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[Mick]

At 2 in the morning my logs tell me that my router lost its PPPoE authenticated session, on a 20CN service.  Rebooting the router, changing its firmware, replacing the bridged modem brought no PPP session up.

The modem syncs with the exchange and gets a good speed.  I even tried using an old Netgear router, configured for PPPoE and still no session is established.

Then I did away with the router and bridged modem and connected the Netgear configured for PPPoA.  It established a PPP session immediately.

Looking at the ISP's control panel for my service I noticed that instead of being connected to Ealing RAS, as I have been for as long as I care to remember, my connection had been moved to Milton Keynes.  This may be a coincidence, but could it be that the Milton Keynes RAS servers do not detect accurately a PPPoE packet and only work with PPPoA?  If so how could I go about finding if this is a BT policy, or some RAS software bug?

[kitz]

BTw have been busy over the past few weeks remapping their routing from the RASes and 21CN core nodes, which is likely why you will have noticed the change fairly recently.

As far as Im aware for >10yrs BTw have used PPPoEoA to emulate PPPoE on their ATM 20CN backhaul so why it should suddenly stop working now Im unsure.  I would think that your ISP probably has the best means to take this up with BTw.

[Mick]

Thank you kitz,

I've taken it up with my ISP.  I'll wait to hear what they come back with.

Until then I'll set up PPPoE on my laptop and capture some packets to see what's going on.  When I looked at the logs of the router there was nothing informative there - as if the RAS did not respond at all.

[kitz]

Good luck and please do keep me informed as I will be interested in what they have to say

[Mick]

I had some time today and experimented both with a 2Wire 2700HGV and a Netgear DG834 in bridged mode.  I tried both my normal ISP username and passwd and the "speedtest_user@speedtest_domain" login using my router's PPPoE client, then my laptop's PPPoE client (linux), then a MSWindows XP MiniPort PPPoE.  All three failed to get response with each modem, when in the past I had no such problem.

It seems to me that the Milton Keynes RAS does not return anything to my PPPoE packets.  Taking each client in turn this is what I have seen.

1. Router Status (an american Cisco-like device):

Code: [Select]

Status for "ppp 1"
Port Status
Connected Interface eth 0/1
Link State INITIAL
LCP State Negotiating
IP Address 0.0.0.0
Peer IP Address 0.0.0.0
Primary DNS Server 0.0.0.0
Secondary DNS Server 0.0.0.0
Queueing method fifo
HDLC tx ring limit 0
Output queue
(size/highest/max total/drops) 0/0/200/0
2. Router PPPoE client log:

Code: [Select]

2014.10.02 04:50:43 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43108
2014.10.02 04:50:48 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43109
2014.10.02 04:50:53 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec4310a
2014.10.02 04:50:58 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec4310b
2014.10.02 04:51:03 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec4310c
2014.10.02 04:51:08 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec4310d
2014.10.02 04:51:13 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec4310e
2014.10.02 04:51:18 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec4310f
2014.10.02 04:51:24 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43110
2014.10.02 04:51:29 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43111
2014.10.02 04:51:34 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43112
2014.10.02 04:51:39 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43113
2014.10.02 04:51:44 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43114
2014.10.02 04:51:49 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43115
2014.10.02 04:52:39 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43116
2014.10.02 04:52:44 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43117
2014.10.02 04:52:49 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43118
2014.10.02 04:52:54 PPPOE.CLIENT Sending PADI Message: Xid = 0xaec43119
As you can see above the router is sending 'PPPoE Active Discovery Initiation' packets, but there is no response from the RAS end.


3. Laptop PPPoE client config:

Code: [Select]

#PPPoE configuration
config_enp11s0=null
config_ppp0="ppp"
link_ppp0="enp11s0"
plugins_ppp0="pppoe"
username_ppp0='my_ISP_username'
password_ppp0='**********'
pppd_ppp0="
noauth
defaultroute
usepeerdns
holdoff 3
child-timeout 60
lcp-echo-interval 15
lcp-echo-failure 3
debug
noaccomp noccp nobsdcomp nodeflate nopcomp novj novjccomp"
#
rc_net_need_ppp0="net.enp11s0"
4. PC PPPoE client log:

Code: [Select]

