Chapter 10 - Ethernet Switch Troubleshooting

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CDP Port Identifier refers to the same part as __________, but it applies to the _______

Local interface

refers to the interface on the other switch which send the CDP message, rather than the interface on the local switch on which the message was recieved

CDP Platform tells?

Model and OS level running in the device

CDP address lists (data-link address/network address/both)

both (if both are available)

show cdp neighbors

one summary line of information about each neighbor
OR
just the neighbor found on a specific interface if an interface was listed

show cdp neighbors detail

one large set of information for each neighbor

show cdp entry 'name'

lists one large set of information for the named neighbor (case-sensitive)

interface configuration mode subcommand to turn off cdp on a specific interface

no cdp enable
(cdp enable turns it on)

global configuration mode command to turn off cdp for the entire switch

no cdp run
(cdp run turns it on)

interface configuration mode subcommand to set an interface's speed

speed {10|100|1000}

interface configuration mode subcommand to set an interface's duplex

duplex {half|full}

What are two 'show' commands to display the duplex and speed of an interface

show interfaces
AND
show interfaces status

T/F: both the 'show interfaces' AND the 'show interfaces status' commands will show whether duplex and speed settings were learned through autonegotiation

false (only the 'show interfaces status' will)

What is the only command to show whether speed and duplex settings were learned through autonegotiation?

'show interfaces status'

If one device is using autonegotiation and the other isn't, how are speed and duplex decided by the device using autonegotiation?

Unless the speed of the other device is known to be 1000Gbps, the device is set to half duplex.

Unless the speed of the other device is known, the speed will be set to 10Mbps

Through what process would a switch be able to determine, when using autonegotiation, the speed of a connected device which was not using autonegotiation?

If the other device has had the speed set using the 'speed' command.

If there is a duplex mismatch, the switch interface will be in what state?

connect (up/up)

What are symptoms of a duplex mismatch?

Intermittent errors

A significant problem exists if the collision counters show more than ____ of all output frames have collided

.1%

An incrementing late collisions counter typically means one of which two things?

the interface is connected to a collision domain whose cabling exceeds Ethernet cable length standards
OR
there is a duplex mismatch (one device is using half-duplex and the other is using full-duplex)

An abnormally high number of collisions will be detected by the device on which side of a duplex mismatch?

the device using half-duplex

What is are the counter values implying excessive noise and what are the likely causes?

many input errors with few collisions

causes: wrong cable category, damaged cables, EMI

What are the likely causes of an interface with an abnormally high number of collisions but not necessarily an incrementing late collision counter?

duplex mismatch, jabber, DDos

What is the definition of jabber?

When a NIC ignores Ethernet rules and sends frame after frame without a break between the frames

In order to show only the dynamically-learned MAC table entries, use what command? and what mode does the command work in?

show mac address-table dynamic

EXEC mode

MAC table entries listing "CPU" as an outgoing interface mean what

These are addresses for overhead such as CDP and STP. It means frames for these MAC addresses should be sent to the switch's CPU.

(i wonder are these also universally unique MAC addresses?)

ACL

Access Control List

Either the ______ or ______ port security violation action will cause a port to discard frames but still be in a connect (up/up) state

protect OR restrict


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