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Chapter 10
Wide Area Networking Protocols
Summary
I
n this chapter, we covered the following key points:
The difference between the following WAN services: X.25/LAPB,
Frame Relay, ISDN/LAPD, SDLC, HDLC, and PPP
Important Frame Relay and X.25 terms and features
The commands to configure Frame Relay LMIs, maps, and sub-
interfaces
The commands to monitor Frame Relay operation in the router
How to identify PPP operations to encapsulate WAN data on Cisco
routers
How to state a relevant use and context for ISDN networking
How to identify ISDN protocols, function groups, reference points,
and channels
How to describe Cisco's implementation of ISDN BRI
Exam Essentials
Remember the default serial encapsulation on Cisco routers. Cisco
routers use a proprietary High-Level Data Link Control (HDLC) encap-
sulation on all their serial links by default.
Understand what the LMI is in Frame Relay. The LMI is a signaling
standard between a CPE device (router) and a frame switch. The LMI is
responsible for managing and maintaining status between these devices.
This also provides transmission keepalives to ensure that the PVC does
not shut down because of inactivity.
Understand the different Frame Relay encapsulations. Cisco uses two
different Frame Relay encapsulation methods on their routers. Cisco is
the default, and means that the router is connected to a Cisco Frame Relay
switch; Internet Engineering Task Force (IETF) means your router is con-
necting to anything but a Cisco Frame Relay switch.
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