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̈ Chapter 7: Routing and WAN connections LANCOM Reference Manual LCOS 3.50
93
Routing and WAN
connections
The phases of PPP negotiation
Establishment of a connection using PPP always begins with a negotiation of
the parameters to be used for the connection. This negotiation is carried out
in four phases which should be understood for the sake of configuration and
troubleshooting.
̈ Establish phase
Once a connection has been made at the data communication level,
negotiation of the connection parameters begins through the LCP.
This ascertains whether the remote site is also ready to use PPP, and the
packet sizes and authentication protocol (PAP, CHAP, MS-CHAP or none)
are determined. The LCP then switches to the opened state.
̈ Authenticate phase
Passwords will then be exchanged, if necessary. The password will only be
sent once if PAP is being used for the authentication process. An
encrypted password will be sent periodically at adjustable intervals if
CHAP or MS CHAP is being used.
Perhaps a callback is also negotiated in this phase via CBCP (Callback
Control Protocol).
̈ Network phase
LANCOM, supports the protocols IPCP and IPXCP.
After the password has been successfully transmitted, the IPCP and/or
IPXCP network layer can be established.
IP and/or IPS packets can be transferred from the router modules to the
opened line if the negotiation of parameters is successful for at least one
of the network layers.
̈ Terminate phase
In the final phase the line is cleared, when the logical connections for all
protocols are cleared.
PPP negotiation in the LANCOM
The progress of a PPP negotiation is logged in the devices' PPP statistics and
the protocol packets listed in detail there can be used for checking purposes
in the event of an error.
The PPP trace outputs offer a further method of analysis. You can use the com-
mand
trace + ppp