Volume 1 - Chapter 10: RSTP and EtherChannel Configuration Flashcards
What is the primary reason for using PVST to create a different topology for different VLANs?
For load balancing. Traffic for one VLAN goes over one link, while another VLAN’s traffic goes over a different link.
Which version of spanning-tree was created by Cisco
PVST+
What is the IEEE standard for MSTP?
802.1s as an amendment to 802.1Q.
Which later version of STP was a non-Cisco version?
MSTP.
What is the global command to tell a switch to use PVST+?
spanning-tree mode pvst
What is the command to tell the switch to use RSTP?
Technically does not exist. Only the Per VLAN version of Rapid STP is supported
spanning-tree mode rapid-pvst
What is the global command to tell the switch to use MSTP?
spanning-tree mode mst
Describe how the BID differs in PVST+.
In PVST+, the priority field is modified to include a System ID extension subfield.
What size is the System ID subfield used in PVST+?
12 bits.
What value is represented by the System ID Extension subfield used in PVST+?
It refers to the VLAN ID.
What is the range of values for the priority field of a BPDU on a switch utilizing STP?
0 to 65,535
What is the command to set the spanning tree priority for a specific VLAN in PVST+?
spanning-tree vlan vlannumber priority prioritynumber
What is the size of the configured priority of a PVST+ BID?
4 bits
What is the correct order and size of a PVST BID?
BID Priority is 2 bytes, consisting of the following:
- Priority: 4 bits
- System ID Extension: 12 bits
Followed by the System ID, which is 6 bytes
Total BID size is 8 bytes
What is the command to set a switch to act as the root primary?
spanning-tree vlan x root primary
What is the command to set a switch to act as the root secondary?
spanning-tree vlan x root secondary
How does a switch become the root primary when using the following command:
spanning-tree vlan x root primary
By choosing a priority of 24,576 or 4096 lower than the current root switch
How does a switch become the root secondary when using the following command:
spanning-tree vlan x root secondary
By choosing a priority of 28,672
Which multicast address do switches utilizing RSTP send to as per IEEE?
0180.C200.0000
Which multicast address do switches utilizing RPVST+ send to as per IEEE?
0100.0CCC.CCCD
What VLAN does RSTP send its BPDU messages out by default?
The currently configured native VLAN, and without a VLAN tag.
What is the system ID extension used by RSTP in the BID?
0000.0000.0000 since RSTP does not create a tree for each VLAN.
What is the command to enable the use of PortFast on a switchport?
spanning-tree portfast
What is the command to enable the use of BPDU Guard on a switchport?
spanning-tree bpduguard enable
What must be done to re-enable an interface that has been put into err-disable after trigging BPDU Guard
Shutdown, then no shutdown
Which commands are used to apply PortFast logic to an interface but only in the port operates as an access port or trunk?
For access interfaces:
spanning-tree portfast
For trunk interfaces:
spanning-tree portfast trunk
When running the command “show spanning-tree”, interface Gi0/1 shows the “Type” as P2p.
What does this detail indicate about the interface’s operation?
That the interface is not configured to use PortFast logic.
When running the command “show spanning-tree”, interface Gi0/1 shows the “Type” as P2p Edge.
What does this detail indicate about the interface’s operation?
That the interface is configured to use PortFast logic.
What is the command to enable PortFast on all access-interfaces by default?
spanning-tree portfast default
When PortFast is enabled globally across the switch’s access interfaces, what is the command to disable the use of PortFast on a specific interface?
In interface configuration mode:
spanning-tree portfast disable
What is the command to enable BPDU Guard on all access-interfaces by default?
spanning-tree bpduguard default
When BPDU guard is enabled globally across the switch’s access interfaces, what is the command to disable the use of BPDU Guard on a specific interface?
In interface configuration mode:
spanning-tree bpduguard disable
What is the command to enable BPDU Guard on all PortFast-enabled interfaces by default?
spanning-tree portfast bpduguard default
What is the command to enable BPDU Filter on all PortFast-enabled interfaces by default?
spanning-tree portfast bpdufilter default
When BPDU Filter is enabled globally across the switch’s access interfaces, what is the command to disable the use of BPDU Filter on a specific interface?
spanning-tree bpdufilter disable
What command is used to filter incoming and outgoing BPDUs on an interface?
spanning-tree bpdufilter enable
What is the command to enable the use of Root Guard for a specific interface?
spanning-tree guard root
What happens to a Root Guard enabled interface when it receives a superior hello?
