| When DDR (or a user) creates an
end-to-end path over the ISDN, some method of datagram encapsulation
is needed to provide data connectivity. Available encapsulations for
ISDN designs are PPP, HDLC, and X.25. The X.25 encapsulation type
can also be used for datagram delivery over the D channel. Most internetworking designs
use PPP as the encapsulation.
The encapsulation
ppp command can be used if
you want PPP encapsulation for your ISDN interface. This is the case
if you want any of the LCP options that PPP offers (for example,
Challenge Handshake Authentication Protocol [CHAP] authentication)
or if you want interoperability between routers from different
companies, such as a Cisco router connecting to a router not
provided by Cisco. You must use PPP, Password Authentication
Protocol (PAP), or CHAP if you receive calls from more than one
dialup source. To revert from PPP encapsulation to the default, use
the encapsulation hdlc
command.
Router(config-if)#encapsulation [ppp | hdlc]
Router(config-if)#ppp authentication [chap | pap
|