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Switch Interfaces

The first example assumes that you installed the switch and cabling correctly, and that the
switch interfaces work. Once you do the installation and connect to the Console, you can
easily check the status of those interfaces with the show interfaces status command, as
shown in Example 7-2.

Example 7-2 show interfaces status on Switch SW1
Free CISCO CCNA Routing and Switching ICND1 Study Guide

Focus on the port column for a moment. As a reminder, Cisco Catalyst switches name
their ports based on the fastest specification supported, so in this case, the switch has
24 interfaces named Fast Ethernet, and two named Gigabit Ethernet. Many commands
abbreviate those terms, this time as Fa for Fast Ethernet and Gi for Gigabit Ethernet. (The
example happens to come from a Cisco Catalyst switch that has 24 10/100 ports and two
10/100/1000 ports.)

The Status column of course tells us the status or state of the port. In this case, the lab
switch had cables and devices connected to ports F0/1–F0/4 only, with no other cables
connected. As a result, those first four ports have a state of connected, meaning that the ports have a cable and are functional. The notconnect state means that the port is not yet
functioning. It may mean that there is no cable installed, but other problems may exist
as well. (The section “Analyzing Switch Interface Status and Statistics,” in Chapter 12,
“Troubleshooting Ethernet LANs,” works through the details of what causes a switch interface
to fail.)

NOTE You can see the status for a single interface in a couple of ways. For instance, for
F0/1, the command show interfaces f0/1 status lists the status in a single line of output as
in Example 7-2. The show interfaces f0/1 command (without the status keyword) displays
a detailed set of messages about the interface.

The show interfaces command has a large number of options. One particular option, the
counters option, lists statistics about incoming and outgoing frames on the interfaces. In
particular, it lists the number of unicast, multicast, and broadcast frames both the in and out
direction, and a total byte count for those frames. Example 7-3 shows an example, again for
interface F0/1.

Example 7-3 show interfaces f0/1 counters on Switch SW1
Free CISCO CCNA Routing and Switching ICND1 Study Guide

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