Vol 1 Part 2: Implementing Ethernet LANs

Question 1

All interfaces by default reside on which vlan?

Answer 1

VLAN 1, also known as the default VLAN

Question 2

What is the difference between END and EXIT?

Answer 2

End brings you back to enable mode, exit brings you back up one level in the configuration mode.

Question 3

What are the 3 things a switch is responsible for performing?

Answer 3

Whether to forward or filter a frame, learning the source MAC address for storage in the CAM table, and forwarding the frame with a layer 2 loop-free environment via the Spanning Tree Protocol (STP).

Question 4

What does AAA stand for, what is it used for, and what types of services do we use to obtain AAA?

Answer 4

Authentication, authorization, and accounting. It is used for securing credentials for remote access ie. SSH and Telnet. TACACS+ and RADIUS are the most commonly used services for AAA.

Question 5

What are the 4 types of memory in a cisco switch, and what is stored in each memory?

Answer 5

RAM- stores working memory and running config
Flash- stores the Cisco IOS
ROM- stores the bootstrap program
NVRAM- stores the startup config

Question 6

Why is Telnet considered undesirable?

Answer 6

It is unsecure due to plain text input

Question 7

Explain the IEEE rules for auto negotiation, as well as the Cisco rules (hint, there’s 2 rules for each!)

Answer 7

IEEE Rule 1: Use the slowest speed supported
IEEE Rule 2: If speed is 10 or 100, use half duplex. Otherwise, full duplex.
Cisco Rule 1: Sense the speed. If speed cannot be sensed, use slowest speed supported.
Cisco Rule 2: Same as IEEE rule 2

Question 8

Which Cisco switch is the most commonly used today?

Answer 8

The Cisco 2960XR

Question 9

What commands are used to show the CAM table? (Hint, there are 2, as the second one shows us slightly different information)

Answer 9

Show mac-address table and Show mac-address table dynamic. The first one shows all of the MAC addresses and the ports on the switch, while the second one just shows the addresses the switch has learned on its own (dynamically).

Question 10

What does the shutdown command do, and what can we learn by examining the status of the interfaces on the switch with respect to the shutdown command?

Answer 10

The shutdown command turns off an interface. If we look a the list of interfaces on the switch and see that an interface is administratively down, then we know that someone shutdown the port manually.

Question 11

What is Line VTY used for?

Answer 11

Remote access via telnet/SSH

Question 12

What commands are used in order to configure SSH?

Answer 12

Hostname, IP domain-name, Crypto key generate rsa, Username/secret, Line vty 0 15, Login local

Question 13

What happens if a switch receives a frame that has a destination MAC address not currently in the CAM table?

Answer 13

The frame is forwarded/flooded out on all ports except the source. The port with the corresponding MAC address responds to the switch with the MAC address, and the switch creates a new entry in the CAM table for that MAC address.

Question 14

What happens to a frame if there is no entry for it on the MAC table and there is no response received from any interface after the switch has sent a flooded broadcast message?

Answer 14

It will drop the frame

Question 15

What is a late collision and what does it mean for our network if we are experiencing late collisions?

Answer 15

Late collisions are the collisions that occur after the 64th byte has been transmitted. Ideally, collisions occur before the 64th byte, and if we experience late collisions, then we most likely have a duplex mismatch?

Question 16

What command is used to encrypt plain text passwords on the switch?

Answer 16

service password-encryption

Question 17

What is the show command used for?

Answer 17

To show all available commands that can be utilized with whatever command is typed in after the word show in the CLI. This is helpful in the event that you forget what command you need to use.

Question 18

What does it mean if an engineer is bouncing a port?

Answer 18

He is issuing a shutdown command followed by a no shutdown command.

Question 19

What are the two types of modes when accessing a switch and what are the differences?

Answer 19

User mode and privileged mode (also known as enable mode). User mode allows a user to view limited items and make no changes. Enable mode allows the user to execute admin level commands and view all settings in the switch.

Question 20

Why is SSH the preferred method for remote access into a switch?

Answer 20

The connection is encrypted.

Question 21

What on the switch is used to connect devices? Give BOTH names

Answer 21

Ports/Interfaces

Question 22

What 2 commands are used to set up a privileged password for enable mode, and what are the differneces?

Answer 22

enable password and enable secret. Enable password is plain text while enable secret is hashed. Remember! enable secret supersedes enable password.

Question 23

What is the default MAC Table time, and how can you change it?

Answer 23

300 seconds. Can be changed using the mac address-table agingtime command.

Question 24

How do you store the running config and start up config in the NVRAM?

Answer 24

By using the command “copy running-config startup config” or “copy run start” for short

Question 25

What does a switch look at in order to learn new MAC addresses for the CAM table?

Answer 25

The source MAC address of the frame it received.

Question 26

How do you configure IPv4 on a layer 2 switch?

Answer 26

Interface VLAN 1, ip address, no shutdown, ip default-gateway

Question 27

What is a runt?

Answer 27

A frame that is less than 64 bytes. REMEMBER! A switch will pad that frame in order to get it up to 64 bytes.

Question 28

What is the difference between TACACS+ and RADIUS?

Answer 28

TACACS+ is Cisco proprietary and utilizes TCP. Radius is vendor neutral and utilizes UDP.

Question 29

Why do we need an IPv4 address on a switch, and where do we usually assign this IP address?

Answer 29

To enable management and remote access. It is usually assigned to a VLAN other than the default VLAN.

Question 30

What is a baby giant?

Answer 30

A frame that is more than 1518 bytes but less than 1600.

Question 31

What are the three ways to connect to a switch?

Answer 31

Telnet, SSH, and Console

Question 32

What is a roll over cable?

Answer 32

A cable that allows a person to console into a switch. It utilizes a serial connection on one end and an RJ-45 connection on the other.

Question 33

What does the IP Default-Gateway command enable?

Answer 33

A gateway for the switch if it does not know how to handle the packet.

Question 34

How do you erase the NVRAM in order to get a clean switch?

Answer 34

Write erase, Erase start, Erase nvram, RELOAD

Question 35

What does the No command do?

Answer 35

Removes the configurations you have set on an interface

Question 36

What command is entered in order to access Global Configuration Mode?

Answer 36

Configure Terminal, also known as config t or conf t.

Question 37

Explain the logging console commands (hint, there’s 4 of them)

Answer 37

Logging console turns on logging. No logging console turns off logging. Logging synchronous sets SYSLOG messages to create new lines for themselves in order to reduce clutter, Exec-timeout sets the timeout time in the console for SYSLOG messages.

Question 38

The console port is known as what in the Command Line Interface (CLI)?

Answer 38

Line Con 0

Question 39

What 3 things MUSt we have in order to configure SSH?

Answer 39

A unique hostname, an ip domain name, and keys generated with RSA

Question 40

What are the desired settings when using a console emulator?

Answer 40

9600bits/second, No hardware flow control, 8-bit ASCII, No parity bits, 1 stop bit