Chapter 4 Flashcards Preview

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Flashcards in Chapter 4 Deck (16):
1

BPDU guard

Prevents accidental connection of switching devices to portfast enabled ports - connecting switches to portfast-enabled ports can cause layer to loops

2

BPDU filtering

restricts the switch from sending unnecessary BPDUs out access ports

3

Root guard

Prevents switches connected on ports configured as access ports from becoming the root switch

4

Loop guard

Prevents root ports and alternate ports from moving to forwarding state when they stop receiving BPDUs

5

If a portfast enabled interface receives a BPDU what happens?

the interface goes into err-disable state

6

If BPDU filtering is on an interface it is the same as...

disabling spanning tree

7

Superior BPDU

are received on a root guard-enabled port the port moves to root-inconsistent STP state which is the same as the listening state

8

UDLD

unidirectional link detection

9

UDLD Normal Mode

changes the UDLD-enabled port to an undetermined state if it stops receiving UDLD messages from its directly connected neighbor

10

UDLD Aggressve Mode (preferred)

When a port stops receiving UDLD packets, UDLD tries to re-establish the connection with the neighbor, after 8 failed tries the port state changes to err-disabled

11

Flex Links

provides an alternative to STP

12

Potential STP Problems

Duplex mismatch
Unidirectional link failure
Frame corruption
Resource errors
PortFast configuration error

13

Duplex Mismatch

Point-to-point link one side is configured as full duplex and the other side is configured as half duplex

14

Unidirectional Link Failure

frequent cause of bridge loops

15

Frame Corruption

is generally a result of a duplex mismatch, bad cable, or incorrect cable length

16

Resource Errors

STP is performed by the CPU this means that if the CPU of th bridge s over-utilized it might lack the resources to send out BPDUs this is however unlikly