Troubleshooting guide

*Mar 1 04:52:43.418: Vi1 LCP: I CONFREQ [ACKrcvd] id 182 Len 14
*Mar 1 04:52:43.418: Vi1 LCP: AuthProto PAP (0x0304C023)
*Mar 1 04:52:43.418: Vi1 LCP: MagicNumber 0x39D50E9B (0x050639D50E9B)
Router#undebug all
Whether its an I or an O packet, a Configure−Negative−Acknowledge (CONFNAK) is indicative of a PPP
configuration mismatch. What this means is that one side of the PPP connection is asking for a PPP option
that the other side is unable or not configured to perform. If the Cisco DSL Router is sending the CONFNAK
(indicated by "O CONFNAK"), the Cisco DSL Router is not able to perform or not configured for the option
the ISP is sending. If the CONFNAK is being sent by your ISP (indicated by "I CONFNAK"), you have
configured an option on the Cisco DSL Router that your ISP is not willing to perform.
The line following the CONFNAK describes the option that is being rejected. In this example output, the
option is Challenge Handshake Authentication Protocol (CHAP) but it could be any option. The only place on
the Cisco DSL Router where PPP options can be configured is interface dialer 1. Issue the command show
run interface dialer 1 to view your interface dialer 1 configuration.
If your ISP is sending the I CONFNAK, look for commands under interface dialer 1 that match the line
following the CONFNAK and remove them. If the Cisco DSL Router is sending the O CONFNAK, add a
command to interface dialer 1 to properly negotiate PPP with your ISP. In the case of the router sending
packets, you may need to call the Cisco TAC to determine which command(s) need to be enabled on the Cisco
DSL Router.
Authentication Failure
An authentication failure occurs when your ISP is unable to authenticate your PPP username or password.
There are two scenarios in which this may occur. The first scenario is an authentication type mismatch, which
is caused when you don't properly configure the router. All the authentication configurations listed in this
document account for both Password Authentication Protocol (PAP) and CHAP authentication types. For
configuration flexibility, you should have both CHAP and PAP configured. If you don't have both configured,
you may see output from a debug ppp command like the following:
Router#debug ppp negotiation
00:34:29: Vi1 LCP:OCONFREQ [REQsent] id 53 Len 15
00:34:29: Vi1 LCP: AuthProto CHAP (0x0305C22305)
!−−− Sending CHAP requests.
00:34:29: Vi1 LCP: MagicNumber 0x01B63483 (0x050601B63483)
00:34:29: Vi1 LCP: I CONFREQ [REQsent] id 252 Len 14
00:34:29: Vi1 LCP: AuthProto PAP (0x0304C023)
!−−− Receiving PAP requests from the service provider.
00:34:29: Vi1 LCP: MagicNumber 0xBC5233F9 (0x0506BC5233F9)
00:34:29: Vi1 LCP: O CONFREJ [REQsent] id 252 Len 8
Router#undebug all
or
Router# debug ppp negotiation
00:45:44: Vi1 LCP: I CONFREQ [Listen] id 141 Len 15
00:45:44: Vi1 LCP: AuthProto CHAP (0x0305C22305)
!−−− Receiving CHAP requests from the service provider.
00:45:44: Vi1 LCP: MagicNumber 0xBC5C7DDC (0x0506BC5C7DDC)
00:45:44: Vi1 LCP: O CONFREQ [Listen] id 255 Len 14
00:45:44: Vi1 LCP: AuthProto PAP (0x0304C023)
!−−− Sending out PAP requests.
Router#undebug all
!−−− Turn off ppp debug.
Cisco DSL Router Configuration and Troubleshooting Guide