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CCNP ENCOR > OSPF concepts > Flashcards

OSPF concepts Flashcards

(58 cards)

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1
Q

Which OSPF packet is used to establish and maintain neighbor relationships?

A

Hello

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2
Q

Which OSPF packet summarizes the LSDB during adjacency formation?

A

Database Description (DBD)

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3
Q

Which OSPF packet is used to request missing LSAs?

A

Link-State Request (LSR)

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4
Q

Which OSPF packet is used to send LSAs to neighbors?

A

Link-State Update (LSU)

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5
Q

Which OSPF packet confirms receipt of LSAs?

A

Link-State Acknowledgment (LSAck)

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6
Q

What is the initial OSPF neighbor state?

A

Down

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7
Q

What OSPF neighbor state comes after receiving a Hello packet?

A

Init

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8
Q

In which OSPF state do routers exchange Hello packets and list seen neighbors?

A

Init

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9
Q

What is the OSPF 2-Way state?

A

Routers have seen each other’s Router ID; adjacency is formed for non-BDR/DR routers.

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10
Q

Which OSPF state is used for DR/BDR election?

A

2-Way

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11
Q

In which state do routers begin exchanging DBD packets?

A

ExStart

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12
Q

In which OSPF state do routers exchange LSDB summaries?

A

Exchange

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13
Q

What state follows Exchange, where routers request specific LSAs?

A

Loading

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14
Q

What is the final stable state in OSPF neighbor formation?

A

Full

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15
Q

What is OSPF LSA Type 1?

A

Router LSA – describes the router’s interfaces and neighbors.

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16
Q

What is OSPF LSA Type 2?

A

Network LSA – created by the DR for broadcast/multi-access networks.

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17
Q

What is OSPF LSA Type 3?

A

Summary LSA – used by ABRs to describe inter-area routes.

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18
Q

What is OSPF LSA Type 4?

A

ASBR Summary LSA – generated by ABRs to describe ASBRs.

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19
Q

What is OSPF LSA Type 5?

A

External LSA – describes routes redistributed into OSPF.

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20
Q

What is OSPF LSA Type 7?

A

NSSA External LSA – used in NSSA areas for external routes.

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21
Q

Which router generates Type 1 LSAs?

A

All routers in an OSPF area.

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22
Q

Which router generates Type 2 LSAs?

A

Only the DR on multi-access networks.

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23
Q

Which router generates Type 3 and 4 LSAs?

A

Area Border Routers (ABRs)

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24
Q

Which router generates Type 5 LSAs?

Study These Flashcards
A

Autonomous System Boundary Routers (ASBRs)

25
What is a backbone area in OSPF?
Area 0 – all other areas must connect to it.
26
What is a stub area?
An area that blocks Type 5 LSAs and uses a default route.
27
What is a totally stubby area?
Blocks Type 3, 4, and 5 LSAs; only allows intra-area and default routes.
28
What is a NSSA?
Not-So-Stubby Area – allows redistribution but blocks Type 5 LSAs.
29
What is a Totally NSSA?
Blocks Type 3, 4, and 5 LSAs; allows Type 7 LSAs with redistribution.
30
Which OSPF network types perform DR/BDR elections?
Broadcast and Non-Broadcast Multi-Access (NBMA)
31
What criteria is used to elect a DR?
Highest router priority, then highest Router ID.
32
What value disables OSPF router priority for DR election?
Priority 0
33
What command shows the DR and BDR on an interface?
`show ip ospf interface`
34
What is the LSDB?
Link-State Database – holds all LSAs received.
35
Which algorithm does OSPF use to compute the shortest path?
Dijkstra (SPF – Shortest Path First)
36
How often does OSPF refresh LSAs?
Every 30 minutes (1800 seconds)
37
What are the OSPF authentication types?
0 = None, 1 = Plaintext, 2 = MD5
38
Where is authentication configured in OSPF?
At the interface level or area level depending on type.
39
What is the default Hello interval on broadcast networks?
10 seconds
40
What is the default Dead interval on broadcast networks?
40 seconds
41
What is the default Hello interval on point-to-point links?
10 seconds
42
What is the default Dead interval on point-to-point links?
40 seconds
43
Which OSPF network type does not require DR/BDR?
Point-to-Point
44
What must be manually configured on an OSPF NBMA network?
Neighbor statements and DR/BDR manually.
45
Which OSPF network type supports broadcast and DR/BDR?
Broadcast
46
Which OSPF network type requires neighbor commands and no DR/BDR?
Point-to-Multipoint Non-Broadcast
47
What is the OSPF administrative distance?
110
48
Which OSPF version is used for IPv6?
OSPFv3
49
What is the multicast address for OSPF Hello packets?
224.0.0.5
50
What is the multicast address for OSPF DR/BDR communication?
224.0.0.6
51
What command displays the OSPF database?
`show ip ospf database`
52
What command displays OSPF neighbors?
`show ip ospf neighbor`
53
What command shows OSPF routing information?
`show ip route ospf`
54
What does the 'FULL/DR' neighbor state mean?
Neighbor relationship is fully established with the DR.
55
What command shows OSPF interfaces and their states?
`show ip ospf interface`
56
What is the purpose of the Options field in Hello packets?
To indicate capabilities such as external routing or demand circuits.
57
What field must match between routers to form an OSPF neighbor relationship?
Hello/dead interval, Area ID, authentication, subnet, and stub flags.
58
What causes OSPF to form a new adjacency?
New neighbor detected or configuration/timer change.

CCNP ENCOR (2 decks)

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