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Troubleshooting PADI timeout issue

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Article ID: KB14951 KB Last Updated: 30 Sep 2011Version: 3.0
Summary:
Unable connect to Internet using new DSL connectivity.  The event log shows PADI timeout error.
Symptoms:
PADI Means PPPoE Active Discovery Initiation. It is the first step in the PPPoE establishment protocol.

The protocol negotiates in the following order:

NetScreen device --------------------PADI----------------> Access Concentrator/PPPoE Server
                 <-------------------PADO-----------------
                ---------------------PADR--------------->
                 <-------------------PADS-----------------


PADI: PPPoE active discovery initiation from client to request a service from any PPPoE servers.

While connecting to a PPPoE connection if it fails and event log shows as PADI time out, then it could be because the NetScreen device sent the PADI however there is no response from the ISP and finally PADI times out.

Solution:
The first thing to check is the event log output with the command 'get log event':
2008-06-14 11:30:12 system notif 00537 Point-to-Point Protocol over Ethernet
(PPPoE) connection failed to establish
a session. Timeout PADI

2008-06-14 11:30:03 system notif 00537 PPPoE session started negotiations.
Meaning : PADI (which is PPPoE active discovery initiation from client to request a service from any PPPoE servers) sent by the firewall to the BRAS at ISP is being rejected. In working condition, firewall receives PADO in response.

For these errors, confirm the following with the ISP:
  1. PVC value (which specifies the VPI and VCI numbers for an ADSL interface) should match with the ISP. Valid VPI range is 0-255, default is 8. Valid VCI range is 32-65535, default is 35.

  2. MUX (encapsulating method for carrying network traffic for an ADSL interface. The default mux is LLC).

  3. Whether the PADI reached the BRAS and the reason for it being discarded. 

  4. Physical operating-mode for the ADSL interface. The options available are auto, ansi-dmt, glite, itu-dmt, adsl2, adsl2plus, adsl2plus-annexM. If the customer is not aware of which option to select and the ISP also is not co-operating, then set it to “auto” so that it automatically negotiates with the DSLAM. But exact information would be helpful.

  5. qos (if configured) - Sets the ATM QoS type. The QOS keyword options are as follows:

  6. cbr specifies the CBR service class
    ubr specifies the UBR service class
    vbr-nrt specifies the VBR-NRT service class

  7. Protocol - Sets the protocol type for an ADSL interface. Typically, most ISP use 1483briged mode for PPPoE.

  8. The following "debug pppoe all" output confirms that we are sending PADI but not recieving PADO

    ## 2008-06-14 11:39:22 : send_padi: about to send PADI to i/f adsl1/0, num_attemps 2
    ## 2008-06-14 11:39:22 : Including tag SERVICE(len=0)
    Including tag UNIQ(len=4), value:00.00.08.40
    PPPoE Send:adsl1/0: Des MAC:ff.ff.ff.ff.ff.ff,Src MAC:00.1b.c0.3a.d5.98,Ether Type: 8863
    Ver/Type=11,Code=PADI,Sid=0,Len=c
    Tag=SERVICE,Len=0;Tag=UNIQ,Len=4,Value=00.00.08.40;
    ## 2008-06-14 11:39:22 : send_discovery_pak: pass the packet to netif out i/f adsl1/0
    ## 2008-06-14 11:39:25 : PADI/PADR timeout after 3 retries, context adsl1/0
    ## 2008-06-14 11:39:25 : pppoe_fsm_reset dns_handle = 0
    ## 2008-06-14 11:39:25 : pppoe_fsm_reset clear ip wrong
    ## 2008-06-14 11:39:25 : pppoe_session_shutdown(Inst:adsl1/0, from 0): auto con enabled and first auto con not done yet

Additional Info regarding PADI negotiations:

DEFINITIONS:
PADO: PPPoE active discovery offer from PPPoE servers replying to the client.
PADR: PPPoE active discovery request from client to one particular PPPoE server.
PADS: PPPoE active discovery session-confirmation from server agreeing to bring up the next phase.

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