Ch 2 - RSTP

Question 1

What is the IEEE protocol for RSTP

Answer 1

802.1w as an amendment to 802.1D. Later in 2004 was included in 802.1D known as 802.1d-2004 Loc: 2867

Question 2

What does RSTP call the ‘Blocking State’?

Answer 2

Discarding State Loc: 2908

Question 3

What is the RSTP Alternate Port?

Answer 3

Replaces the Root Port when the Root Port fails. Loc: 2942

Question 4

What is the RSTP Backup Port?

Answer 4

Replaces the Designated Port when the Designated Port fails.

Question 5

What is the RSTP Disabled Port?

Answer 5

Port that is admin’ed down. Loc: 2899

Question 6

In RSTP what is a Point-to-point Link?

Answer 6

A link with exactly two devices on it running full duplex without portfast configured. Loc: 3004

Question 7

In RSTP, what is a Point-to-point port?

Answer 7

The ports that connect to a point-to-point link. Loc: 3004

Question 8

In RSTP, what is a Point-to-point Edge port?

Answer 8

A type of point-to-point port that connects to a single endpoint at the edge of the network running full duplex with portfast enabled.

Question 9

in RSTP, what is a Shared Port?

Answer 9

A port that connects to a hub and runs half-duplex.

Question 10

What is Etherchannel?

Answer 10

A connection that combines multiple parallel segments of equal speed (up to eight) between the same pair of switches, bundled into an EtherChannel. Loc: 3004

Question 11

What is PortFast?

Answer 11

PortFast allows a switch to immediately transition from blocking to forwarding, bypassing listening and learning states. Can only be used on links with no bridges, switches, or other STP-speaking devices connected. Loc: 3032

Question 12

What is BPDU Guard?

Answer 12

Prevents an unauthorized switch from connecting to a port and taking over Root Bridge. When configured on a switchport it disables the port if any BPDUs are received on it. Also prevents an unauthorized switch from connecting to a port running PortFast. Loc: 3032

Question 13

In RSTP how long is the MaxAge timer?

Answer 13

3 times the Hello timer. Default is 6 seconds.

Question 14

What are the 5 roles ports play in RSTP?

Answer 14

• Root Port
• Alternate Port
• Designated Port
• Backup Port
• Disabled Port

Question 15

What qualifies a port to be an Alternate Port?

Answer 15

Must receive Hello’s from the same Root Switch as the existing Root Port

Question 16

What are the steps a switch goes through to change from a failed Root Port to its Alternate Port?

Answer 16

1. Root Port fails
2. Switch confirms with its neighbor that it is about to change to its Root Port from the failed port to the Alternate Port as new Root Port.
3. Neighbor flushes the required MAC entries
4. Failed RP changes to Disabled Role and Alternate becomes RP
5. New Root Port begins forwarding immediately.

Question 17

When Alternate Port takes over for a Failed RP does it have to wait for any timers?

Answer 17

No.

Question 18

Does RSTP have a Listening State?

Answer 18

No

Question 19

What are the 3 Port States in RSTP?

Answer 19

• Discarding
• Learning
• Forwarding

Question 20

What does RSTP do when there is a topology change?

Answer 20

• RSTP switches tell each other there has been a Topology Change and to Flush all MAC table entries that might cause a loop.
• Ports that were formerly Discarding can transition to Forwarding without a wait.

Question 21

What are the 3 RSTP Link Types?

Answer 21

• Point-to-Point
• Point-to-Point Edge
• Shared

Question 22

What does RSTP do differently on Shared Ports/Links?

Answer 22

RSTP converges more slowly on Shared Ports

Question 23

What is the criteria RSTP uses to classify a port as a Point-to-Point Edge Port?

Answer 23

• Running at Full Duplex
• Has Portfast configured

Question 24

What is the criteria RSTP uses to classify a port as a Point-to-Point Port?

Answer 24

• The port is running at Full Duplex
• The port does NOT have Portfast configured

Question 25

What is the criteria RSTP uses to classify a port as a Shared Port

Answer 25

Any port running at Half Duplex.

Question 26

If a port has Portfast configured what else should be added to that port?

Answer 26

BPDU Guard