Explain basic switching concepts and the operation of Cisco switches (13 questions)

QUESTION NO: 1

You want to influence the root bridge selection within the TestKing LAN. Which two values are used by spanning tree protocol to elect a root bridge? (Choose two.) A. Amount of RAM

B. Speed of the links C. IOS Version

A TestKing Ethernet switch receives a unicast frame with a destination MAC that is listed in the switch table. What will this switch do with the frame?

A. The switch will forward the frame to a specific port

B. The switch will forward the frame to all ports except the port on which it was received C. The switch will return a copy of the frame out the source port

D. The switch will not forward unicast frames

E. The switch will remove the destination MAC from the switch table F. None of the above.

Answer: A Explanation:

How Does the Switch Find Host MACs?

Let's use the diagram below to help us understand how address learning process takes place.

Let's assume that we have just powered on the switch. It has nothing in its MAC table.

We connect the cables from the hosts on the switch interfaces as shown in the diagram.

Host A initiates a connection towards Host D, and the following takes place:

1. Host A (interface fe0/0) sends a frame to Host D (MAC address:0000.43c5.334c).

2. The switch inspects the Source Address in the frame and notes in its table the MAC address of Host A along with the Interface number from which the frame originated.

3.

The switch inspects the Destination Address in the frame. Since it does not have Hosts D MAC address in its table, it constructs a broadcast frame and forwards out all interfaces except the interface from where the original frame arrived.

4. Host D identifies itself as the expected recipient and responds back to Host A. The

switch receives the respond frame on interface fe0/11 and places the SA in its table along with the interface number where the frame came from.

5. From now on, further communication between the two hosts will be switched to the appropriate interfaces based on the MAC tables entries.

This process takes place every time a new host is attached on the switch and initiates traffic. The switch tries to keep its MAC table up-to-date, therefore if some hosts do not initiate traffic for a certain amount of time, the switch removes them from its table and reinserts them when they begin sending traffic.

Reference:

http://www.trainsignaltraining.com/studying-for-your-ccent-learn-all-about-switching-and-stp/2007-11-01/

QUESTION NO: 3

In which circumstance are multiple copies of the same unicast frame likely to be transmitted in the TestKing Switched LAN?

A. During high traffic periods

B. In an improperly implemented redundant topology C. After broken links are re-established

D. When upper-layer protocols require high reliability E. When a dual ring topology is in use

F. None of the above

Answer: B Explanation:

A redundant topology eliminates single points of failure, but it also causes broadcast storms, multiple frame copies, and MAC address table instability problems. Multiple Frame Copies--when a new switch is added, the other switches may not have learned its correct MAC address. The host may send a unicast frame to the new switch. The frame is sent through several paths at the same time. The new switch will receive several copies of the frame. This causes MAC database instability. MAC database instability results when multiple copies of a frame arrive on different ports of a switch. Layer 2 has no

mechanism to stop the loop. This is the main reason for the Spanning Tree Protocol(STP) IEEE 802.1d which was developed to prevent routing loops.

If multiple connections between switches are created for redundancy purposes, network loops can occur iin an imprperly designed topology. Spanning Tree Protocol (STP) is used to stop network loops while still permitting redundancy.

QUESTION NO: 4

Part of the TestKing switched LAN is shown below:

Based on the information show above, which device will provide the spanning-tree designated port role for the TestKing network segment that services the printers?

A. Switch TestKingA B. Hub TestKingE C. Switch TestKingC D. Switch TestKingB E. Switch TestKingD

F. None of the switches will provide the designated port role

Answer: C

QUESTION NO: 5

The TestKing network administrator needs to a switch named TK1 to become the root bridge for a redundant path switched network. What can be done to ensure that TK1 will always assume the role as the root bridge?

A. Assign the switch a higher MAC address than the other switches in the network have B. Establish a direct link from the switch to all other switches in the network

C. Configure the switch full-duplex operation and configure the other switches for half-duplex operation

D. Configure the switch so that it has lower priority than other switches in the network E. None of the above

Answer: D

QUESTION NO: 6

Four TestKing PCs connect to a single switch as shown below:

In the TestKing network shown above, switch TestKing1 has just been restarted and has passed the POST routine. Host TestKingA (the one on the left) sends its initial frame to Host TestKingC. What is the first thing the switch will do as regards to populating the switching table?

A. Switch TestKing1 will add 192.168.23.12 to the switching table B. Switch TestKing1 will add 192.168.23.4 to the switching table C. Switch TestKing1 will add 000B.DB95.2EE9 to the switching table D. Switch TestKing1 will add 000A.8A47.E612 to the switching table E. None of the above

Answer: D

QUESTION NO: 7

TK1 is a switch in the TestKing network. Why will TK1 never learn the broadcast address?

A. Broadcast frames are never sent to switches B. A broadcast frame is never forwarded by a switch C. Broadcasts only use network layer addressing

D. A broadcast address will never be the source address of a frame E. Broadcast addresses use an incorrect format for the switching table F. None of the above

Answer: D