CCNP switch slides 15

Question 1

source

Answer 1

http://www.coursehero.com/flashcards/430735/CCNP-SWITCH-642-813-Advanced-Spanning-Tree-Security/

Question 2

What is the IEEE standard for RSTP?

Answer 2

802.1w

Question 3

How do you enable/disable BPDU filtering on a per-port basis?

Answer 3

(if)spanning-tree bpdufilter [enable, disable]

Question 4

What is the IEEE standard for MST?

Answer 4

802.1s

Question 5

What does BPDU guard do to a switchport?

Answer 5

If a BPDU is received on a port with BPDU guard, it is immediately placed into the errDisabled state.

Question 6

What does BPDU filtering do?

Answer 6

It effectively disables STP on a switchport.

Question 7

Can a switch run both MST and PVST+ at the same time?

Answer 7

No! MST relies on the RSTP configuration to operate, and therefor, cannot use PVST+.

Question 8

What does Loop Guard do to switch ports?

Answer 8

It monitors BPDU activity on non-designated ports. When BPDUs go missing, Loop Guard moved the port into a loop-inconsistent state. When BPDUs are received again, the port progresses automatically through the STP states and becomes active.

Question 9

Are the following configuration combinations permissible on a switch port?Root guard and UDLD

Answer 9

Permissible!

Question 10

RSTP uses what BPDU version?

Answer 10

version 2.

Question 11

What is a Cisco proprietary method to detect or prevent the unexpected loss of BPDUs?

Answer 11

Unidirectional Link Detection (UDLD).

Question 12

How many MSTIs can exist in a single MST region?

Answer 12

16. The IST is always MSTI 0, and that leaves MSTI 1-15 open for use.

Question 13

What type of message does RSTP send when negotiating convergence?

Answer 13

It sends a proposal!

Question 14

Are the following configuration combinations permissible on a switch port?Root guard and BPDU guard

Answer 14

NOT-Permissible!

Question 15

What is the relationship between PortFast and BPDU guard?

Answer 15

All ports with PortFast have BPDU guard enabled by default.

Question 16

How does UDLD work to protect STP?

Answer 16

It sends a special UDLD frame to the other end of a link, and that link replies to it to ensure that a link is truly bi-directional.

Question 17

How can you globally enable BPDU filtering on all PortFast ports?

Answer 17

(config)spanning-tree portfast bpdufilter default

Question 18

In RSTP, non-edge ports begin in what RSTP state?

Answer 18

The RSTP discarding state.

Question 19

What does RSTP assume with regard to duplex settings?

Answer 19

That full-duplex links are Point-to-Point and half-duplex links fall back to CST.

Question 20

When should STP Root Guard be used?

Answer 20

On switchports where you never expect to find the root bridge for any VLAN.

Question 21

Within MST what is an IST?

Answer 21

Internal Spanning Tree, it is a locally significant CST bounded by the edges of the MST region.

Question 22

In RSTP how often are BPDUs exchanged?

Answer 22

The default hello timer in RSTP is 2 seconds.

Question 23

What does the ‘spanning-tree link-type point-to-point’ command accomplish?

Answer 23

It forces a RSTP port to be point-to-point regardless of duplex settings.

Question 24

When running MST, all switches must have what three identical attributes to be considered in the same region?

Answer 24

The same MST configuration name, revision number, and instance-to-VLAN mapping table.

Question 25

What two STP features help detect or prevent the unexpected loss of BPDUs?

Answer 25

Loop Guard, and Unidirectional Link Detection (UDLD).

Question 26

What ports should BPDU guard never be enabled on?

Answer 26

Switch uplinks where the root bridge is located.

Question 27

Are the following configuration combinations permissible on a switch port?Root guard and Loop guard

Answer 27

NOT-Permissible!

Question 28

What happens when a BPDU is received on a port with Root Guard configured?

Answer 28

It is placed in the blocking state, with a root-inconsistent state.

Question 29

What are the 5 states a port can have after convergence in STP?

Answer 29

Root port, Designated port, Blocking port, Alternate port, and Forwarding port.

Question 30

How does UDLD work on EtherChannel ports?

Answer 30

It exchanges and echos messages on each link independently.

Question 31

In MST, by default, what VLANs are mapped to the IST (MSTI 0)?

Answer 31

All of the VLANs are mapped to the IST by default. You must explicitly map them to another MSTI if needed.

Question 32

Are the following configuration combinations permissible on a switch port?Loop Guard and UDLD

Answer 32

Permissible!

Question 33

How to other MSTIs receive BPDU information in MST?

Answer 33

The MST BPDU is sent on the IST (MSTI 0) with a special M-Record appended to the BPDU.

Question 34

What are the 2 modes of UDLD operation?

Answer 34

Normal and Aggressive.-Normal: When a unidirectional link is detected, it is still allowed to continue its operation, it marks the port as having an undetermined state, and generates a syslog message. -Aggressive: The port is placed in the errDisabled state after 8 UDLD messages sent one second apart.

Question 35

How do you globally enable Rapid Per-VLAN Spanning Tree (RPVST+)

Answer 35

(config)spanning-tree mode rapid-pvst

Question 36

According to RSTP, any port role can have what three possible states?

Answer 36

-Discarding, incoming frames are dropped, no MACs are learned.-Learning, only MACs are learned.-Forwarding, frames are forwarded according to learned frames.

Question 37

What are the 5-steps to configuring MST on a single switch?

Answer 37

1. spanning-tree mode mst2. spanning-tree mst configuration3. name NAME4. revision #####5. instance #ID# vlan #LIST#

Question 38

Where must you configure UDLD for it to work?

Answer 38

on both ends of the link.

Question 39

Can RSTP coexist on a network with CST?

Answer 39

Yes, each versions BPDUs are compatible.

Question 40

Give a quick explanation of where the following STP configurations should be used: Root guard, BPDU guard, Loop guard, UDLD.

Answer 40

-Root guard, Apply to ports where root is never expected.-BPDU guard, apply to all ports that have PortFast enabled.-Loop guard, Apply to non-designated ports, but ok to apply to all ports.-UDLD, Apply to both sides of all fiber links.

Question 41

Even though loop-guard is configured on switch ports, it action is taken on a per-_____ basis.

Answer 41

per VLAN!

Question 42

When does RSTP detect a topology change?

Answer 42

When a non-edge port transitions to the forwarding state.

Question 43

What is the default message interval for UDLD?

Answer 43

15 seconds.

Question 44

What are the three types of RSTP ports?

Answer 44

-Edge port, where only a single host connects.-Root port, has the best cost to the root.-Point-to-point, any port that connects to another switch and becomes a designated port.

Question 45

In MST, what MSTI is allowed to send BPDUs?

Answer 45

Only the IST, on MSTI 0, us allowed to send BPDUs.

Question 46

What is the IEEE standard for STP?

Answer 46

802.1D

Question 47

How does CST work out a loop-free technology with MST?

Answer 47

It considers each MST region as a single 'bridge'

Question 48

When enabled globally, what ports does UDLD effect? How do you enable it?

Answer 48

Only Fiber-Optic ports. (config)udld [enable, aggressive, message time ###]

Question 49

If a port is placed in the errDisabled state, what is the only way it can be re-enabled?

Answer 49

By being manually re-enabled, or waiting for the errDisabled timeout function.