All options and values are negotiated simultaneously. To open a connection to the peer, the device transmits this message along with the configuration options and values the sender wishes the peer to support. This table includes description of PPP negotiation packets that are used in both LCP and NCP negotiation: Packet This diagram shows the PPP phase transitions: CHAP = Challenge Handshake Authentication Protocolģ. Once authentication is complete, PPP transitions to the UP phase. Keep in mind that PPP authentication is optional. If PPP authentication (CHAP 2 or PAP 3) is desired on the link, then PPP transitions to this phase. PPP transitions to this phase when it receives an indication that the physical layer is up and ready to be used. This message is seen after the link and PPP are completely brought down: *Mar 3 23:32:50.296: BR0:1 PPP: Phase is DOWN The end result is that PPP is either up or down. The link goes through several phases in the process of PPP negotiation, as shown in this table. Conventionsįor more information on document conventions, refer to the Cisco Technical Tips Conventions.
#Lcp packets are carried in the field of the ppp frame software
This document is not restricted to specific software and hardware versions. For example, if you want to run PPP over ISDN, then all ISDN layers must be up otherwise PPP does not start. Note: PPP negotiation between two peers cannot start unless the lower layer (ISDN, physical interface, dial-up line, and so on) under PPP functions perfectly. Issue this command to enable Millisecond timestamps on the router: Router(config)# service timestamp debug datetime msecįor more information on debug commands, see Important Information on Debug Commands. Issue the encapsulation ppp command to accomplish this. PPP must be enabled on the interfaces on both routers. Readers of this document must ensure that these conditions are met: This document provides a comprehensive method to read debug ppp negotiation command output. However, it is imperative that you understand the debug ppp negotiation command output. The debug ppp negotiation command enables you to view the PPP negotiation transactions, identify the problem or stage when the error occurs, and develop a resolution. A failure in the PPP negotiation between two routers causes the connection to fail. PPP allows two machines on a point-to-point communication link to negotiate various parameters for authentication, compression, and the Layer 3 (元) protocols, such as IP.
In dial-related applications, PPP is the most commonly used encapsulation type.
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