STP puts the port into a Broken state (BRK) and discards all traffic.
When running the command “show spanning-tree”, interface Gi0/1 shows the “Type” as P2p *Root_Inc.
What does this detail indicate about the interface’s operation?
That the port has been put into a BRK state due to triggering Root Guard.
What is the command to enable Loop Guard by default across all P2P switch ports?
spanning-tree loopguard default
What is the command to enable the use of Loop Guard on a specific interface?
spanning-tree guard loop
What is the command to disable the use of Loop Guard on a specific interface?
no spanning-tree guard loop
What is the interface subcommand to set a port into a static EtherChannel?
channel-group # mode on
What is the command to show information about a specific EtherChannel interface?
show interface channel-group #
What is the command to show information about all EtherChannel interfaces?
show etherchannel
or show etherchannel summary
What are the original and current IEEE standards for LACP?
Originally: 802.3ad
Current: 802.1AX
What is the maximum support amount of physical interfaces in a LACP channel?
16
What is the maximum support amount of physical interfaces in a PAgP channel?
8 active interfaces, with 8 additionally on standby
What are the commands to assign an interface to a PAgP EtherChannel?
In interface configuration mode:
channel-group # mode auto
channel-group # mode desirable
What are the commands to assign an interface to a LACP EtherChannel?
In interface configuration mode:
channel-group # mode active
channel-group # mode passive
A technician configures 2 interfaces into an EtherChannel using the following commands:
Switch 1 | Ports Gi1/0/1-2
channel-group 10 mode passive
Switch 2 | Ports Gi1/0/1-2
channel-group 10 mode passive
What type of EtherChannel will be formed by this configuration?
An EtherChannel will not be formed. The technician is trying to configure an LACP channel, but at least one side of the channel must be configured to use active
A technician configures 2 interfaces into an EtherChannel using the following commands:
Switch 1 | Ports Gi1/0/1-2
channel-group 10 mode active
Switch 2 | Ports Gi1/0/1-2
channel-group 10 mode passive
What type of EtherChannel will be formed by this configuration?
A LACP EtherChannel will be formed
A technician configures 2 interfaces into an EtherChannel using the following commands:
Switch 1 | Ports Gi1/0/1-2
channel-group 10 mode auto
Switch 2 | Ports Gi1/0/1-2
channel-group 10 mode desirable
What type of EtherChannel will be formed by this configuration?
A PAgP EtherChannel will be formed
A technician configures 2 interfaces into an EtherChannel using the following commands:
Switch 1 | Ports Gi1/0/1-2
channel-group 10 mode auto
Switch 2 | Ports Gi1/0/1-2
channel-group 10 mode auto
What type of EtherChannel will be formed by this configuration?
An EtherChannel will not be formed. The technician is trying to configure an PAgP channel, but at least one side of the channel must be configured to use desirable
A technician configures 2 interfaces into an EtherChannel using the following commands:
Switch 1 | Ports Gi1/0/1-2
channel-group 10 mode active
Switch 2 | Ports Gi1/0/1-2
channel-group 10 mode desirable
What type of EtherChannel will be formed by this configuration?
An EtherChannel will not be formed. One side of the channel is configured to use LACP with the active command, the other side is configured to use PAgP with the desirable command.
What interface configurations must be identical on both ends of a switch-to-switch link in order for a successful EtherChannel to form?
Speed
Duplex
Port Mode: Access or Trunk
If using access; the assigned VLAN
If using trunk; the allowed VLAN list
If using trunk; the native VLAN
What is the command to set the EtherChannel load-balancing method?
port-channel load-balance method
What are the configurable methods for loading balancing?
src-mac
dst-mac
src-dst-mac
src-ip
dst-ip
src-dst-ip
src-port
dst-port
src-dst-port