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6-66

Configuring the Data Link Layer Protocol for E1, T1, and Serial Interfaces

Troubleshooting Logical Interfaces

Incompatible Authentication Protocols. If you do not receive any PPP

authentication debug messages at all, the local and remote routers may be

requesting different authentication protocols. In this case, the LCP state will

not come up because the peers cannot negotiate the authentication option.

You could test this theory by debugging PPP negotiation events and looking

for a Conf-Nak message. This message indicates that one of the peer’s must

refuse an option proposed by the other.

Caution PPP debug messages are processor intensive: peers exchange LCP frames

again and again in an attempt to negotiate the session. If the router is currently

supporting network traffic, debugs can compromise its functions. When you

suspect that authentication is keeping a connection from going up, you can

simply try changing the type of authentication you require or send. If the PPP

connection then goes up (or if PPP authentication debug messages appear),

you know that incompatible authentication protocols were at least partially

at fault.

In Figure 6-27, the local router requires PAP, but the remote router is config-

ured for CHAP.

Figure 6-27. Debugs for Incompatible Authentication Protocols

Troubleshooting the Frame Relay Interface

When you troubleshoot the Frame Relay connection, you should first check

the Frame Relay interface and then check the Frame Relay subinterface. From

the enable mode context, enter the following command to check the status of

a Frame Relay interface that is bound to the E1, T1, or serial interface:

Syntax: show interface frame-relay <number>

ProCurve# debug ppp negotiation

2005.07.08 09:11:12 PPP.NEGOTIATION PPPrx[t1 1/1] LCP: Conf-Req ID=74

Len=20 ACCM(00000000) AP(PAP)MAGIC(da5bf7de)

2005.07.08 09:11:12 PPP.NEGOTIATION PPPtx[t1 1/1] LCP: Conf-Nak D=74

Len=9 AP(CHAP)

Peer requires PAP

Peer requests PAP, but the

local router requires CHAP

Message from the peer

HP ProCurve 7000dl Series User Manual

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