Switching

Question 0

Main role of LAN switch

Answer 0

Forward Ethernet frames using logic:
1. Decides to forward or filter frame via Dest. MAC
2, Learning MAC address via Source MAC
3. Creating loop free environment via STP
4. Supports full-duplex, doubling its bandwidth available to the device

Question 1

Bridge

Answer 1

A prelude to the switch; separates collision domains

Question 2

If a frame enters the switch and no source MAC is in the table….

Answer 2

The switch creates an entry in its MAC address table

Question 3

Inactivity timer

Answer 3

Timer for each MAC address entry in the MAC address table of switch; resets back to 0 if it receives frame from same MAC address

Question 4

No destination MAC entry in table…

Answer 4

Switch floods unknown unicast, multicast, and broadcast frames to all ports except the incoming port

Question 5

Store-and-forward processing

Answer 5

switch receives the entire frame before forwarding the first bit of the frame

Question 6

cut-through processing

Answer 6

starts sending the frame out the outport asap; propogates errors b/c FCS is in the Ethernet trailer

Question 7

fragment-free processing

Answer 7

receives the first 64 bytes of the frame before forwarding it, reducing errors

Question 8

Full-duplex

Answer 8

allows devices to transmit and receive at the same time, doubling bandwidth

Question 9

LAN switching summary

Answer 9

• Each port provides dedicated bandwidth to a single device
• Allows multiple simultaneous conversations b/n devices on different ports
• Supports rate adaptation (different Ethernet speeds supported)

Question 10

Switches are in ________ of the OSI model

Answer 10

Layer 2

Question 11

If frame is a known unicast address, but outgoing interface is the same is incoming interface….

Answer 11

switch will filter frame, meaning that the switch simply ignores the frame and doesn’t forward it

Question 12

Hubs allow…..

Answer 12

a collision domain to spread from one side of the device to another

Question 13

Only device that can separate broadcast domains are..

Answer 13

Routers

Question 14

Collision domain

Answer 14

a set of NICs for which a frame sent by one NIC could result in a collision with a frame sent by any other NIC in the same collision domain

Question 15

A LAN consists of….

Answer 15

all devices that are on the same broadcast domain

Question 16

Campus LAN

Answer 16

created to support multiple buildings that are in close proximity to each other

Question 17

Access switches

Answer 17

Switches connected directly to end users, providing user access to the LAN

Question 18

Distribution switches

Answer 18

provide a path through which the access switches can forward traffic to each other

Question 19

Core switches

Answer 19

forward traffic between distribution switches

Question 20

Autonegotiation*

Answer 20

each node picks the best options that both nodes support: the fastest speed and the best duplex setting

Question 21

10-BASE-T

Answer 21

CAT3 or better, two pair, 100m

Question 22

100-BASE-T

Answer 22

Fast Ethernet; CAT5 UTP or better; two pair; 100 m

Question 23

1000BASE-T

Answer 23

Gigabit Ethernet; CAT5e UTP or better, four pair; 100 m

Question 24

1000BASE-SX

Answer 24

Multimode fiber; 550 m

Question 25

1000BASE-LX

Answer 25

Multimode fiber; 550 m; 50- and 62.5-micron fiber

Question 26

1000BASE-LX

Answer 26

9-micron single-mode fiber (laser); 5 km

Question 27

IEEE autonegotiation rules

Answer 27

Use slowest speed

If speed is 10, 100 use half duplex; otherwise use full duplex

Question 28

Hub autonegotiation

Answer 28

uses the IEEE rules for choosing default settings, which often results in devices using 10 Mbps and half-duplex

Question 29

The switch CLI can be accessed by three methods…

Answer 29

Telnet, SSH, or the console

Question 30

Console requires…

Answer 30

A connection betweent the serial port of PC and the switch’s console port; rollover cable is needed

Question 31

A difference b/n Telnet and SSH

Answer 31

Telnet sends all data as clear-text data while SSH encrypts this

Question 32

Switches can support up to __ simultaneous Telnet sessions

Answer 32

16

Question 33

SSH requires ____ for login

Answer 33

username and password

Question 34

Debug command

Answer 34

Asks the switch to continue monitoring different processes in the switch.

Question 35

Configuration commands

Answer 35

Are commands that tell the switch the details of what to do and how to do it; changes switch configuration immediately

Question 36

Useful debug commands

Answer 36

no debug all
undebug all
debug

Question 37

RAM memory

Answer 37

Used for working storage (active configuration)

Question 38

ROM memory

Answer 38

stores bootstrap program that finds the full Cisco IOS image and manages the process of loading Cisco IOS into RAM

Question 39

Flash memory

Answer 39

Stores Cisco IOS images and default location where the switch gets its Cisco IOS at boot time

Question 40

NVRAM

Answer 40

stores the initial or startup configuration file

Question 41

reload command

Answer 41

erases RAM and copies start config into RAM

Question 42

erase startup-config or erase nvram

Answer 42

erases startup-configuration file

Question 43

terminal monitor (hint: debug)

Answer 43

EXEC (enable) command that sends a copy of all syslog messages, including debug messages, to the Telnet or SSH user who issues this command