Ccna3 Chapter 2

Front 1

Logical Layer 2 loops may occur due to

Back 1

the learning and forwarding process.

Front 2

Ethernet frames do not have a

Back 2

time to live (TTL) attribute.

Front 3

Ethernet frames continue to propagate between switches endlessly. This continued propagation between switches can result in

Back 3

MAC database instability.

Front 4

Instability occurs due to

Back 4

constant changes in mac address table resulting in high cpu load.

Front 5

A broadcast storm occurs when

Back 5

there are broadcast frames caught in a Layer 2 loop and all available bandwidth is consumed.

Front 6

Unicast frames sent onto a looped network can result in

Back 6

duplicate frames arriving at the destination device.

Front 7

Spanning tree is enabled, by default, on Cisco switches to

Back 7

prevent Layer 2 loops from occurring.

Front 8

STP ensures that

Back 8

there is only one logical path between all destinations on the network.

Front 9

Blocking the redundant paths is critical to

Back 9

preventing loops on the network.

Front 10

The physical paths still exist to provide redundancy, but these paths are disabled to

Back 10

prevent the loops from occurring.

Front 11

The Spanning Tree Algorithm designates a switch as the

Back 11

root bridge and uses it as the reference point for all path calculations.

Front 12

All switches that are participating in STP

Back 12

exchange BPDU frames to determine which switch has the lowest bridge ID (BID).

Front 13

The switch with the lowest BID automatically becomes the

Back 13

root bridge for the STA calculations.

Front 14

After a switch boots it begins to send out BPDU frames every

Back 14

two seconds.

Front 15

BPDU frames that are sent contain the BID of the

Back 15

local switch as the root ID.

Front 16

Each switch maintains local information about

Back 16

its own BID, the root ID, and the path cost to the root.

Front 17

When adjacent switches receive a BPDU frame, theycompare the

Back 17

root ID from the BPDU frame with the local root ID.

Front 18

If the root ID in the BPDU is lower than the local root IDthe switch

Back 18

updates the local root ID and the ID in its BPDU messages.

Front 19

The BID is made up of a

Back 19

priority value, an extended system ID, and the MAC address of the switch.

Front 20

The extended system ID value isadded to the bridge priority value in the BID to

Back 20

identify the priority and VLAN of the BPDU frame.

Front 21

The BID is only taken into account if

Back 21

path costs are equal.

Front 22

After the root bridge has been determined, the STA calculatesthe

Back 22

shortest path to the root bridge.

Front 23

The STA considers both path and port costs when determining which

Back 23

ports to block.

Front 24

The sum of the port cost values determinesthe overall

Back 24

path cost to the root bridge.

Front 25

Paths with the lowest cost become

Back 25

preferred.

Front 26

The default port costs are defined by

Back 26

the speed at which the port operates.

Front 27

10 Gb/s Ethernet ports have a port cost of

Back 27

2

Front 28

1 Gb/s Ethernet ports have a port cost of

Back 28

4

Front 29

100 Mb/s Fast Ethernet ports have a port cost of

Back 29

19

Front 30

10 Mb/s Ethernet ports have a port cost of

Back 30

100

Front 31

Although switch ports have a default port cost associated with them, the port cost is

Back 31

configurable.

Front 32

The ability to configure individual port costs givesthe administrator the flexibility to

Back 32

manually control the spanning tree paths to the root bridge.

Front 33

Generally, the switch with the lower BID has its port configured as a

Back 33

designated port.

Front 34

The switch with the higher BID has its port configured as an

Back 34

alternate port.

Front 35

The first priority is the lowestpath cost to the

Back 35

root bridge.

Front 36

The sender’s BID is used only if

Back 36

port costs are equal.

Front 37

Port roles

Back 37

Root ports

Designated ports

Alternate and backup ports

Disabled ports

Front 38

Root ports

Back 38

Switch ports closest to the root bridge.

Front 39

Designated ports

Back 39

All non-root ports that are still permitted to forward traffic on the network.

Front 40

Alternate and backup ports are configured to be in a

Back 40

blocking state to prevent loops.

Front 41

Disabled ports are switch ports that are

Back 41

shut down.

Front 42

If the root ID from a BPDU received is lower than the root ID on the receiving switch, thenthe receiving switch

Back 42

updates its root ID, identifying the adjacent switch as the root bridge.

Front 43

There is a root bridge electedfor each

Back 43

spanning tree instance.

Front 44

There is only one STP instance

Back 44

per VLAN.

Front 45

The switch uses the customizable port priority value to

Back 45

break the path cost tie.

Front 46

If the customizable port priority value on each port is at the default value the lowest

Back 46

port ID is used.

Front 47

The extended system ID value is added to the bridge priority value in the BID to

Back 47

identify the priority and VLAN of the BPDU frame.

Front 48

Priority is the initial deciding factor when

Back 48

electing a root bridge.

Front 49

If the priorities and extended system ID's of all the switches are the same, the device with the lowest

Back 49

MAC address becomes the root bridge.

Front 50

Bridge Priority >

Back 50

Extended System ID

Front 51

Extended System ID >

Back 51

MAC Address