Ccna certification Practice Tests

301

141.  D.  802.1D STP convergence takes 50 seconds to complete before the port is put into 

a state of forwarding or blocking. This is dependent on the STA, or spanning-tree 

algorithm. All of the other options are incorrect.

 142.  C.  When a computer is connected to an STP-enabled interface, the port will transition 

between blocking, listening, learning, and forwarding. The time between the states of 

blocking and forwarding is called the convergence and is 50 seconds. Spanning Tree 

PortFast operates in a forwarding, listening, learning, and then possibly blocking state. All 

of the other options are incorrect.

 143.  C.  An STP blocked port will block all frames from being forwarded. The blocking 

excludes BPDUs, which it will continue to listen for and calculate future topology 

decisions. When a port is in a blocking state, it will block all frames whether or not they 

are redundant, excluding BPDUs.

 144.  D.  RSTP has three transitions when a computer is plugged in (no loops). The transitions 

are discarding, learning, and forwarding, which allow for rapid convergence times. All of 

the other options are incorrect.

 145.  A.  RSTP has three port states: discarding, learning, and forwarding. Blocking and 

listening are both mapped to discarding in RSTP. When a port is in a state of discarding, 

it means the interface is discarding all frames except for BPDUs. A port in a learning state 

will learn incoming BPDUs to calculate redundant links. A port in a forwarding state will 

forward all packets as expected.. A backup port is a port on the same network segment as 

another port on the same switch; this allows communication from the network segment if 

the designated port fails.

 146.  D.  The new port state that RSTP has is discarding, which replaces the blocking state of 

STP. Learning in RSTP is the same as the learning state in STP. The forwarding state in 

RSTP is the same as the forwarding state in STP. The blocking state is not found in RSTP; 

it is found in STP.

 147.  D.  The command 

spanning-tree portfast entered into the interface will turn 

on PortFast mode. This will allow the interface to forward first. The command 

no 

switchport spanning-tree is incorrect. The command switchport spanning-tree 

portfast is incorrect. The command spanning-tree portfast default is incorrect.

 148.  B.  PortFast should only be configured on access links where end devices are plugged in 

because these devices will not typically create loops in the switch topology. If PortFast 

is configured on a trunk port, you have a very high risk of creating a loop if there is a 

misconfiguration on the switch being introduced. Voice ports have a lower probability of a 

network loop, but voice ports are usually connected to VoIP phones with built-in switches 

that can be looped. Designated ports are ports that are adjacent to a root port on the 

opposite switch that leads back to the root port.

 149.  B.  This command turns on PortFast globally for only access ports on the switch. This 

command should be used on access switches because end devices are connected at this 

level in the hierarchy. The command 

spanning-tree portfast default is used to 

configure PortFast globally. This command does not turn off Spanning Tree for any ports.

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