ENCOR-Cap 2

How many different BPDU types are there?

• 1

• 2

• 3

• 4

Answer explanation

There are two BPDU types: the configuration BPDU and topology change notification BPDU.

What attributes are used to elect a root bridge?

• Switch port priority

• Bridge priority

• Switch serial number

• Path cost

• Bridge MAC address

Answer explanation

The switch with the lowest bridge priority is elected as the root bridge. In the event of a tie, the bridge MAC address is used to elect a root bridge.

The original 802.1D specification assigns what value to a 1 Gbps interface?

• 1

• 2

• 4

• 19

Answer explanation

The original 802.1D specification set the value of 4 for a 1 Gbps interface.

All of the ports on a root bridge are assigned what role?

• Root port

• Designated port

• Superior port

• Master port

Answer explanation

All of the ports on a root bridge are assigned the designated port role (forwarding).

Using default settings, how long does a port stay in the listening state?

• 2 s

• 5 s

• 10 s

• 15 s

Answer explanation

The default 802.1D specification places a switch port in the listening state for 15 seconds.

Upon receipt of a configuration BPDU with the topology change flag set, how do the downstream switches react?

• By moving all ports to a blocking state on all switches

• By flushing out all MAC addresses from the MAC address table

• By temporarily moving all non-root ports to a listening state

• By flushing out all old MAC addresses from the MAC address table

• By updating the Topology Change version flag on the local switch database

Answer explanation

Upon receipt of a TCN BPDU, a switch sets the age for all MAC addresses to 15 seconds. Non-active/older entries are flushed from the MAC address table.

Which of the following is not an RSTP port state?

• Blocking

• Listening

• Learning

• Forwarding

Answer explanation

The blocking and listening states have been combined into the discarding state of RSTP.

True or false: In a large Layer 2 switch topology, the infrastructure must fully converge before any packets can be forwarded.

• True

• False

Answer explanation

STP allows for traffic to flow between switches once a root bridge has been elected and the ports have gone through the appropriate listening and learning stages.

True or false: In a large Layer 2 switch topology that is running RSTP, the infrastructure must fully converge before any packets can be forwarded.

• True

• False

Answer explanation

RSTP allows for traffic to flow between switches that have synchronized with each other, while other parts of the Layer 2 topology converge.