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Enterprise Networking > Module 2 OSPF > Flashcards

Module 2 OSPF Flashcards

1
Q

What is an OSPF router ID?

A

A 32-bit value represented as an IPv4 address, used to uniquely identify an OSPF router.

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2
Q

What are the two ways an OSPF router ID can be defined?

A
  • Defined by an administrator
  • Automatically assigned by the router
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3
Q

What role does the router ID play in OSPF database synchronization?

A

During the Exchange State, the router with the highest router ID sends their database descriptor (DBD) packets first.

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4
Q

In a multiaccess LAN environment, how is the designated router (DR) elected?

A

The router with the highest router ID is elected as the DR.

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5
Q

What is the function of the backup designated router (BDR)?

A

The BDR serves as a backup in case the DR fails.

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6
Q

What command is used to verify OSPF router roles?

A

show ip ospf interface

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7
Q

What does the output of the ‘show ip ospf interface’ command indicate about R3?

A

R3 is the DR with router ID 3.3.3.3.

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8
Q

What is the default priority for OSPF routers?

A

1

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9
Q

What is the multicast address used by the DR for OSPF?

A

224.0.0.5

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10
Q

What is the address used by DROTHERs to send OSPF packets?

A

224.0.0.6

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11
Q

What state indicates a router is fully adjacent with a DR?

A

FULL/DR

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12
Q

What does the term FULL/DROTHER indicate?

A

A DR or BDR router that is fully adjacent with a non-DR or BDR router.

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13
Q

What happens to the DR if it fails?

A

The BDR is automatically promoted to DR.

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14
Q

What is the default reference bandwidth for OSPF cost calculation?

A

100,000,000 bps

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15
Q

What is the formula to calculate OSPF cost?

A

Cost = reference bandwidth / interface bandwidth

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16
Q

What command adjusts the reference bandwidth on OSPF routers?

A

auto-cost reference-bandwidth

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17
Q

True or False: A router with a priority of 0 can be elected as DR or BDR.

A

False

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18
Q

What command is used to change the OSPF priority of an interface?

A

ip ospf priority [value]

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19
Q

What happens if all routers have the same interface priority?

A

The router with the highest router ID is elected as DR.

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20
Q

What is a DROTHER?

A

A router that is neither the DR nor the BDR.

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21
Q

What does the command ‘show ip ospf neighbor’ verify?

A

It verifies the OSPFv2 adjacencies.

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22
Q

What is the state of a non-DR router that has a neighbor relationship with another non-DR router?

A

2-WAY/DROTHER

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23
Q

What must happen for a new BDR election to occur?

A

The current BDR must be promoted to DR.

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24
Q

If the DR fails, what will happen to the BDR?

A

The BDR is automatically promoted to DR.