Oct  4 14:10:15 dell_xps pppd[27881]: RP-PPPoE plugin version 3.8p compiled against pppd 2.4.7
Oct  4 14:10:15  pppd[27881]: Plugin passwordfd.so loaded.
Oct  4 14:10:15  pppd[27882]: pppd 2.4.7 started by michael, uid 0
Oct  4 14:10:15  pppd[27882]: Send PPPOE Discovery V1T1 PADI session 0x0 length 12
Oct  4 14:10:15  pppd[27882]:  dst ff:ff:ff:ff:ff:ff  src 00:26:b9:20:b4:9c
Oct  4 14:10:15  pppd[27882]:  [service-name] [host-uniq  ea 6c 00 00]
Oct  4 14:10:15  /etc/init.d/net.ppp0[27753]: WARNING: net.ppp0 has started, but is inactive
Oct  4 14:10:17  kernel: tg3 0000:0b:00.0 enp11s0: Link is up at 100 Mbps, full duplex
Oct  4 14:10:17  kernel: tg3 0000:0b:00.0 enp11s0: Flow control is off for TX and off for RX
Oct  4 14:10:17  kernel: IPv6: ADDRCONF(NETDEV_CHANGE): enp11s0: link becomes ready
Oct  4 14:10:20  pppd[27882]: Send PPPOE Discovery V1T1 PADI session 0x0 length 12
Oct  4 14:10:20  pppd[27882]:  dst ff:ff:ff:ff:ff:ff  src 00:26:b9:20:b4:9c
Oct  4 14:10:20  pppd[27882]:  [service-name] [host-uniq  ea 6c 00 00]
Oct  4 14:10:30  pppd[27882]: Send PPPOE Discovery V1T1 PADI session 0x0 length 12
Oct  4 14:10:30  pppd[27882]:  dst ff:ff:ff:ff:ff:ff  src 00:26:b9:20:b4:9c
Oct  4 14:10:30  pppd[27882]:  [service-name] [host-uniq  ea 6c 00 00]
Oct  4 14:10:50  pppd[27882]: Timeout waiting for PADO packets
Oct  4 14:10:50  pppd[27882]: Unable to complete PPPoE Discovery
Oct  4 14:10:53  pppd[27882]: Send PPPOE Discovery V1T1 PADI session 0x0 length 12
Oct  4 14:10:53  pppd[27882]:  dst ff:ff:ff:ff:ff:ff  src 00:26:b9:20:b4:9c
Oct  4 14:10:53  pppd[27882]:  [service-name] [host-uniq  ea 6c 00 00]
Oct  4 14:10:58  pppd[27882]: Send PPPOE Discovery V1T1 PADI session 0x0 length 12
Oct  4 14:10:58  pppd[27882]:  dst ff:ff:ff:ff:ff:ff  src 00:26:b9:20:b4:9c
Oct  4 14:10:58  pppd[27882]:  [service-name] [host-uniq  ea 6c 00 00]
Oct  4 14:11:08  pppd[27882]: Send PPPOE Discovery V1T1 PADI session 0x0 length 12
Oct  4 14:11:08  pppd[27882]:  dst ff:ff:ff:ff:ff:ff  src 00:26:b9:20:b4:9c
Oct  4 14:11:08  pppd[27882]:  [service-name] [host-uniq  ea 6c 00 00]
Oct  4 14:11:28  pppd[27882]: Timeout waiting for PADO packets
Oct  4 14:11:28  pppd[27882]: Unable to complete PPPoE Discovery
5. tcpdump capture from laptop:

Code: [Select]

