Ccnp Switch 642-813: Stp Options

Front 1

What three STP methods can be used to improve convergence?

Back 1

PortFast
UplinkFast
BackboneFast

Front 2

Where should PortFast be enabled?

Back 2

On Access-Layer nodes with ports connected to end user devices.

Front 3

Does PortFast disable STP on a port?

Back 3

No

Front 4

On ports with PortFast enabled, are STP TCNs sent when the port goes up or down?

Back 4

No

Front 5

Is PortFast configured globally or per-port?

Back 5

Either

Front 6

What is UplinkFast?

Back 6

Enables fast-uplink on an access-layer switch when dual uplinks are connected to the distribution switch.

Front 7

Where do you configure UplinkFast?

Back 7

Access switches with dual uplink ports to distribution switches.
(NEVER on a Root switch)

Front 8

Is UplinkFast configured globally, per-port, or per-VLAN?

Back 8

Globally

Front 9

What happens when UplinkFast is triggered?

Back 9

Redundant uplink port is quickly brought up and MACs are flooded out.

Front 10

What two values are changed by UplinkFast?

Back 10

Bridge priority
Port Costs

Front 11

What is the bridge priority set to when UplinkFast is used?

Back 11

49,152

Front 12

What are the port costs incremented by with UplinkFast?

Back 12

3,000

Front 13

What is BackboneFast?

Back 13

An STP feature that can detect an indirect link failure and shorten STP convergence time to 30 seconds by bypassing the Max Age timeout period.

Front 14

Where do you configure BackboneFast?

Back 14

All switches (due to RLQ)

Front 15

Is BackboneFast configured globally or per-port?

Back 15

Globally

Front 16

What happens when BackboneFast is triggered?

Back 16

Max Age timer is bypassed, shortening convergence time.

Front 17

What is Root Link Query (RLQ)?

Back 17

Protocol used by BackboneFast to see whether upstream switches have stable connections to the root bridge

Front 18

What two STP methods can be used to protect against unexpected BPDUs?

Back 18

Root Guard
BPDU Guard

Front 19

What is Root Guard?

Back 19

It prevents a port from becoming the root port even if superior BPDUs are heard (basically makes the port unable to receive BPDUs but it can forward them)

Front 20

Where do you configure Root Guard?

Back 20

1. Distribution switch ports facing access switches.
2. On switch ports that should never connect to a root bridge (access ports).

Front 21

What happens when Root Guard is triggered?

Back 21

Port is put in a "root-inconsistent" state until the BPDUs cease.

Front 22

Does Root Guard affect a port or VLAN?

Back 22

Port

Front 23

What is the Root-inconsistent port state?

Back 23

State a port will enter when configured with Root Guard and a superior BPDU is detected.
NO data Tx/Rx, listen to BPDUs only

Front 24

What does BPDU Guard do?

Back 24

Prevents loops on ports in PortFast mode.

Front 25

What happens when BPDU Guard is triggered?

Back 25

Puts ports in PortFast mode into the "errdisable" state upon receiving a BPDU.

Front 26

Does BPDU Guard affect a port or VLAN?

Back 26

Port

Front 27

Where do you configure BPDU Guard?

Back 27

Globally or per-port.

Front 28

What two STP methods can be used to protect against the sudden loss of BPDUs?

Back 28

Loop Guard
UDLD

Front 29

What is Loop Guard?

Back 29

Tracks BPDU activity on non-designated ports and moves it to the "loop-inconsistent" state when BPDUs stop being received.

Front 30

Where do you configure Loop Guard?

Back 30

1. Ports between distribution switches
2. Uplink ports from access to distribution switches

Front 31

What happens when Loop Guard is triggered?

Back 31

Port is put into the "loop-inconsistent" state until BPDUs are received again.

Front 32

Does Loop Guard affect a port or VLAN?

Back 32

VLAN: but it is configured per port or globally

Front 33

What is Unidirectional Link Detection (UDLD)?

Back 33

Monitors a port to see if it is actually operating bidirectionally.

Front 34

Where do you configure UDLD?

Back 34

All switch ports (fiber ports)

Front 35

What are the two UDLD modes?

Back 35

Normal
Aggressive

Front 36

What happens when UDLD is triggered?

Back 36

Normal mode: continued operation, event logged
Aggressive mode: errdisable state

Front 37

What layer does UDLD operate at?

Back 37

Layer 2

Front 38

What does UDLD send to the other end of the link?

Back 38

Echos

Front 39

Does UDLD affect a port or VLAN?

Back 39

Port

Front 40

What is the default UDLD message timer?

Back 40

15 seconds

Front 41

What is UDLD Aggressive Mode?

Back 41

When UDLD condition is detected, UDLD message sent out for 8 seconds, then port is placed in the "errdisable" state.

Front 42

What is UDLD Normal Mode?

Back 42

When UDLD condition is detected, port is allowed to continue to operate and the action is logged.

Front 43

How do you block all BPDUs on a port?

Back 43

Enable BPDU filtering.

Front 44

What does BPDU filtering do?

Back 44

Prevents BPDUs from being sent or processed on a port.

Front 45

Is BDPU filtering enabled globally on all ports or per-port?

Back 45

Either

Front 46

When BPDU Filtering is configured globally, what happens to a PortFast enabled port when it receives a BPDU?

Back 46

The port immediately loses its operational PortFast status and BPDU Filtering is disabled and it resumes sending BPDUs.

Front 47

When BPDU Filtering is configured specifically for a port, what happens to a PortFast enabled port when it receives a BPDU?

Back 47

It ignores all BPDUs it receives and sends no BPDUs.