Spanning Tree Flashcards
802.1D
The original STP specification
802.1W
RSTP (rapid spanning tree protocol)
802.1S
MSTP (Multiple spanning tree protocol)
Ports state: The port that is in an administratively off position (shutdown)
Didabled
Port state: The switch port is enabled but the port is not forwarding any traffic to ensure a loop is not created.
Blocking
Port state: the switch port has transitioned from blocking state and can now send or receive BPDUs. It cannot forward any other data traffic.
Listening
Port state: the switch port can now modify the MAC address table with any network traffic that it receives. The port still cannot forward any other network traffic.
Learning
Port state: the switch port can forward all network traffic and can update the MAC table as expected.
Forwarding (final state)
A network port that connects to the root bridge or an upstream switch in the spanning tree topology.
Root port
A network port that receives and forwards BPDU frames to other switches.
Designated port (these ports provide devices and switches downstream connectivity)
The most important switch in a layer 2 topology
Root bridge
Does a port that is put into ErrDisabled by BPDU Guard automatically retore itself?
No.
To allow ports to come back up due to specific problem i.e. BPDU guard, what can you do?
You can use error recovery services to reduce overhead. EX: errdisable recovery cause bpduguard.
What is BPDU guard?
is a safety mechanism that places ports configured with STP portfast into an ErrDisabled state upon receipt of a BPDU. This ensures that a loop cannot accidentally be created if an unauthorized switch is added to a topology.
What is BPDU filter?
Simply blocks BPDUs from being transmitted out a port.
What is STP Loop guard?
prevents any alternative or root ports from becoming designated ports.
Should Loop Guard be enabled on port-fast ports?
No. (because it directly conflicts with the root/alternate port logic).
What is UDLD?
(Unidirectional Link Detection) Purpose: UDLD is a Cisco proprietary protocol used to detect and prevent unidirectional links in a network. A unidirectional link occurs when traffic is only flowing in one direction between two devices due to a physical issue, such as a faulty fiber optic cable or a misconfigured link.
Which of the following issues does MST solve? (Choose two.)
A. Enables traffic load balancing for specific VLANs
B. Reduces the CPU and memory resources needed for environments with large numbers of VLANs
C. Overcomes MAC address table scaling limitations for environments with large numbers of devices
D. Detects issues with cabling that transmits data in one direction
E. Prevents unauthorized switches from attaching to the Layer 2 domain
A. Enables traffic load balancing for specific VLANs
B. Reduces the CPU and memory resources needed for environments with large numbers of VLANs
With MST, VLANs are directly associated with ______.
A. areas
B. regions
C. instances
D. switches
C. instances
What do CST and 802.1D have in common?
A. They support only one topology.
B. They support multiple topologies.
C. They allow for load balancing of traffic across different VLANs.
D. They provide switch authentication so that inter-switch connectivity can occur.
A. They support only one topology.
True or false: The MST root bridge advertises the VLAN-to-instance mappings to all other MST switches.
False
True or false: The MST configuration version is locally significant.
False
True or false: The MST topology can be tuned for root bridge placement, just like PVST+ and RSTP.
True
MST regions can interact with PVST+/RSTP in which of the following ways? (Choose two.)
A. The MST region is the root bridge for all VLANs.
B. The MST region is the root bridge for some VLANs.
C. The PVST+/RSTP topology is the root bridge for all VLANs.
D. The PVST+/RSTP topology is the root bridge for some VLANs.
A. The MST region is the root bridge for all VLANs.
C. The PVST+/RSTP topology is the root bridge for all VLANs.
A grouping of MST switches with the same high-level configuration is known as a ________?
A. areas
B. MST region
C. instances
D. switches
B. MST region
