Cisco (350-401-ENCOR) Exam Questions And Answers page 62

A Rapid-Per-VLAN Spanning Tree Plus (PVST+) switch port will pass through the following states:
-Discarding
-Learning
-Forwarding
RapidPVST combines the rapid transition of ports by Rapid Spanning Tree Protocol (RSTP) with the creation of spanning trees for each virtual LAN (VLAN) by PVST+. RSTP improves the slow transition of a Spanning Tree Protocol (STP) port to the forwarding state, thereby increasing convergence speed.
STP is used to eliminate loops in a switched network that is designed with redundant paths. There can be only one active path at any given time between any two endpoints on an Ethernet network. If multiple paths between the same two endpoints exist at the same time, switching loops can occur. STP activates and deactivates links dynamically to allow the network to respond to and reroute traffic around a failed link.
When RSTP is enabled, each port first enters the discarding state, in which a port receives bridge protocol data units (BPDUs) and directs them to the system module? however, the port neither sends BPDUs nor forwards any frames. The switch port then transitions to the learning state, in which it begins to transmit BPDUs and learn addressing information. Finally, a switch port transitions to the forwarding state, in which the switch port forwards frames. If a switch port determines at any time during the RSTP state process that a switching loop would be caused by entering the forwarding state, the switch port again enters the discarding state, in which the switch receives BPDUs and directs them to the system module but does not send BPDUs or forward frames.
STP port states are somewhat different from RSTP port states. A switch port will pass through the following STP states after a switch is turned on:
-Blocking
-Listening
-Learning
-Forwarding
When STP is enabled and a switch is turned on, each port first enters the blocking state, which is similar to the RSTP discarding state. The switch port then transitions to the listening state, in which it begins processing BPDUs as it listens for information to determine whether it should transition to the learning state. After entering the learning state, a switch port begins to transmit BPDUs and learn addressing information with which to build the switching database. Finally, a switch port transitions to the forwarding state, in which the switch port forwards frames. If a switch port determines at any time during the STP state process that a switching loop would be caused by entering the forwarding state, the switch port enters the disabled state, in which the switch receives BPDUs but does not direct them to the system module.
The primary differences between STP and RSTP are the port states and the speed of convergence. By default, STP takes 50 seconds to converge. By contrast, RSTP takes less than 10 seconds to converge.
Switch ports do not immediately enter the forwarding state when the switch is first turned on, unless PortFast is enabled on the port. PortFast enables a switch port to go directly to the forwarding state rather than pass through the normal STP or RSTP states. However, you should enable PortFast only on switch ports that are connected directly to endpoint workstations? otherwise, switching loops may occur.
Blocking and listening are valid STP port states but are not valid RSTP port states. Spanning is not a valid STP or RSTP port state.
https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24062-146.html
www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094797.shtml
https://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/72836-rapidpvst-mig-config.html

You should issue the command with a lower size parameter value to determine the largest datagram that the connection supports without fragmentation. The IP version 4 (IPv4) donotfragment bit, or DF bit, should be enabled if you want to determine the maximum transmission unit (MTU) size that a given connection supports. By default, packet fragmentation is used to enable oversized packets to traverse the network in chunks that are smaller than the configured MTU. The DF bit configures the ping command to attempt to send packets of a given size without fragmentation. By repeatedly pinging a destination device with smaller and smaller datagram sizes, you can determine the MTU.
The ping command supports the ability to modify the size of the datagram that it transmits as well as the ability to enable the DF bit, which is disabled by default. You can configure extended ping features either by issuing the ping command without parameters, which causes the ping command to display a series of configuration prompts, or by specifying parameters on the command line along with the ping command. For example, the ping 192.168.1.1 size 1500 dfbit command configures an extended ping with a destination IP address of 192.168.1.1, a datagram size of 1,500 bytes, and an enabled DF bit. On a connection with an MTU of 1,500 bytes, this ping succeeds, as shown in the following output:

Based on the output, you can determine that the ping succeeded. You can also determine that the DF bit is, indeed, enabled. However, issuing the ping 192.168.1.1 size 1501 dfbit command on the same device results in a failure, as shown in the following output:

In the output above, issuing the ping 192.168.1.1 size 1501 dfbit command results in a ping failure because the MTU is configured to 1,500 bytes and the DF bit is set. If you were to issue the same command without the dfbit parameter, the ping would succeed because the ping command is allowing the datagram to be fragmented, as shown in the following output:

You should not issue the command without the dfbit option, because this disables the DF bit and enables datagram fragmentation. Ping attempts with fragmentation enabled will succeed even if the size parameter remains larger than the configured MTU.
You should not issue the command without the size parameter. The size parameter in addition to the presence of the DF bit is what enables you to test which datagrams are larger than the MTU. Without the size parameter, the ping datagram will use its small default size of 100 bytes.
Cisco: Using the Extended ping and Extended traceroute Commands: The Extended ping Command