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- CCNA Routing and Switching 200-105
11.
Which of the following RSTP port states have the same name and purpose as a port
state in traditional 802.1D STP? (Choose two answers.)
- A.Blocking
- B.Forwarding
- C.Listening
- D.Learning
- E.Discarding
- Answer & Explanation
- Report
Answer : [B and D]
Explanation :
Explanation :
| RSTP uses port states forwarding, learning, and discarding. Forwarding and learning perform the same functions as the port states used by traditional 802.1D STP. |
12.
RSTP adds some concepts to STP that enable ports to be used for a role if another
port on the same switch fails. Which of the following statements correctly describe a
port role that is waiting to take over for another port role? (Choose two answers.)
- A.An alternate port waits to become a root port.
- B.A backup port waits to become a root port
- C.An alternate port waits to become a designated port.
- D.A backup port waits to become a designated port.
- Answer & Explanation
- Report
Answer : [A],[D]
Explanation :
Explanation :
| With RSTP, an alternate port is an alternate to the root port when a switch’s root port fails. A backup port takes over for a designated port if the designated port fails. |
13.
What STP feature causes an interface to be placed in the forwarding state as soon as
the interface is physically active?
- A.STP
- B.EtherChannel
- C.Root Guard
- D.PortFast
- Answer & Explanation
- Report
Answer : [D]
Explanation :
Explanation :
|
The PortFast feature allows STP to move a port from blocking to forwarding, without going through the interim listening and learning states. STP allows this exception
when the link is known to have no switch on the other end of the link, removing the
risk of a switching loop. BPDU Guard is a common feature to use at the same time as PortFast, because it watches for incoming bridge protocol data units (BPDU), which should not happen on an access port, and prevents the loops from a rogue switch by disabling the port. |
14.
On a 2960 switch, which of the following commands change the value of the bridge
ID? (Choose two answers.)
- A.spanning-tree bridge-id value
- B.spanning-tree vlan vlan-number root {primary | secondary}
- C.spanning-tree vlan vlan-number priority value
- D.set spanning-tree priority value
- Answer & Explanation
- Report
Answer : [B][C]
Explanation :
Explanation :
| You cannot set the system ID part of the bridge ID (BID). However, you can set the priority part of the BID, the first 16 bits, in two ways. One way sets it directly (spanning-tree vlan priority), whereas the other tells the switch to figure out a priority setting that either makes the switch root (spanning-tree root primary) or the backup (spanning-tree root secondary). |
15.
Examine the following extract from the show spanning-tree command on a Cisco
switch:
Bridge ID Priority 32771 (priority 32768 sys-id-ext 3) Address 0019.e86a.6f80Which of the following answers is true about the switch on which this command output was gathered?
- A.The information is about the STP instance for VLAN 1.
- B.The information is about the STP instance for VLAN 3.
- C.The command output confi rms that this switch cannot possibly be the root switch.
- D.The command output confi rms that this switch is currently the root switch.
- Answer & Explanation
- Report
Answer : [B]
Explanation :
Explanation :
| Cisco switches use the extended system ID format for BIDs by default, in which the priority field is broken down into a base priority value (32,768 in this case) plus the VLAN ID. The priority of this switch allows it to be capable of being the root switch, but the command output does not supply enough information to know whether this switch is currently root. |
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