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ICND1 > Chapter 10 - Troubleshooting Ethernet LANs > Flashcards

Chapter 10 - Troubleshooting Ethernet LANs Flashcards

1
Q

What is CDP?

A

Cisco Discovery Protocol - Discovers basic information about neighboring routers and switches without needing to know the passwords for the neighboring devices.

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2
Q

What are 5 things you can learn about other Cisco devices through CDP?

A

1) Device identifier - The host name.
2) Address list - Network and data link addresses
3) Port identifier - The interface on the router or switch that sent the CDP advertisement
4) Capabilities list - What type of device it is (router or switch)
5) Platform - The model and OS level running on the device

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3
Q

What are the 3 show CDP commands that list information about neighbors?

A

1) show cdp neighbors - lists one summary line of information about each neighbor
2) Show cdp neighbors detail - lists one large set ( approximately 15 lines) of information, one set for every neighbor
3) show cdp entry {name} - lists the same information as the show cdp neighbors detail except only for the named neighbor

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4
Q

Cisco recommends that CDP be enabled on what ports connected to what types of devices?

A

For switches, any ports connected to another switch, a router, or to an IP phone.

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5
Q

What command would disable/enable CDP on an interface?

A

no cdp enable or cdp enable

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6
Q

What command would disable/enable CDP globally?

A

no cdp run or cdp run

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7
Q

What are 3 commands you could use to verify CDP operations?

A

1) show cdp - states whether CDP is enabled globally
2) show cdp interface - states whether CDP is enabled on an interface
3) show cdp traffic - lists global statistics for the # of CDP advertisements sent and received

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8
Q

What’s typically the root cause if the line status is administratively down and the protocol status is down, and the interface status is disabled?

A

The interface is configured with the shutdown command.

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9
Q

What’s typically the root cause if the line status is down and the protocol status is down, and the interface status is notconnect?

A

No cable; bad cable; wrong cable pinouts; the speeds are mismatched on the two connected devices; the device on the other end of the cable is (a) powered off, (b) shutdown, or (c) error disabled.

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10
Q

What’s typically the root cause if the line status up and the protocol status is down, and the interface status is notconnect?

A

An interface up/down state is not expected on LAN switch physical interfaces.

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11
Q

What’s typically the root cause if the line status is down and the protocol status is down (err-disabled), and the interface status is err-disabled?

A

Port security has disabled the interface.

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12
Q

What’s typically the root cause if the line status up and the protocol status is up, and the interface status is connected?

A

The interface is working.

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13
Q

Which 2 commands list both the actual speed and duplex settings on an interface?

A

show interfaces and show interfaces status commands

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14
Q

Which command actually shows how the switch determined the speed and duplex settings?

A

show interfaces status command

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15
Q

During autonegotiation, if the speed is not known through any means, what speed and duplex settings are used?

A

Speed at 10 Mbps, half-duplex

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16
Q

If the switch successfully senses the speed without IEEE autonegotiation, by just looking at the signal on the cable and the speed is 10 or 100 Mbps, what duplex setting is used?

A

half-duplex

17
Q

If the switch successfully senses the speed without IEEE autonegotiation, by just looking at the signal on the cable and the speed is 1000 Mbps, what duplex setting is used?

A

full-duplex

18
Q

Which command shows the contents of a switch’s MAC address table?

A

show mac address-table

19
Q

If you only want to see dynamically learned mac addresses in the mac address table, what command would you input?

A

show mac address-table dynamic

20
Q

What are the 2 main steps of a switch’s forwarding logic?

A

1) Process functions on the incoming interface, if the interface is currently in an up/up (connected) state.
2) Make a forwarding decision. Look for the frame’s destination MAC address in the MAC address table, but only for entries in the VLAN identified in Step 1.

21
Q

What 3 steps or logic does the switch take when processing traffic on an incoming interface?

A

A) If configured, apply port security logic to filter the frame as appropriate.
B) If the port is an access port, determine the interface’s access VLAN.
C) If the port is a trunk, determine the frame’s tagged VLAN.

22
Q

During step 2 of the switch’s forwarding logic, the switch makes a forwarding decision by looking at the frame’s destination MAC address, if the MAC address is found (unicast) in the mac address table, what does the switch do with the frame?

A

Forward the frame out the only interface listed in the matched address table entry.

23
Q

During step 2 of the switch’s forwarding logic, the switch makes a forwarding decision by looking at the frame’s destination MAC address, if the MAC address is not found (unicast) in the mac address table, what does the switch do with the frame?

A

Floods the frame out all other access ports (except the incoming port) in that same VLAN, plus out trunks that have not restricted the VLAN from that trunk.

24
Q

During step 2 of the switch’s forwarding logic, the switch makes a forwarding decision by looking at the frame’s destination MAC address, if the MAC address is a broadcast, what does the switch do with the frame?

A

Floods the frame out all other access ports (except the incoming port) in that same VLAN, plus out trunks that have not restricted the VLAN from that trunk.

25
Q

What command is very useful when troubleshooting frames discarded because of port-security?

A

show port-security interface

26
Q

What 2 EXEC command lists each VLAN and all interfaces assigned to that VLAN (but does not include operational trunks)?

A

show vlan brief and show vlan

27
Q

What EXEC command lists both access and trunk ports in the VLAN?

A

show vlan id {num}

28
Q

Which EXEC command identifies the interface’s access VLAN and voice VLAN, plus the configured and operational mode (access or trunk)?

A

show interfaces {type number} switchport

29
Q

Which EXEC command lists MAC table entries, including the associated VLAN?

A

show mac address-table

30
Q

How does a switch treat a VLAN if the VLAN is shutdown?

A

It disables the VLAN on that switch only, so that the switch will not forward frames in that VLAN.

31
Q

Which command would help determine whether a VLAN is allowed on a trunk?

A

show interfaces trunk

ICND1 (18 decks)

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