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This section introduces
tools for verifying and troubleshooting a PPP session. One
way to determine whether PAP or CHAP authentication was passed is to
use the show dialer command. This command must be used to
view the progress of asynchronous dialup connections.
If show dialer displays the
name of the remote router, it means that you passed PAP or CHAP
authentication, as shown in Figure .
You can check the show dialer
command on both routers to verify that the name of the other router
is displayed. If it is, then you know that PAP or CHAP
authentication is working.
If you do not see the name of the
other host, you know that something was misconfigured because the
authentication failed in at least one direction.
The debug ppp negotiation
command is a great tool for
troubleshooting the PPP LCP activities such as authentication,
compression, and multilink. When the LCP is in OPEN state, the NCP
negotiation takes place. In the following output, you can observe
that for PPP to work, LCP options must be negotiated before any NCP
activities take place. You therefore see the negotiations shown in
Figure :
- CHAP authentication;
- Compression Control Protocol (CCP);
- NCP protocols IP, IPX, and Cisco
Discovery Protocol (CDP).
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