CCNP ENCOR - cap 3

A switch’s STP priority can be configured in increments of ______.

• 1

• 256

• 2048

• 4096

Answer explanation

D. A switch’s STP priority increments in values of 4096. The priority is actually added to the VLAN number as part of the advertisement. The VLAN identifier is 12 bits, which is a decimal value of 4096.

True or false: The advertised path cost includes the advertising link’s port cost as part of the configuration BPDU advertisement.

• True

• False

Answer explanation

False. The advertising path cost includes the calculate path cost but does not include the path cost of the interface from which the BPDU is being advertised.

True or false: The switch port with the lower STP port priority is more preferred.

• True

• False

Answer explanation

True. As part of the STP algorithm, when two links exist between two switches, on the upstream switch, the port with the lower port priority is preferred.

What happens to a switch port when a BPDU is received on it when BPDU guard is enabled on that port?

• A message syslog is generated, and the BPDU is filtered.

• A syslog message is not generated, and the BPDU is filtered.

• A syslog message is generated, and the port is sent back to a listening state.

• A syslog message is generated, and the port is shut down.

Answer explanation

BPDU guard generates a syslog message and shuts down an access port upon receipt of a BPDU.

Enabling root guard on a switch port does what?

• Upon receipt of an inferior BPDU, the port is shut down.

• Upon receipt of a superior BPDU, the port is shut down.

• Upon receipt of an inferior BPDU, the BPDU is filtered.

• When the root port is shut down, only authorized designated ports can become root ports.

Answer explanation

Root guard ensures that the designated port does not transition into a root port by shutting down the port upon receipt of a superior BPDU.

UDLD solves the problem of ______.

• time for Layer 2 convergence

• a cable sending traffic in only one direction

• corrupt BPDU packets

• flapping network links

Answer explanation

Unidirectional Link Detection (UDLD) solves the problem when a cable malfunctions and transmits data in only one direction.

Which one of the following commands enables the use of RSTP?

• spanning-tree mode rapid-pvst

• no spanning-tree mode pvst

• spanning-tree rstp

• None. RSTP is enabled by default.

On which standard is RSTP based?

• 802.1Q

• 802.1D

• 802.1w

• 802.1s

Which of the following is not a port state in RSTP?

• Listening

• Learning

• Discarding

• Forwarding

When a switch running RSTP receives an 802.1D BPDU, what happens?

• The BPDU is discarded or dropped.

• An ICMP message is returned.

• The switch begins to use 802.1D rules on that port.

• The switch disables RSTP.