Introduction
I will be summarizing the troubleshooting method for PPPoE connection failure using the specific connection failure examples and debug logs. I will post this topic in several articles.
1. Checking the Connection Status
As a first step, you will need to check if the PPPoE session connection has been established successfully. You will use the following command output to check the connection.
* This is the result obtained by a router operated as the PPPoE client using IOS 15.0M.
PPPoE_Client# show ppp all
Interface/ID OPEN+ Nego* Fail- Stage Peer Address Peer Name
------------ --------------------- -------- --------------- --------------------
PPPoE_Client#
PPPoE_Client# show pppoe session
1 client session
Uniq ID PPPoE RemMAC Port VT VA State
SID LocMAC VA-st Type
N/A 0 0000.0000.0000 Et0/0 Di1 N/A SHUTDOWN
0000.0000.0000
* Nothing appears because it is not connected.
PPPoE_Client# show ppp all
Interface/ID OPEN+ Nego* Fail- Stage Peer Address Peer Name
------------ --------------------- -------- --------------- --------------------
Vi2 LCP+ IPCP+ CDPCP- LocalT 192.168.1.1 PPPoE_Serv
PPPoE_Client#
PPPoE_Client# show pppoe session
1 client session
Uniq ID PPPoE RemMAC Port VT VA State
SID LocMAC VA-st Type
N/A 2 aabb.cc00.d300 Et0/0 Di1 Vi2 UP
aabb.cc00.d400 UP
* The sessions for both PPPoE and PPP are displayed.
2. Troubleshooting for Connection Failure
Incorrect settings are often the cause of issues where the connection was not established within the installation schedule when trying to establish the connection.
The following are typical examples.
- Incorrect router settings for the IP address assignment (auto/fixed)
- Incorrect password settings
- Authentication method negotiation failure
- MTU negotiation failure
For "1. Incorrect router settings for the IP address assignment (auto/fixed)," troubleshoot the problem using the CCO document as reference. For the other problems, it could be an issue that depends on the destination equipment or it is difficult to determine where and what to fix by looking at show running-config. Please obtain debug logs by enabling debugging. You can identify the cause of the connection failure by checking the results of debug logs.
The debug logs you are recommended to obtain in the first step are as follows:
debug ppp authentication
debug ppp negotiation
debug pppoe event
The CCO document introduces the detailed description of how to check the obtained debug logs. Please see the CCO document as well.
Understanding debug ppp negotiation Output
http://www.cisco.com/c/en/us/support/docs/wan/point-to-point-protocol-ppp/25440-debug-ppp-negotiation.html
Related Information
Original Document: https://supportforums.cisco.com/ja/document/92886
Author: Katsunori Ishizuka
Posted on February 23, 2012
Troubleshooting for PPPoE Connection Failure - Part 2 -
Troubleshooting for PPPoE Connection Failure - Part 3 -
