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63 Cards in this Set
- Front
- Back
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What is the STP BPDU MAC address?
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0180.C200.0000
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What are the five 802.1D STP port states?
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Disabled
Blocking Listening Learning Forwarding |
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What is the STP Disabled port state?
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The port does not participate in STP and does not forward frames.
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Describe the STP Blocking port state.
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A non-designated port:
No Rx/Tx of data No MAC learning No Tx of BPDUs Rx of BPDUs is allowed |
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Describe the STP Listening port state.
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No Rx/Tx of data
No MAC learning Tx/Rx of BPDUs is allowed. |
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Describe the STP Learning port state.
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No Rx/Tx of data
MACs are learned Tx/Rx of BPDUs is allowed |
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Describe the STP Forwarding port state.
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Rx/Tx of data
MACs are learned Tx/Rx of BPDUs is allowed |
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What are the five 8021.D STP Port Roles?
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Root Port
Designated Port Blocking Port (Non-Designated Port) Alternate Port Forwarding Port |
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What is a Root port?
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One port on a switch that has the lowest root path cost to the Root Bridge.
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What is a Designated port?
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The port on a common network segment that has the lowest root path cost to the root bridge.
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What is an Alternate port?
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Candidate root ports but are in the Blocking state (used in UplinkFast).
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What is a superior BPDU?
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A BPDU with a better (lower) Bridge ID
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What is the Root bridge?
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A common reference point for STP computation.
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Root Bridge Placement
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Center of the Layer 2 network in the distribution layer.
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Does the STP root bridge have the highest or lowest Priority?
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Lowest
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What is the default STP bridge priority?
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32,768 or 0x8000
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If two switches bridge priority is equal, what is used as the tie-breaker?
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MAC address
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How many designated ports are there per segment?
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1
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How many root ports per switch?
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1
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What is the Root path cost?
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The cumulative cost of all the links leading to the root bridge
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How do you calculate the root path cost?
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Add the cost of the link the BPDU was received to the value in the BPDU.
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What is the range that a port's path cost can be set to?
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1 - 65,535
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Does changing a port's path cost effect the entire port or per VLAN?
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Either, depending if the "vlan" parameter is used.
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What two values make the traditional 802.1D Bridge ID?
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Bridge Priority (16 bits)
MAC Address (48 bits) |
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What two values make the 802.1t extended system ID?
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Priority (multiple of 4,096) (4 bits)
Extended System ID (VLAN ID) (12 bits) MAC Address (non-unique) (48 bits) |
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What is the multiple that an extend Bridge Priority can be?
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4096 (starting at 0)
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How is the bridge priority calculated when using the extended system id?
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Multiples of 4096 plus the VLAN number.
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When using the STP root macro, what bridge priority is the switch given when using the "primary" keyword?
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1. If the current root priority is more than 24,576 then it sets to 24,576
2. If the current root priority is less than 24,576 then it sets to 4096 less than the current value." |
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When using the STP root macro, what bridge priority is the switch given when using the "secondary" keyword?
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28,672
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What values make up a Port ID?
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Port Priority (8 bits) & Port Number (8 bits)
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What is the default Port Priority and the available range?
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Default is 128, Range is 0 - 255
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Can the port priority be changed?
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Yes
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Can the port number be changed?
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No, it is fixed.
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Is a lower or higher priority preferred?
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Lower
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Is the port priority changed per port or VLAN?
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VLAN
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What are the two types of BPUDs?
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Configuration BPDU
TCN BPDU |
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What is a Configuration BPDU?
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Used for STP computation.
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What is included in a Configuration BPDU?
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Root Bridge ID
Root Path Cost Sender Bridge ID Timer Values |
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What is a TCN BPDU?
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Used to announce changes in the network topology.
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When a port on a switch goes up or down, what type of message is sent and where is it sent to?
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TCN BPDU to its upstream router
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What happens when a root bridge receives a TCN BPUD?
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It sends a Configuration BPDU with the Topology Change (TC) flag set.
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What does a switch do when it receives a Configuration BPDU with the TC flag set?
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It shortens its bridge aging timer to the Forward Delay value (default = 15 seconds).
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What is the default BPDU Hello Time?
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2 seconds
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What is the STP Cost of a 10 Mbps link?
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100
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What is the STP Cost of a 100 Mbps link?
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19
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What is the STP Cost of a 1 Gbps link?
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4
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What is the STP Cost of a 10 Gbps link?
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2
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What are the four STP tie-breakers?
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1. Lowest root bridge ID
2. Lowest root path cost 3. Lowest sender bridge ID 4. Lowest sender port ID |
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What is Common Spanning Tree (CST)?
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IEEE 802.1D version of STP where a single instance of STP encompasses all VLANs and all BPDUs are transmitted over trunks using the native VLAN.
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What is Per-VLAN Spanning Tree (PVST)?
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Cisco-proprietary version of STP that has an instance of STP on each VLAN.
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What trunking method is needed for PVST?
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ISL
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Is PVST compatible with CST?
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No
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What is Per-VLAN Spanning Tree Plus (PVST+)?
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Cisco-proprietary version of STP that has an instance of STP on each VLAN and it interoperates with PVST and CST.
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What is the default STP Diameter?
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7 switches
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What are the steps to manually calculate STP?
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1. Identify the cost on links
2. Identify the root bridge 3. Select the root ports 4. Select the designated ports 5. Identify the blocking ports |
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What is the STP Forward Delay timer?
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Interval a switch ports spends in Listening and Learning states.
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What is the default STP Forward Delay timer?
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15 seconds
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What is the STP Hello timer?
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Interval between BPDUs.
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What is the default STP Hello timer?
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2 seconds
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What is the STP Max Age timer?
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Interval a switch stores a BPDU before discarding it.
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What is the default STP Max Age timer?
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20 seconds
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Where should the STP timers be configured?
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The root brigde.
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What IEEE spec is STP?
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802.1D
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