14:24:07.931635 00:26:b9:20:b4:9c (oui Unknown) > Broadcast, ethertype PPPoE D (0x8863), length 32: PPPoE PADI [Service-Name] [Host-Uniq 0x2C710000]
0x0000:  ffff ffff ffff 0026 b920 b49c 8863 1109  .......&.....c..
0x0010:  0000 000c 0101 0000 0103 0004 2c71 0000  ............,q..
14:24:12.956866 00:26:b9:20:b4:9c (oui Unknown) > Broadcast, ethertype PPPoE D (0x8863), length 32: PPPoE PADI [Service-Name] [Host-Uniq 0x2C710000]
0x0000:  ffff ffff ffff 0026 b920 b49c 8863 1109  .......&.....c..
0x0010:  0000 000c 0101 0000 0103 0004 2c71 0000  ............,q..
14:24:14.828566 00:a0:c8:2a:13:68 (oui Unknown) > Broadcast, ethertype Unknown (0x9999), length 60:
0x0000:  ffff ffff ffff 00a0 c82a 1368 9999 002a  .........*.h...*
0x0010:  0c0c 0000 0000 0002 0004 0003 0004 00e7  ................
0x0020:  0004 10ed 0004 20ed 0004 00e6 0004 00ff  ................
0x0030:  0004 1010 0004 2010 0004 ffff            ............
14:24:22.989121 00:26:b9:20:b4:9c (oui Unknown) > Broadcast, ethertype PPPoE D (0x8863), length 32: PPPoE PADI [Service-Name] [Host-Uniq 0x2C710000]
0x0000:  ffff ffff ffff 0026 b920 b49c 8863 1109  .......&.....c..
0x0010:  0000 000c 0101 0000 0103 0004 2c71 0000  ............,q..
14:24:44.892089 00:a0:c8:2a:13:68 (oui Unknown) > Broadcast, ethertype Unknown (0x9999), length 60:
0x0000:  ffff ffff ffff 00a0 c82a 1368 9999 002a  .........*.h...*
0x0010:  0c0c 0000 0000 0002 0004 0003 0004 00e7  ................
0x0020:  0004 10ed 0004 20ed 0004 00e6 0004 00ff  ................
0x0030:  0004 1010 0004 2010 0004 ffff            ............
14:24:46.120620 00:26:b9:20:b4:9c (oui Unknown) > Broadcast, ethertype PPPoE D (0x8863), length 32: PPPoE PADI [Service-Name] [Host-Uniq 0x2C710000]
0x0000:  ffff ffff ffff 0026 b920 b49c 8863 1109  .......&.....c..
0x0010:  0000 000c 0101 0000 0103 0004 2c71 0000  ............,q..
14:24:51.145853 00:26:b9:20:b4:9c (oui Unknown) > Broadcast, ethertype PPPoE D (0x8863), length 32: PPPoE PADI [Service-Name] [Host-Uniq 0x2C710000]
0x0000:  ffff ffff ffff 0026 b920 b49c 8863 1109  .......&.....c..
0x0010:  0000 000c 0101 0000 0103 0004 2c71 0000  ............,q..
14:25:01.196081 00:26:b9:20:b4:9c (oui Unknown) > Broadcast, ethertype PPPoE D (0x8863), length 32: PPPoE PADI [Service-Name] [Host-Uniq 0x2C710000]
0x0000:  ffff ffff ffff 0026 b920 b49c 8863 1109  .......&.....c..
0x0010:  0000 000c 0101 0000 0103 0004 2c71 0000  ............,q..

6. MSWindows Error:

Code: [Select]

Connecting through WAN MiniPort (PPPOE) ...

Error 678: The remote computer did not respond.
I am guessing that the PPPoA enapsulation that the modems perform in bridged mode are not liked by the RAS RADIUS in Milton Keynes.  Since I had no such problem when connected to Ealing I am guessing again that this is a RAS problem, rather than something to do with my equipment.

As soon as I set up the modem as a router and configure it to use PPPoA it immediately connects to the RAS/ISP and I can get to the Internet.

I really need to use my router for VLANs, trunking, VPNs and other functionality that the 2Wire and Netgear do not offer.  Is there anything that I could say to my ISP to help them take this up with BT?

[Mick]

My ISP advised that if my bridged modem set up stopped working following a PEW by BT, I would need to change the ATM encapsulation from VC-MUX to LLC.

Indeed, after I changed the modem's ATM setting to LLC the router was able to establish a PPPoE session without any further ado.   

My local exchange is still on 20CN.  I left the circuit identifiers as VPI:0 and VCI:38, which is what I always had under VC-MUX.  From what I figured following the engineering works the LLC encap. is only necessary when using PPPoE with bridged ATM.  When I configured the Netgear to use PPPoA, VC-MUX had no problem establishing a session.  I still don't know why this change was necessary, but would welcome any explanation (for my education).

Just to throw in a possible red herring, I also tried setting up a 2Wire to perform PPPoA with VC-MUX and it failed to authenticate.  Perplexed . . .

EDIT:  Just found this notice:  http://www.sinet.bt.com/sinet/sins/pdf/482v1p13.pdf 
It seems that PPPoE is only supported over LLC since last year.  I guess it was a matter of time before it caught up with me.  Ealing RAS must have had an old  configuration, while Milton Keynes more modern kit that ignored my PADI packets.  If anyone has a more informed explanation I'd be interested to know.