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CCNA Layer 2 Flashcards

(78 cards)

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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 copper 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
In the ethernet header, how is IPv6 identified?
type 86DD
26
What field does Cisco add to the HDLC header and what does it do?
"Type," and it indicates what L3 protocol is being used
27
Name two L2 WAN protocols.
HDLC and PPP
28
What is the max cable length of 1000BASE-ZX?
70km
29
List the four types of memory in a Cisco device and their functions.
RAM: running config and real-time data ROM: bootstrap Flash: IOS NVRAM: startup config
30
By default, MAC addresses are aged out after how many seconds?
300 seconds
31
A MAC address table has space for about how many entries?
8000
32
What is 802.1Q?
VLAN tagging protocol
33
802.1Q can support how many VLANs?
4096 (really 4094)
34
What are the "normal" and "extended" ranges for VLANs?
Normal: 1 to 1005 Extended: 1006 to 4094
35
Is a tag added to frames in the native VLAN?
No
36
What command effectively disables VTP?
vtp mode transparent
37
DTP can be disabled at the interface with what command?
switchport nonegotiate
38
Describe the spanning tree bridge ID
2 byte priority plus a mac address
39
What three timers are included in a Hello BPDU?
Hello, MaxAge, and forward delay
40
The winner of the STP election will have the highest or lowest priority?
Lowest
41
If a switch has multiple candidates for root port, what are the three tiebreakers?
1) Lowest neighbor bridge ID 2) Lowest neighbor port priority 3) Lowest neighbor internal port number
42
What is the default STP cost of a 10Mbit port?
2,000,000
43
How long is the STP max age timer by default?
10 times the Hello time
44
What does the STP forward delay timer do?
After convergence, a port will change from blocking to forwarding. It will spend in listening state, then again in learning state, before switching to forwarding.
45
What happens during the listening phase?
The switch does not forward traffic; it removes MAC addresses from which no frames are received during this time.
46
What happens during the learning phase?
The switch does not forward traffic; it learns and keeps track of which MAC addresses are received on which ports.
47
The "alternate port" is what?
In RSTP, the alternate port is the port used if the root port fails.
48
Why does RSTP not need a listening or learning state?
When the root port fails, RSTP immediately flushes the MAC address cache and switches over to the alternate port.
49
Where should PortFast be enabled?
End-user ports only
50
What does BPDU Guard do?
Shuts down a port if a BPDU is detected (user ports primarily)
51
What are the three options for per-VLAN STP?
1) PVST+ 2) RPVST+ 3) MST
52
The STP system ID extension is made up from what two values?
The VLAN STP priority plus the VLAN number (ID).
53
What two protocols can be used to negotiate creation of an EtherChannel?
1) Port Aggregation Protocol (PAgP) which is Cisco-proprietary 2) Link Aggregation Control Protocol (LACP) which is IEEE 802.3ad
54
What are the maximum number of links in a PAgP-negotiated bundle?
8
55
What are the maximum number of links in an LACP-negotiated bundle?
16, but only 8 can be active at once.
56
In the channel-group command, what keywords configure PAgP?
desirable and auto
57
In the channel-group command, what keywords configure LACP?
active and passive
58
What command is necessary to enable layer 3 switching in a switch (e.g. 2960)?
sdm prefer lanbase-routing
59
What command is necessary on a layer 3 switch to enable IP routing functions?
ip routing
60
What command on a layer 3 switch moves a port out of switching mode and into routing mode?
no switchport
61
What are the two main commands when configuring layer 3 EtherChannel?
1) int port-channel (global command) 2) channel-group on the interfaces
62
What VLAN numbers cannot be deleted but also cannot be used?
1002-1005
63
List two global commands to disable VTP.
1) vtp mode transparent 2) vtp mode off
64
What interface command configures a voice VLAN?
switchport voice vlan (vlanID)
65
What command limits which VLANs can be sent over a trunk?
switchport trunk allowed vlan
66
What command configures the native VLAN on a trunk interface?
switchport trunk native vlan (vlanID)
67
What does RSTP call the blocking state?
discarding state
68
In STP, MaxAge is 10 times the Hello time. In RSTP, MaxAge is ___ times the Hello time.
3
69
In RSTP, what is an alternate port?
A port that can be used as a root port if the original root port fails.
70
In RSTP, what is a backup port?
A port that can be used as a designated port if the original designated port fails.
71
True or false: RSTP does not use a listening state.
True
72
Explain BPDU Guard.
When enabled on a port with PortFast, if a BPDU is received, BPDU Guard shuts down the port.
73
Explain BPDU Filter.
When enabled on a port with PortFast, if a BPDU is received, PortFast is disabled, and regular STP is run.
74
Root Guard is best used when...
switches you control connect to switches you do not control.
75
When Root Guard blocks a port, it is called...
broken
76
Root Guard works by...
Blocking ports when a superior BPDU is received from a switch that you do not want to be root
77
What type of links is Loop Guard designed for?
fiber
78
Spanning-tree ports can be configured as P2P or Shared. What port setting does this really reflect?
Whether the port is full-duplex (P2P) or half-duplex (shared).

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