Chapter 3: Advanced STP Tuning Flashcards
Ideal root bridge placement is located on a _______ switch?
A. Core
B. Distribution
C. Access
Core
What ensures that a switch is chosen as the root bridge?
Lowering the priority to 0.
What command is used to modify spanning tree priority?
spanning-tree vlan [vlan id] priority [#]
What command executes a script that modifies STP priority?
spanning-tree vlan [#] root {primary|secondary}
What is the spanning-tree vlan priority range?
0-61440 in increments of 4096
spanning-tree vlan [#] root primary modifies the vlan priority to what vlaue?
24576
spanning-tree vlan [#] root secondary modifies the vlan priority to what vlaue?
28672
What command is used to change STP port cost for a specific vlan?
spanning tree [vlan #] cost [#]
Places a port in the ErrDisabled state if a superior BPDU is received on a configured port.
Root Guard.
What STP feature is used to disable TCN generation on access ports?
Portfast
Causes a port to begin forwarding traffic immediately.
Portfast
What happens if a BPDU is received on a portfast-enabled port?
Portfast is removed from the port.
True or False:
Portfast can only be enabled in interface configuration mode.
False.
Portfast can be enabled globally or on a port-by-port basis.
In what scenario can a trunk port have portfast enabled?
When the port is connected to a single host.
ex. server with one NIC running a hypervisor with VMs on different VLANs.
What is the command to enable portfast on all access ports?
spanning-tree portfast default
What STP feature shuts down portfast-enabled ports if a BPDU is received?
BPDU guard
By default, does a port that is put in the ErrDisable state by BPDU guard automatically restore itself?
No.
What command is used to automatically restore a port placed in the ErrDisable state by BPDU guard?
errdisable recovery cause bpduguard
Default Error Recovery service time
300 seconds
This STP feature blocks BPDUs from being sent/received on a port.
BPDU filter
BPDU guard global config command.
BPDU guard interface config command.
BPDU guard global config command #spanning-tree portfast bpduguard default
BPDU guard interface config command.
#spanning-tree bpduguard {enable | disable}
Prevents alternative or root ports from becoming designated ports due to loss of BPDUs on the root port.
Loop guard
Places a port in ErrDisabled state while BPDUs are not being received.
Loop guard
What mode is loop guard configured?
global config
