DIGITAL GIGAswitch/Router User Reference Manual
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Point-to-Point Protocol (PPP) Overview
Point-to-Point Protocol (PPP) Overview
Because of its ability to quickly and easily accommodate IP and IPX protocol traffic, Point-
to-Point Protocol (PPP) routing has become a very important aspect of WAN
configuration. Using PPP, you can set up router-to-router, host-to-router, and host-to-host
connections.
Establishing a connection in a PPP environment requires that the following events take
place:
•
The router initializing the PPP connection transmits Link Control Protocol (LCP)
configuration and test frames to the remote peer to set up the data link.
•
Once the connection has been established, the router which initiated the PPP
connection transmits a series of Network Control Protocol (NCP) frames necessary to
configure one or more network-layer protocols.
•
Finally, when the network-layer protocols have been configured, both the host and
remote peer can send packets to one another using any and all of the configured
network-layer protocols.
The link will remain active until explicit LCP or NCP frames instruct the host and/or the
peer router to close the link, or until some external event (i.e., user interruption or system
time-out) takes place.
You can set up PPP ports on your GSR with the commands described in Chapter 32: “port
Commands” in the
DIGITAL GIGAswitch/Router Command Line Interface Reference Manual
.
Use of LCP Magic Numbers
LCP magic numbers enable you to detect situations where PPP LCP packets are looped
back from the remote system, resulting in an error message. The use of LCP magic
numbers is enabled on the GSR by default; however, should you employ a service profile
in which the use of LCP magic numbers has been disabled, undetected “loopback”
behavior may become a problem.
Note:
In the event that a PPP WAN interface remains unrecognized at startup due to
loopback interference, you can use the
ppp restart
command in the CLI to remedy
the situation.
