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CCNA > CCNA Layer 2 > Flashcards

CCNA Layer 2 Flashcards

1
Q

802.3 defines what?

A

Ethernet

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2
Q

The “T” in ethernet standards (e.g. 1000Base-T) indicates what?

A

Twisted pair (copper)

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3
Q

What is the defining characteristic of a crossover cable?

A

Pins 1 and 2 connect to pins 3 and 6

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4
Q

What devices send over pins 1 and 2?

A

Routers, WAPs, and PC NICs

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5
Q

What devices send over pins 3 and 6?

A

Hubs and switches

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6
Q

Which fiber type can go longer distances?

A

Single mode

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7
Q

Which fiber type (single/multimode) is cheaper?

A

Multimode

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8
Q

Describe the ethernet FCS field.

A

4 bytes, in the trailer, used for error detection (not recovery)

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9
Q

How many bytes in a MAC address?

A

48 bytes

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10
Q

The original 802.3 standard describes what physical connection?

A

10Mbps ethernet over copper, 100m (10BASE-T)

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11
Q

The 802.3u standard describes what?

A

Fast ethernet, 100Mbps, 100BASE-T, 100m over copper

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12
Q

The 802.3z standard describes what?

A

Gigabit ethernet, 1000BASE-LX, 1000Mbps, 5000m over fiber

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13
Q

The 802.3ab standard describes what?

A

Gigabit ethernet, 1000BASE-T, 1000Mbps, 100m over copper

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14
Q

The 802.3an standard describes what?

A

10Gig ethernet, 10GBASE-T, 10Gbps, 100m over copper

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15
Q

List three types of pluggable ethernet transceivers.

A

Gigabit Ethernet Interface Converter (GBIC)
Small Form Pluggable (SPF), up to 1Gb
SPF+, up to 10Gb

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16
Q

What Cisco feature can compensate for the wrong type of cable?

A

auto-mdix

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17
Q

What light source is used in multimode fiber?

A

LED

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18
Q

What light source is used in single-mode fiber?

A

Laser

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19
Q

10GBASE-S defines what cable type and max distance?

A

MM, 400m

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20
Q

10GBASE-LX4 defines what cable type and max distance?

A

MM, 300m

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21
Q

10GBASE-LR defines what cable type and max distance?

A

SM, 10km (LR = Long Reach)

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22
Q

10GBASE-E defines what cable type and max distance?

A

SM, 30km

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23
Q

IEEE defines the “universal address” as what?

A

The universal uniqueness of the MAC address

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24
Q

In the ethernet header, how is IPv4 identified?

A

type 0800

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25
Q

In the ethernet header, how is IPv6 identified?

26
Q

What field does Cisco add to the HDLC header and what does it do?

A

“Type,” and it indicates what L3 protocol is being used

27
Q

Name two L2 WAN protocols.

A

HDLC and PPP

28
Q

What is the max cable length of 1000BASE-ZX?

29
Q

List the four types of memory in a Cisco device and their functions.

A

RAM: running config and real-time data
ROM: bootstrap
Flash: IOS
NVRAM: startup config

30
Q

By default, MAC addresses are aged out after how many seconds?

A

300 seconds

31
Q

A MAC address table has space for about how many entries?

32
Q

What is 802.1Q?

A

VLAN trunking protocol

33
Q

802.1Q can support how many VLANs?

A

4096 (really 4094)

34
Q

What are the “normal” and “extended” ranges for VLANs?

A

Normal: 1 to 1005
Extended: 1006 to 4094

35
Q

Is a tag added to frames in the native VLAN?

36
Q

What command effectively disables VTP?

A

vtp mode transparent

37
Q

DTP can be disabled at the interface with what command?

A

switchport nonegotiate

38
Q

Describe the spanning tree bridge ID

A

2 byte priority plus a mac address

39
Q

What three timers are included in a Hello BPDU?

A

Hello, MaxAge, and forward delay

40
Q

The winner of the STP election will have the highest or lowest priority?

41
Q

If a switch has multiple candidates for root port, what are the three tiebreakers?

A

1) Lowest neighbor bridge ID
2) Lowest neighbor port priority
3) Lowest neighbor internal port number

42
Q

What is the default STP cost of a 10Mbit port?

43
Q

How long is the STP max age timer by default?

A

10 times the Hello time

44
Q

What does the STP forward delay timer do?

A

After convergence, a port will change from blocking to forwarding. It will spend <forward> in listening state, then again in learning state, before switching to forwarding.</forward>

45
Q

What happens during the listening phase?

A

The switch does not forward traffic; it removes MAC addresses from which no frames are received during this time.

46
Q

What happens during the learning phase?

A

The switch does not forward traffic; it learns and keeps track of which MAC addresses are received on which ports.

47
Q

The “alternate port” is what?

A

In RSTP, the alternate port is the port used if the root port fails.

48
Q

Why does RSTP not need a listening or learning state?

A

When the root port fails, RSTP immediately flushes the MAC address cache and switches over to the alternate port.

49
Q

Where should PortFast be enabled?

A

End-user ports only

50
Q

What does BPDU Guard do?

A

Shuts down a port if a BPDU is detected (user ports primarily)

51
Q

What are the three options for per-VLAN STP?

A

1) PVST+
2) RPVST+
3) MST

52
Q

The STP system ID extension is made up from what two values?

A

The VLAN STP priority plus the VLAN number (ID).

53
Q

What two protocols can be used to negotiate creation of an EtherChannel?

A

1) Port Aggregation Protocol (PAgP) which is Cisco-proprietary
2) Link Aggregation Control Protocol (LACP) which is IEEE 802.3ad

54
Q

What are the maximum number of links in a PAgP-negotiated bundle?

55
Q

What are the maximum number of links in an LACP-negotiated bundle?

A

16, but only 8 can be active at once.

56
Q

In the channel-group command, what keywords configure PAgP?

A

desirable and auto

57
Q

In the channel-group command, what keywords configure LACP?

A

active and passive

58
Q

What command is necessary to enable layer 3 switching in a switch (e.g. 2960)?

A

sdm prefer lanbase-routing

59
Q

What command is necessary on a layer 3 switch to enable IP routing functions?

A

ip routing

60
Q

What command on a layer 3 switch moves a port out of switching mode and into routing mode?

A

no switchport

61
Q

What are the two main commands when configuring layer 3 EtherChannel?

A

1) int port-channel (global command)
2) channel-group on the interfaces

CCNA (4 decks)

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