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35 Cards in this Set

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When using the original version of Spanning Tree Protocol (STP), what is the maximum delay that is introduced?

50 seconds

20 seconds (Max Age) + 15 seconds (Listening) + 15 seconds (Learning)

What standard defines the Spanning Tree Protocol (STP)?
802.1D
The standard that defines the Spanning Tree Protocol (STP) is IEEE 802.1D.
What version of Spanning Tree runs a separate version of 802.1D per VLAN over 802.1q trunks?
PVST+
Per VLAN Spanning Tree Plus (PVST+) is a Cisco enhancement that runs separate instances of 802.1D per VLAN on 802.1q trunks.
What version of Spanning Tree runs a separate version of 802.1w per VLAN?
PVRST+
Per VLAN Rapid Spanning Tree is a Cisco enhancement that runs separate instances of 802.1w (RSTP) per VLAN.
What standard defines the Rapid Spanning Tree Protocol (RSTP)?
802.1w
In order to speed up the convergence time of STP, RSTP (802.1w) was created.
What standard defines the Multi-Instance Spanning Tree Protocol (MSTP)?
802.1s
MSTP provides the ability to map multiple VLANs into the same Rapid Spanning Tree instance and can be done multiple times. Cisco's implementation is referred to as Multiple Spanning Tree (MST).
How many instances of RSTP are provided by MST?
16
MST provides the ability to use up to 16 separate instances of RSTP.
How many root bridges are elected when running 802.1D Spanning Tree?
One
802.1D runs one instance of STP across the entire network, and thus only one root bridge is elected.
How many root bridges are elected when running a PVRST+ Spanning Tree?
One per VLAN
PVRST+ runs one instance of 802.1w per VLAN, and a root bridge is elected per VLAN.
What port type has the best path to the root bridge?
Root port
The root port on a switch has the best path to the root switch. The only switch without a root port is the root bridge itself.
What port type receives and forwards the frames toward the root bridge?
Designated port
A designated port is typically pointed away from the root bridge and receives frames that are destined for the root bridge.
How many designated ports are allowed per segment?
One
On a Spanning Tree network, only one designated port is allowed to be on a specific segment. If multiple switches exist on a segment, an election occurs to determine which switch has the designated port.
What are the 802.1D STP port states?
Blocking, Listening, Learning, Forwarding, and Disabled
There are five STP port states used with 802.1D.

During what STP port state does the switch determine whether the port should participate in frame forwarding?

Listening

During the listening port state, the switch receives and transmits BPDUs and tries to determine whether it is safe for the switch to begin forwarding frames.

During what STP port state does the switch prepare for frame forwarding by populating the Content Addressable Memory (CAM) table?
Learning
During the learning port state, the switch is preparing to begin frame forwarding by learning the MAC addresses that are reachable (as determined by BPDUs) and entering them into the CAM table.
During what STP port state is the switch port considered part of the active STP topology?
Forwarding
When in the forwarding port state, the switch port forwards frames as normal.
During what STP port state is the port considered non-designated and does not participate in frame forwarding?
Blocking
When in the blocking port state, the port does not actively forward frames but does listen to BPDUs to maintain topology information.
What is the default Spanning Tree implementation used on Cisco switches?
PVST+
The default mode configured on Cisco switches is PVST+.

What Cisco IOS command is used to enable a switch to run in PVRST+ mode?

switch(config)#spanning-tree mode rapid-pvst

By default, a switch runs in PVST+ mode. You can switch to PVRST+ mode using the spanning-tree mode rapid-pvst command.

What Cisco IOS command would be used to force a switch to become the root bridge?

switch(config)#spanning-tree vlan vlan-id root primary

It is always a good idea to set the root bridge on the network so that the switch with the most processing power can be the center of the network.

What are the 802.1w port roles?
Root, Designated, Alternative, Backup, and Disabled
There are five 802.1w (RSTP) port roles; these differ slightly from the 802.1D roles.
Which 802.1w port role is given to a secondary path back toward the root switch, when the designated port is on another switch?
Alternative
A port that provides a secondary path back toward the root bridge, when the designated port is on another switch, is given the alternative role.
What are the 802.1w port states?
Discarding, Learning, and Forwarding
When the 802.1D is disabled, blocking and listening states all equate to the 802.1w discarding state.
What are the two link types that are available for RSTP non-edge ports?
Point-to-Point and Shared
By default, non-edge ports operating in full duplex mode are automatically configured in Point-to-Point mode, and ports operating in half duplex mode are automatically configured in Shared mode.
What Cisco IOS command would configure a switch so that all non-trunking interfaces would be configured with Portfast?
switch(config)#spanning-tree portfast default
By default, Portfast is disabled; this command would reverse this behavior.
What is the default 802.1D bridge priority?
32768
The priority values range from 0 through 65,535.
In what increments are the bridge priorities conveyed?
4096
Because the bridge priority field is only 4-bits, each increment is equal to 4096, for a range from 0 (0000) through 65,535 (1111).
What Cisco IOS command is used to enter into MST configuration mode?
switch(config)#spanning-tree mst configuration
MST works differently from the other Spanning-Tree Protocols because VLANs must be assigned to specific MST instances. This is done while in MST configuration mode.
What Cisco IOS command is used to assign VLANs to a specific MST instance?
switch(config-mst)#instance instance-id vlan vlan-id
Cisco's MST implementation allows a total of 16 separate MST instances.
What Cisco IOS command is used to force a switch to become the root bridge for a specific MST instance?
switch(config-mst)#spanning-tree mst instance-number root primary
This command would force a switch to become the root bridge for a specific MST instance.
What Cisco IOS command is used to display the current MST configuration?
switch#show spanning-tree mst configuration
This command is used to display the current MST configuration, including the configured MST instances and VLAN assignments.
What Cisco feature automatically transitions a port into forwarding state?
Portfast
The Portfast feature is used on access ports to bypass the listening and learning states for quicker forwarding.
What Cisco feature will automatically disable a Portfast-enabled port if a BPDU is received on it?
BPDU Guard
This feature is used as an extra protection from someone trying to add a rouge switch onto the network.
What Cisco IOS command would be used to enable the BPDU Guard feature on a specific switchport?
switch(config-if)#spanning-tree bpduguard enable
BPDU Guard, like Portfast, can be enabled globally or per switchport.
What two Cisco features can be used to prevent loops when a link becomes unidirectional?
Loop Guard and UDLD
Both Loop Guard and Unidirectional Loop Detection (UDLD) provide mechanisms to protect from loops should a link become unidirectional.