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CCNP Route > OSPF LSAs > Flashcards

OSPF LSAs Flashcards

1
Q

Name the six IPv4 LSA types.

A

1 - router, 2 - network, 3 - network summary, 4 - ASBR summary, 5 - AS external, 7 - NSSA external

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2
Q

What type of OSPF packet contains LSAs?

A

Link State Update (LSU)

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3
Q

What information does a type 1 LSA contain and where is it shared?

A

A type 1 router LSA contains all the information about a router’s attached links and is flooded to all routers in the area.

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4
Q

What value is used for the link state identifier (LSID) field in type 1 advertisements?

A

Type 1 router LSAs use the source router’s router-id in the link state id field.

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5
Q

Give the command for showing all type 1 LSAs from router 1.1.1.1.

A

sh ip ospf database router adv-router 1.1.1.1

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6
Q

As a rule of thumb, areas should contain no more than what number of routers?

A

40

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7
Q

What four types are advertised in type 1 LSAs?

A

Type 1 router LSAs can be “stub,” “transit network”, “another router (point-to-point)” or virtual links.

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8
Q

What are in the link id and link data fields for a “stub” network in a type 1 router LSA?

A

Link id: network

Link data: netmask of the interface

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9
Q

What are in the link id and link data fields for a “transit network” in a type 1 router LSA?

A

Link id: DR’s IP address

Link data: router’s IP address on the link

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10
Q

What are the link id and link data fields for a “router (point-to-point)” network in a type 1 router LSA?

A

Link id: neighboring router ID
Link data: router’s IP address on the link

Then, a second entry is appended, using the same link but as a stub network.
Link id: network
Link data: netmask of the interface

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11
Q

What are the link id and link data fields for a “virtual link” network in a type 1 router LSA?

A

Link id: neighboring router ID

Link data: router’s IP address on the link

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12
Q

How are point-to-multipoint and loopback IP addresses advertised?

A

As /32 host addresses

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13
Q

What is the maximum amount of time an LSA remains valid?

A

1 hour (3,600 seconds)

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14
Q

How is information poisoned in OSPF?

A

By sending an LSA with the age set to the maximum time

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15
Q

Which links are advertised as /32 host addresses by default?

A

Point-to-multipoint and loopbacks

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16
Q

How can a loopback address be sent with the full subnet mask?

A

Set the loopback as a point-to-point link.

interface Loopback0
ip ospf network point-to-point

17
Q

What is a type 1 LSA?

A

Type 1 router LSA

18
Q

What is a type 2 LSA?

A

A type 2 network LSA is sent by a DR on multiaccess networks advertising the subnet, mask, and all neighbor router-ids in the network.

19
Q

What does a type 3 LSA include?

A

A type 3 summary LSA includes the subnet and mask, with the advertising router set as the ABR’s router-id.

20
Q

How do other routers learn a router is an ABR or ASBR?

A

The flags are present in the type 1 router LSAs

21
Q

What type of LSA do area border routers send?

A

type 3 summary LSA

22
Q

Give the command to view all type 3 LSAs.

A

sh ip ospf database summary

23
Q

How often do routers flood type 1 LSAs if there are no changes?

A

Every thirty minutes they flood and reset the timer.

24
Q

Is a type 3 LSA flooded through an ABR?

A

Technically the ABR will create its own new type 3 LSA.

25
Q

What is a type 5 LSA?

A

A type 5 external LSA is created by an ASBR.

26
Q

What are the LSID and data fields in a type 5 LSA?

A

The LSID in a type 5 external LSA is the subnet, and the data field contains the mask.

27
Q

What is the default cost for a type 5 LSA?

A

1

28
Q

What are the two sub-types for type 5 LSAs? Which is the default?

A

Subtype 1, where receiving routers calculate their own additional costs to get to the ASBR, and subtype 2, where they do not. Subtype 2 is the default.

29
Q

Which routers receive type 5 LSAs?

A

Type 5 LSAs are flooded to all of the routers in the domain, except stub areas.

30
Q

What type of LSA is sent into stub areas as a default route and what is the default metric?

A

A type 3 summary LSA with a metric of one.

31
Q

Which kinds of LSAs do stub routers not receive?

A

They do not receive type 5 external network LSAs and may or may not receive type 3 LSAs, depending on the stub type.

32
Q

Which type of LSAs do not show under a specific area with “sh ip ospf database”?

A

type 5 external LSAs

33
Q

What is a type 7 LSA?

A

A type 7 NSSA external LSA is sent by ASBRs in a not-so-stubby area.

34
Q

Where are type 7 LSAs flooded?

A

Type 7 NSSA external LSAs are flooded to all routers in the domain, except they are changed into a type 5 external LSA at the first ABR they hit.

35
Q

What are the two subtypes for type 7 LSAs? Which is the default?

A

Sub-type 1 increments the router’s cost to get to the ASBR to the LSA’s cost. Sub-type 2 (the default) does not.

36
Q

What is the default metric for a type 7 LSA?

A

20

CCNP Route (9 decks)

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