Ccna certification Practice Tests

299

 127.  B.  The switch with the MAC address of 0011.03ae.d8aa will become the root bridge. Its 

MAC address is the lowest of the four switches. All of the other options are incorrect.

 128.  D.  All Cisco switches are defaulted to the Cisco proprietary STP protocol extension of 

Rapid PVST+. 802.1D is the original IEEE specification for STP. 802.1w is the IEEE 

specification for RSTP. PVST+ is the Cisco proprietary protocol extension for STP.

 129.  D.  An alternate port is a port that is in a discarding state. If the root port fails on the 

switch with the alternate port, then the alternate port becomes the root port for that 

switch. An alternate port is used only if the root bridge fails; it will not allow for an 

alternate path on a non-root bridge. An alternate port cannot replace a designated port if 

it fails. An alternate port is never placed in a forwarding state.

D

RP

AP

RP

D

D

BPDUs

D

RP

RP

D

D

Failed

130.  C.  The root bridge is elected by all of the switches and has the lowest MAC address and 

priority of all the switches in the network. The root bridge is not elected based upon a 

high or low IP address. Spanning Tree can function without an IP address, since it is a 

layer 2 loop avoidance.

 131.  A.  The root bridge is a point of perspective for the rest of the STP network. It is important 

to have a point of perspective to calculate which ports are blocked and which remain in a 

forwarding mode. The root bridge has no influence on the forwarding decisions of frames. 

Each switch is responsible for its own calculation of STP; only the root bridge election is 

the consensus of all switches in the network.

 132.  C.  The bridge ID is made up of a 2-byte bridge priority and a 6-byte MAC address for a 

total of 8 bytes. All of the other options are incorrect.

 133.  A.  A designated port is a port that has the lowest cost compared to the higher cost of the 

redundant ports. It is placed into a forwarding state for a network segment. A designated 

port is determined to have the lowest cost, and not the highest cost, when it is placed into 

a forwarding state. A port that has the lowest cost to the root bridge is a root port and 

not a designated port. A port that has the highest cost to the root bridge is placed into a 

blocking state.

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