The
physical demarcation point is the place where the responsibility for the connection
changes from the user to the service provider. This is important because when problems
arise, both sides of the link need to prove that the problem either resides with them or not.
Figure 5-6 illustrates how a router interconnects different LANs through a WAN segment.
The management ports provide a text-based connection that allows for con?¬?guration and
troubleshooting of a router. The common management interfaces are the console and
auxiliary ports. These ports are connected to a communications port on a computer. The
computer must run a terminal emulation program to provide a text-based session with the
router, which enables you to manage the device.
NOTE To support higher densities in a smaller form factor, Cisco introduced a smart
serial cable. The serial end of the smart serial cable is a 26-pin connector. It is much
smaller than the DB-60 connector that connects to a ?¬?ve-in-one serial port. These
transition cables support the same ?¬?ve serial standards, are available in either DTE or
DCE con?¬?guration, and are used with two-port serial connections and two-port
asynchronous and synchronous WICs.
354 Chapter 5: WAN Connections
Figure 5-6 Routers Use the WAN to Connect Remote LANs
WAN Data Link Layer Protocols
In addition to physical layer devices, WANs require data link layer protocols to establish
the link across the communication line from the sending to the receiving device.
Pages:
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493