You can use the ID ?¬?eld to associate a response with an incoming
message.
?– Length: The length ?¬?eld de?¬?nes the length of the information ?¬?eld. This ?¬?eld is not
important for general troubleshooting.
The last four ?¬?elds might not appear in all the PPP messages, depending on the purpose of
the message.
Summary of Establishing a Point-to-Point WAN Connection with PPP
The following summarizes the key points that were discussed in the previous sections:
?– PPP is a common Layer 2 protocol for the WAN. Two components of PPP exist: LCP
negotiates the connection and NCP encapsulates traf?¬?c.
Establishing a WAN Connection with Frame Relay 325
?– You can con?¬?gure PPP to use PAP or CHAP. PAP sends everything in plain text. CHAP
uses an MD5 hash.
?– Common PPP veri?¬?cation commands include show interface to verify PPP
encapsulation and debug ppp negotiation to verify the LCP handshake.
Establishing a WAN Connection with Frame Relay
Frame Relay is a high-performance WAN protocol that was standardized by the ITU-T and
is widely used in the United States. This section describes Frame Relay operation,
con?¬?guration, and troubleshooting.
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