Cisco CCNA 2 Instructor Manual page 35

associate did not have or follow standards, then the next associate will need to analyze how
the device is supposed to be connected or configured. For example, if the headquarters router
always has the lowest address in a subnet configured and the remote office uses the next
address up, then there is no question about what the interface addresses should be. The
interface description should provide information about the configuration, connection, and use
of the interface.
3.2.2 Interface descriptions
The description of an interface should be used to identify important information such as a
distant router, a circuit number, or a specific network segment. A description of an interface
can help a network user remember specific information about the interface such as which
network the interface services.
The description is a comment about the interface. Stress the importance of a standard type of
description. Students will use small routers in a small topology and can get physical access to
the routers. Since this is the extent of their experience, it is hard for them to understand how
helpful interface descriptions are.
Ask the students to envision an environment with hundreds of routers, thousands of interfaces,
and routers that are 1000 kilometers (621.4 miles) away. Tell the students that a customer
from a branch office is unable to connect to headquarters. Ask students how they can verify
that the interface is connected to the correct branch office before they change anything on the
interface. There are several good answers such as ask the customer, refer to documentation,
and use the show cdp neighbor command. The best answer is to look at the interface
description with the show interface command.
Ask students the following questions:
•
What is used on an interface to make a comment?
•
Which type of information may be included in a description?
3.2.3 Configuring an interface description
To configure an interface description, enter global configuration mode. From global
configuration mode, enter interface mode. Use the following steps:
1. Enter global configuration mode with the configure terminal command.
2. Enter a specific interface mode such as interface ethernet 0.
3. Enter the description command followed by the information to be displayed. For
example, XYZ network, Building 10.
4. Exit interface mode and return to global configuration mode by pressing Ctrl-Z.
Save the configuration changes to NVRAM with the copy running-config startup-
config command.
Important concepts for students to understand are that each description is for a particular
interface and the description is entered in interface configuration.
34 - 238 CCNA 2: Routers and Routing Basics v3.1 Instructor Guide – Module 3
Copyright © 2004, Cisco Systems, Inc.