Chapter 7. Configuring and Verifying Switch Interfaces

Question 1

1. Which of the following describes a way to disable IEEE standard autonegotiation on a 10/100 port on a Cisco switch?
   a) .Configure the [negotiate disable] interface subcommand
   b) .Configure the [no negotiate] interface subcommand
   c) .Configure the [speed 100] interface subcommand
   d) .Configure the [duplex half] interface subcommand
   e) .Configure the [duplex full] interface subcommand
   f) .Configure the [speed 100] and [duplex full] interface subcommands

Answer 1

1. F. Cisco switches do not have a command to disable autonegotiation of speed and duplex. Instead, a switch port that has both [speed] and [duplex] configured disables autonegotiation.

Question 2

2. In which of the following modes of the CLI could you configure the duplex setting for interface Fast Ethernet 0/5?
   a) .User mode
   b) .Enable mode
   c) .Global configuration mode
   d) .VLAN mode
   e) .Interface configuration mode

Answer 2

2. E. Cisco switches can be configured for speed (with the [speed] command) and duplex (with the [duplex] command) in interface configuration mode.

Question 3

3. A Cisco Catalyst switch connects with its Gigabit0/1 port to an end user’s PC. The end user, thinking the user is helping, manually sets the PC’s OS to use a speed of 1000 Mbps and to use full duplex, and disables the use of autonegotiation. The switch’s G0/1 port has default settings for speed and duplex. What speed and duplex settings will the switch decide to use? (Choose two answers.)
   a) .Full duplex
   b) .Half duplex
   c) .10 Mbps
   d) .1000 Mbps

Answer 3

3. A and D. The IEEE autonegotiation rules dictate that if a device attempts autone-gotiation but the other side does not participate, use the slowest speed it supports. However, Cisco switches override that logic, instead sampling the electrical signal to detect the speed used by the connected device, so the switch will operate at 1000 Mbps. The switch uses the IEEE default setting for duplex based on the speed, and the IEEE default for duplex when using 1000 Mbps is to use full duplex. So in this case, the switch will match both the speed and the duplex setting made on the PC.

Question 4

4. The output of the [show interfaces status] command on a 2960 switch shows inter-face Fa0/1 in a “disabled” state. Which of the following is true about interface Fa0/1? (Choose three answers.)
   a) .The interface is configured with the [shutdown] command.
   b) .The [show interfaces fa0/1] command will list the interface with two status codes of administratively down and line protocol down.
   c) .The [show interfaces fa0/1] command will list the interface with two status codes of up and down.
   d) .The interface cannot currently be used to forward frames.
   e) .The interface can currently be used to forward frames.

Answer 4

4. A, B, and D. The disabled state in the [show interfaces status] command is the same as an “administratively down and down” state shown in the [show interfaces] command. The interface must be in a connected state (per the [show interfaces status] command) before the switch can send frames out the interface.

Question 5

5. Switch SW1 uses its Gigabit 0/1 interface to connect to switch SW2’s Gigabit 0/2 inter-face. SW2’s Gi0/2 interface is configured with the [speed 1000] and [duplex full] com-mands. SW1 uses all defaults for interface configuration commands on its Gi0/1 interface. Which of the following are true about the link after it comes up? (Choose two answers.)
   a) .The link works at 1000 Mbps (1 Gbps).
   b) .SW1 attempts to run at 10 Mbps because SW2 has effectively disabled IEEE stan-dard autonegotiation.
   c) .The link runs at 1 Gbps, but SW1 uses half duplex and SW2 uses full duplex.
   d) .Both switches use full duplex.

Answer 5

5. A and D. SW2 has effectively disabled IEEE standard autonegotiation by configuring both speed and duplex. However, Cisco switches can detect the speed used by the other device, even with autonegotiation turned off. Also, at 1 Gbps, the IEEE autone-gotiation standard says to use full duplex. If the duplex setting cannot be negotiated, both ends use 1 Gbps, full duplex.

Question 6

6. Switch SW1 connects via a cable to switch SW2’s G0/1 port. Which of the following conditions is the most likely to cause SW1’s late collision counter to continue to increment?
   a. SW2’s G0/1 has been configured with a [shutdown] interface subcommand.
   b. The two switches have been configured with different values on the [speed] interface subcommand.
   c. A duplex mismatch exists with SW1 set to full duplex.
   d. A duplex mismatch exists with SW1 set to half duplex.

Answer 6

6. D. For the two answers about a duplex mismatch, that condition does cause collisions, particularly late collisions, but only the side using CSMA/CD logic (the half-duplex side) has any concept of collisions. So, if switch SW1 was using half duplex, and switch SW2 using full duplex, SW1 would likely see late collisions and see that coun-ter increment over time.
   If switch SW2 had shut down its interface, switch SW1’s interface would be in a down/down state, and none of the counters would increment. Also, if both switch ports had been configured with different speeds, again the ports would be in a down/down state, and none of the interface counters would increment.