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25
What is the significance of the 'show ip ospf neighbor' command output for R2?
It confirms R2's adjacencies with R1 and R3, showing their states.
26
What happens if the DR fails?
The BDR is automatically promoted to DR.
27
What is the result after a BDR is promoted to DR?
A new BDR election occurs.
28
What is the basic syntax for the OSPF network command?
Router(config-router)# network network-address wildcard-mask area area-id
29
What does the wildcard mask represent?
The inverse of the subnet mask configured on that interface.
30
How can a router ID be explicitly configured?
Using the command 'router-id rid' in router configuration mode.
31
What is the preferred method to reset the router ID?
Clearing the OSPF process.
32
What is the order of precedence for deriving the OSPF router ID?
* Explicitly configured router ID * Highest IPv4 address of any configured loopback interfaces * Highest active IPv4 address of any physical interfaces
33
What command is used to configure OSPF directly on an interface?
ip ospf process-id area area-id
34
What is the default behavior of OSPF messages on interfaces?
OSPF messages are forwarded out all OSPF-enabled interfaces.
35
What command can you use to prevent routing messages from being sent out an interface?
passive-interface
36
True or False: Loopback interfaces are advertised as /32 host routes by default.
True
37
What command can be used to verify OSPF operation?
show ip protocols and show ip route
38
Fill in the blank: The _______ command can be used to configure passive interfaces.
passive-interface
39
What command is used to enable a point-to-point network?
ip ospf network point-to-point
40
What is the effect of sending unnecessary OSPF messages on a LAN?
* Inefficient use of bandwidth * Inefficient use of resources * Increased security risk
41
What is the recommended area ID to use with single-area OSPFv2?
Area ID 0
42
What command syntax is used to configure the network command on R1?
network 10.10.1.0 0.0.0.255 area 0
43
What does the command 'clear ip ospf process' do?
Resets all OSPF processes.
44
What command shows the current router ID?
show ip protocols | include Router ID
45
What should the IPv4 address for a loopback interface be configured with to serve as a router ID?
A 32-bit subnet mask (255.255.255.255)
46
What is the advantage of specifying the exact interface IPv4 address using a quad zero wildcard mask?
No wildcard mask calculation is necessary.
47
What command is used to verify the OSPF interface configuration?
show ip ospf interface
48
What command is used to enable OSPFv2?
router ospf process-id ## Footnote The process-id value is a number between 1 and 65,535 and is locally significant.
49
What is considered best practice regarding OSPF process ID?
Use the same process-id on all OSPF routers ## Footnote This helps maintain consistency across the OSPF network.
50
What does the command 'show ip protocols' display?
Vital OSPF configuration information including: * OSPFv2 process ID * Router ID * Interfaces configured to advertise OSPF routes * Neighbors receiving updates * Default administrative distance
51
What is the default administrative distance for OSPF?
110
52
What can cause two routers to not form an OSPFv2 adjacency?
The following issues can prevent adjacency: * Subnet masks do not match * OSPFv2 Hello or Dead Timers do not match * OSPFv2 Network Types do not match * Missing or incorrect OSPFv2 network command
53
Fill in the blank: To adjust the reference bandwidth, use the command _______.
auto-cost reference-bandwidth Mbps
54
What command can be used to verify OSPF neighbors?
show ip ospf neighbor
55
What does the command 'show ip ospf interface brief' provide?
A quick summary of OSPFv2-enabled interfaces including: * Interfaces participating in OSPF * Advertised networks (IP Address/Mask) * Cost of each link * Network state * Number of neighbors on each link
56
How do you configure OSPF to propagate a default route?
Configure: * A default static route using 'ip route 0.0.0.0 0.0.0.0 [next-hop-address | exit-intf]' * 'default-information originate' command
57
True or False: The reference bandwidth must be configured on every router in the OSPF domain.
True
58
What happens if the calculated cost value for OSPF is less than an integer?
OSPF rounds up to the nearest integer.
59
What command is used to manually set the OSPF cost value on an interface?
ip ospf cost value
60
What is the maximum number of paths OSPF can use?
4
61
What command can be used to verify the OSPF process information?
show ip ospf
62
What information does 'show ip ospf interface' provide?
Detailed list for every OSPFv2-enabled interface including: * Process ID * Local router ID * Type of network * OSPF cost * DR and BDR information * Adjacent neighbors
63
What is the purpose of the 'passive-interface' command in OSPF?
Suppress routing updates on an interface
64
What does the 'redistribute' command do in OSPF?
Redistribute information from another routing protocol
65
What is the command to check the routing table for a specific network?
show ip route | include [network]
66
What is the command to configure a router ID for OSPF?
router ospf [process-id] ## Footnote The router ID is specified during OSPF configuration.
67
Fill in the blank: The default reference bandwidth is _______.
100 Mbps
68
What command is used to show the routing entry for a specific IP address?
show ip route [IP address] ## Footnote For example, 'show ip route 10.10.2.0'.
69
What is the distance and metric for the OSPF route to 10.10.2.0/24?
Distance: 110, Metric: 11 ## Footnote The route is known via 'ospf 10'.
70
What is the total cost for R1 to reach the 10.10.2.0/24 network?
11 ## Footnote This is calculated as the link to R2 cost (10) plus the loopback default cost (1).
71
What command can be used to verify the current OSPFv2 cost assigned to an interface?
show ip ospf interface ## Footnote This command provides details on the OSPF configuration for that interface.
72
How does OSPF accumulate cost?
The cost is the accumulated value from one router to the destination network. ## Footnote The cost reflects the link costs and default costs of loopback interfaces.
73
What happens if the link between R1 and R2 goes down?
The routing table updates to use R3 as the next-hop router. ## Footnote R1 can reach the 10.1.1.4/30 network through R3 with a cost value of 50.
74
What are the default Hello and Dead intervals for OSPF?
Hello interval: 10 seconds, Dead interval: 40 seconds ## Footnote These values are configurable on a per-interface basis.
75
What command is used to change the OSPF Hello interval?
ip ospf hello-interval [seconds] ## Footnote This command is entered in interface configuration mode.
76
What is the purpose of Hello packets in OSPF?
Hello packets establish and maintain neighbor relationships between routers. ## Footnote They are transmitted every 10 seconds to multicast address 224.0.0.5.
77
True or False: OSPF Hello packets are sent on passive interfaces.
False ## Footnote Hello packets are not sent on interfaces set to passive by the passive-interface command.
78
Fill in the blank: The _______ interval is the period that the router waits to receive a Hello packet before declaring the neighbor down.
Dead ## Footnote If the Dead interval expires without receiving a Hello packet, OSPF will remove that neighbor from its LSDB.
79
What command is used to verify the neighbor adjacencies in OSPF?
show ip ospf neighbor ## Footnote This command displays the state and Dead Time of OSPF neighbors.
80
What is the result of modifying the Hello interval to 5 seconds?
The Dead interval is automatically adjusted to 20 seconds. ## Footnote This is four times the Hello interval.
81
What is the significance of the 'O*E2' designation in the routing table?
'O*E2' indicates the route was learned using OSPFv2 and is an external route. ## Footnote The asterisk identifies it as a valid candidate for the default route.
82
How can you verify the default route settings on a router?
Use the command show ip route ## Footnote This will display the routing table, including any default routes.
83
What does the command 'auto-cost reference-bandwidth 10000' do in OSPF?
It sets the reference bandwidth for OSPF cost calculations. ## Footnote This is important for adjusting OSPF costs based on the speed of links.

Enterprise Networking (1 decks)

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