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47 Cards in this Set
- Front
- Back
What three STP methods can be used to improve convergence?
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PortFast
UplinkFast BackboneFast |
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Where should PortFast be enabled?
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On Access-Layer nodes with ports connected to end user devices.
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Does PortFast disable STP on a port?
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No
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On ports with PortFast enabled, are STP TCNs sent when the port goes up or down?
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No
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Is PortFast configured globally or per-port?
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Either
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What is UplinkFast?
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Enables fast-uplink on an access-layer switch when dual uplinks are connected to the distribution switch.
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Where do you configure UplinkFast?
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Access switches with dual uplink ports to distribution switches.
(NEVER on a Root switch) |
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Is UplinkFast configured globally, per-port, or per-VLAN?
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Globally
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What happens when UplinkFast is triggered?
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Redundant uplink port is quickly brought up and MACs are flooded out.
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What two values are changed by UplinkFast?
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Bridge priority
Port Costs |
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What is the bridge priority set to when UplinkFast is used?
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49,152
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What are the port costs incremented by with UplinkFast?
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3,000
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What is BackboneFast?
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An STP feature that can detect an indirect link failure and shorten STP convergence time to 30 seconds by bypassing the Max Age timeout period.
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Where do you configure BackboneFast?
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All switches (due to RLQ)
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Is BackboneFast configured globally or per-port?
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Globally
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What happens when BackboneFast is triggered?
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Max Age timer is bypassed, shortening convergence time.
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What is Root Link Query (RLQ)?
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Protocol used by BackboneFast to see whether upstream switches have stable connections to the root bridge
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What two STP methods can be used to protect against unexpected BPDUs?
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Root Guard
BPDU Guard |
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What is Root Guard?
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It prevents a port from becoming the root port even if superior BPDUs are heard (basically makes the port unable to receive BPDUs but it can forward them)
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Where do you configure Root Guard?
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1. Distribution switch ports facing access switches.
2. On switch ports that should never connect to a root bridge (access ports). |
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What happens when Root Guard is triggered?
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Port is put in a "root-inconsistent" state until the BPDUs cease.
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Does Root Guard affect a port or VLAN?
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Port
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What is the Root-inconsistent port state?
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State a port will enter when configured with Root Guard and a superior BPDU is detected.
NO data Tx/Rx, listen to BPDUs only |
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What does BPDU Guard do?
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Prevents loops on ports in PortFast mode.
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What happens when BPDU Guard is triggered?
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Puts ports in PortFast mode into the "errdisable" state upon receiving a BPDU.
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Does BPDU Guard affect a port or VLAN?
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Port
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Where do you configure BPDU Guard?
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Globally or per-port.
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What two STP methods can be used to protect against the sudden loss of BPDUs?
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Loop Guard
UDLD |
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What is Loop Guard?
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Tracks BPDU activity on non-designated ports and moves it to the "loop-inconsistent" state when BPDUs stop being received.
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Where do you configure Loop Guard?
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1. Ports between distribution switches
2. Uplink ports from access to distribution switches |
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What happens when Loop Guard is triggered?
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Port is put into the "loop-inconsistent" state until BPDUs are received again.
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Does Loop Guard affect a port or VLAN?
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VLAN: but it is configured per port or globally
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What is Unidirectional Link Detection (UDLD)?
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Monitors a port to see if it is actually operating bidirectionally.
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Where do you configure UDLD?
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All switch ports (fiber ports)
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What are the two UDLD modes?
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Normal
Aggressive |
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What happens when UDLD is triggered?
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Normal mode: continued operation, event logged
Aggressive mode: errdisable state |
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What layer does UDLD operate at?
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Layer 2
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What does UDLD send to the other end of the link?
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Echos
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Does UDLD affect a port or VLAN?
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Port
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What is the default UDLD message timer?
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15 seconds
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What is UDLD Aggressive Mode?
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When UDLD condition is detected, UDLD message sent out for 8 seconds, then port is placed in the "errdisable" state.
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What is UDLD Normal Mode?
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When UDLD condition is detected, port is allowed to continue to operate and the action is logged.
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How do you block all BPDUs on a port?
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Enable BPDU filtering.
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What does BPDU filtering do?
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Prevents BPDUs from being sent or processed on a port.
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Is BDPU filtering enabled globally on all ports or per-port?
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Either
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When BPDU Filtering is configured globally, what happens to a PortFast enabled port when it receives a BPDU?
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The port immediately loses its operational PortFast status and BPDU Filtering is disabled and it resumes sending BPDUs.
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When BPDU Filtering is configured specifically for a port, what happens to a PortFast enabled port when it receives a BPDU?
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It ignores all BPDUs it receives and sends no BPDUs.
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