, 02 May 2013 14:17:51 GMT

I'll enable verbose mode before I start playing tonight.

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

jimbof — Thu, 02 May 2013 18:36:18 GMT

Ok so am now typing via my OpenWRT box.
Steps I took:
Enable PPPD logging.
Disconnect the Thomson router from web interface.
Power down Thomson router.
Power down OpenWRT box.
Power down Openreach modem.
Connect OpenWRT box to Openreach modem.
Wait 15 minutes.
Power on Openreach modem.
Wait for DSL light to solid green on Openreach modem.
Boot OpenWRT box.
Connected first time, instantly, without interaction.
Perhaps it is as simple as if there is an open session it takes a long time to die of it's own accord, and until then you get no reply to PADI with PADO?
Anyhow, will monitor to see if it is robust.

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

jimbof — Thu, 02 May 2013 19:48:27 GMT

Ok, so a reboot of the OpenWRT box results in a 6 minute wait for the PPPoE connection to finally kick in.
I see the logs of the PPPoE PADI being sent (3 times), with no reply coming back, then it takes down the interface and brings it back up to try again. Eventually it kicks in.
If I take down the PPPoE interface cleanly from the OpenWRT web UI, and then bring it back up from the webUI, the PPPoE connection is established within 10 seconds. This seems solid and repeatable.

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

jimbof — Thu, 02 May 2013 20:10:22 GMT

I can see that OpenWRT issues "ifdown -a" when the network is shut down (due to issuing a controlled router shutdown / restart). I imagine what might be happening is that "ifdown -a" goes through the list of network interfaces and shuts them all down one by one. But it gets to the ethernet interface that the PPPoE session is on before it shuts down the pppoe-wan interface (or perhaps it would never bother to try), and so the net result is that the ethernet transport is pulled from under the feet of the PPPoE session, just like if the router had been hard powered-off.
I've just simulated this by doing "ifconfig eth2 down" - which takes down the interface that I've got the openreach modem - and then doing "ifconfig eth2 up". The result of that is the long wait for it to eventually connect.
I guess a sticking plaster might be to fix up the shutdown scripts so that the pppoe-wan connection is taken down cleanly first. That would only fix scenarios where the router had been powered off / rebooted cleanly. It does seem a bit weird that these broken sessions hang around for quite so long.

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

MisterW — Fri, 03 May 2013 07:33:33 GMT

Good work there jimbof. As njay said earlier you would have expected the ppp timeout to be quite short ( < time taken for the VDSL resync ) and so it would be well and truly timedout before the 3 PADI requests have been and gone. Interesting results from the ifdown/up though, I wonder if the shutdown of the network interface is somehow ( not sure how though! ) is affecting the BT modem. The ASUS routers that seem to have been giving problems also have GPL code so it's quite possible that they use a significant amount of the same code as OpenWrt, may explain why they exhibit similar issues. We could really do with someone from PlusNet networks team to help with a controlled test and provide details of the ppp session timing so we can get to the bottom of this problem. There may not be much desire for that at the moment, since it works fine with the PlusNet TG582, but with self install for Fibre being on the horizon there's going to be more people out there using there own routers I would guess.

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

jimbof — Fri, 03 May 2013 08:49:17 GMT

I'm not sure it does work fine with the Thomson router - if you hard power cycle the Thomson router I think you see the same long connect time? But you can't get to any log files to see if there are connect errors, plus the Thomson is quite slow to boot anyhow.
I found with my OpenWRT box yesterday that if I disconnect the PPPoE connection and then reboot the OpenWRT box it connects instantly after the reboot.
Agree this really needs someone with access t the appropriate logs at Plusnet to help debug.
I could see a few interesting avenues for investigation:
1) make sure that OpenWRT is as good as it can be - ie take down the connection cleanly wherever possible
2) (not sure if this is feasible) Before making a PPPoE connection, attempt to kill any open session by sending the same thing down the wire that gets sent on a clean disconnection
But really, it seems like the problem is at the Plusnet PPP end.
Can anyone tell me - does the PPP session terminate at the cabinet, at the exchange, or at a Plusnet office somewhere?

Re: Configuring OpenWRT for PPPoE via Openreach FTTC modem

MisterW — Fri, 03 May 2013 08:53:58 GMT

I would have thought the ppp session must terminate at one of the PlusNet gateways.