CCNA Cisco Certified Network Associate Study Guide - FTP Server

496 Chapter 10 � Wide Area Networking Protocols
RouterA(config)#int s0.?
Serial interface number
RouterA(config)#int s0.16 ?
multipoint Treat as a multipoint link
point-to-point Treat as a point-to-point link
You can define an almost limitless number of subinterfaces on a given
physical interface (keeping router memory in mind). In the above example,
we chose to use subinterface 16 because that represents the DLCI number
assigned to that interface. However, you can choose any number between 0
and 4,292,967,295.
There are two types of subinterfaces:
Point-to-point Used when a single virtual circuit connects one router to
another. Each point-to-point subinterface requires its own subnet.
Multipoint Used when the router is the center of a star of virtual circuits.
Uses a single subnet for all routers’ serial interfaces connected to the
frame switch.
An example of a production router running multiple subinterfaces is
shown below. Notice that the subinterface number matches the DLCI number.
This is not a requirement but helps in the administration of the interfaces.
Also notice that there is no LMI type defined, which means they are
running either the default of Cisco or using autodetect if running Cisco IOS
version 11.2 or newer. This configuration was taken from one of my customers’
production routers (used by permission). Notice that each interface
is defined as a separate subnet, separate IPX network, and separate Apple-
Talk cable range (AppleTalk is beyond the scope of this course):
interface Serial0
no ip address
no ip directed-broadcast
encapsulation frame-relay
!
interface Serial0.102 point-to-point
ip address 10.1.12.1 255.255.255.0
no ip directed-broadcast
appletalk cable-range 12-12 12.65
appletalk zone wan2