Troubleshooting PPP links

Perform PAP or CHAP authentication

In this example, neither host chose to authenticate the other using PAP or CHAP. Only login authentication was performed when the connection was initiated.

60  Link link_0 : Phase was ESTABLISH, Phase Now AUTHENTICATE
61  Link link_0 : Authentication Initialized
62  Link link_0 : CHAP Started
63  Link link_0 : PAP Started
64  Link link_0 : Authentication Complete
65  Link link_0 : CHAP Terminated
66  Link link_0 : PAP Terminated

If the remote side refused to authenticate itself using the protocol (PAP or CHAP) requested by the local side, negotiation would fail and the connection would already have been dropped during the LCP phase. See ``Negotiate LCP parameters'' for more information.

If the remote side authenticates the local side using PAP, you should see messages such as the following if it succeeds:

   PAP Sending Request. Name 'foo', Secret 'clydenw'
   PAP Message 'Authentication successful'
   PAP Authentication with Peer Succeeded

If the local side authenticates the remote side using PAP, you should see messages such as the following if it succeeds:

   Authentication Initialised (timeout 60 seconds)
   PAP Started
   PAP Received Request
   PAP Name 'foo', Secret 'clydenw'
   PAP Peer succeeded PAP authentication (Send Ack)

If the remote side authenticates the local side using CHAP, you should see messages such as the following if it succeeds:

   CHAP Received Challenge
   CHAP Peer Name 'barsoom'
   CHAP Sending response. Local name 'foo'
   CHAP Received SUCCESS
   CHAP Message 'Authentication successful'
   CHAP Authentication with Peer Succeeded

If the local side authenticates the remote side using CHAP, you should see messages such as the following if it succeeds:

   Authentication Initialised (timeout 60 seconds)
   CHAP Started
   CHAP Send Challenge. Name 'barsoom'
   PAP Started
   ...
   CHAP Received Response
   CHAP Peer Name 'foo'
   CHAP Received Valid Response (Send Success)
   Authentication -  Peer name is 'foo'
   Authentication Complete

The following sections detail cases where authentication might fail:

For more information about PAP and CHAP authentication, see pppauth(7).

Secret not found in the authentication database

Authentication will fail and you will see one of the following warnings if the authentication database is configured incorrectly:

   PAP WARNING No secret for the name peername
   CHAP WARNING No secret for the name peername

The protocol will be shown as PAP or CHAP depending on the type of authentication being performed. The possible causes of such warnings are:

The local host (the peer) failed to be authenticated by the remote host because a peer secret had not been defined for the peername and the protocol in the local authentication database.
The local host failed to authenticate the remote host (the peer) because a local secret had not been defined for the peername and the protocol in the local authentication database.

Local host fails to be authenticated by remote host using PAP

If the local host failed to authenticate itself with the remote host using PAP, you would expect to see messages such as the following before the connection was closed:

   PAP Sending Request. Name 'foo', Secret 'clydenw'
   PAP Received Nak
   PAP Message 'Authentication failed'
   PAP Failed to authenticate with Peer

This may be because the local host gave the wrong password, or the remote host's authentication database did not contain a local PAP secret for the peer.

Local host fails to authenticate remote host using PAP

If the local host failed to authenticate the remote host (the peer) using PAP because the remote host gave the wrong password, you would expect to see messages such as the following before the connection was closed:

   PAP Received Request
   PAP Name 'foo', Secret 'clydenw'
   PAP Peer failed PAP authentication (Send Nak)

Local host fails to be authenticated by remote host using CHAP

If the local host failed to authenticate itself with the remote host using CHAP, you would expect to see messages such as the following before the connection was closed:

   CHAP Received Challenge
   CHAP Peer Name 'barsoom.acme.com'
   CHAP Sending response. Local Name 'foo'
   CHAP Message 'Authentication failed'
   CHAP Failed to authenticate with Peer

This may be because the local host sent an incorrect response value calculated from an invalid secret, or the remote host's authentication database did not contain a local CHAP secret for the peer.

Local host fails to authenticate remote host using CHAP

If the local host failed to authenticate the remote host (the peer) using CHAP because the remote host sent an incorrect response value calculated from an invalid secret, you would expect to see messages such as the following before the connection was closed:

   CHAP Send Challenge. Name 'barsoom.acme.com'
   CHAP Received Response
   CHAP Peer Name 'foo'
   CHAP Received invalid Response (Send Fail)