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ag-Cisco CCNA 2 > 8 - Implementing OSPF IPV4 > Flashcards

8 - Implementing OSPF IPV4 Flashcards

1
Q

What does the ‘ospf network ‘ do?

A
  • finds the routers interfaces that match the network/wildcard mask
  • enables OSPF on those interfaces
  • DISCOVERS neighbors
  • CREATES RELATIONSHIPS with neighbors
  • ASSIGNS INTERFACES to AREAS
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2
Q

What does wildcard 0.0.0.0 do?

A

all 4 octets must exactly match

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3
Q

What does wildcard 255.255.255.255 do?

A

all addresses will match

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4
Q

What are the 3 steps an OSPF router does to add routes to its routing table?

A
  • create neighbor relationships
  • build and flood LSAs so that each router in that area has identical LSDB
  • computes its IP routes INDEPENDENTLY using SPF and adds them to routing table
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5
Q

What show command verifies neighbors?

A

show ip ospf neighbors

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6
Q

What show command verifies the LSDB?

A

show ip ospf database

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7
Q

What show command verifies the routes?

A

show ip route

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8
Q

What is the difference between a Local route and a Connected route?

A

Local is the local interface with /32 mask, Connected is the subnet the interface connects to.

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9
Q

What are two ways to stop and start the OSPF process?

A
  1. ) Reboot the router

2. ) Use the command ‘clear ip ospf process’

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10
Q

What show command confirms a router’s OSPF ID?

A

show ip ospf

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11
Q

If an interface is configured to be passive what happens?

A
  • Quits sending OSPF Hellos on the interface.
  • Ignores received Hellos on the interface.
  • Does not form neighbor relationships over the interface.
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12
Q

Does a subnet whose interface is passive still get advertised?

A

Yes

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13
Q

What are two ways to configure interfaces as passive?

A

1) in router-config mode use ‘passive-interface fa0/1’ or 2) in router-config mode use ‘passive-interface default’ and then for each interface you don’t want to be passive use ‘no passive-interface fa0/0’

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14
Q

What show command will reveal a passive-interface?

A

show ip ospf interface fa0/0

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15
Q

What kind of routers have interfaces in more than one area?

A

ABRs, Area Boundary Routers

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16
Q

What show commands reveal what area an interface is in?

A
  • show ip ospf interfaces fa0/0

* show ip ospf interfaces brief

17
Q

Which show commands identifies a router as a DR or BDR

A
  • show ip ospf interface brief
  • show ip ospf interface
  • show ip ospf neighbor
18
Q

How are the DR and BDR elected?

A

The highest Router ID wins and is DR, the second highest Router ID is BDR

19
Q

How do Intra-area Routes appear in the ‘show ip route’ cmd output?

A

They show up as an O route (OSPF) and WITHOUT the IA code

20
Q

What is the formula OSPF uses to calculate the cost of an interface?

A

Convert to kilobits/sec and use Reference Bandwidth / interface_bandwidth

21
Q

How does an engineer change the cost of a particular interface?

A

Method 1: go on the interface and configure the cost using ‘ip ospf cost ‘.
Method 2: Change the bandwidth of the interface using ‘bandwidth or
Method 3: Go into OSPF router-config and change the reference bandwidth using the command ‘auto-cost reference-bandwith 10000’ changes reference bandwidth to 10Gbps.

22
Q

What is the command to enable OSPF directly on the interface?

A

interface fa0/0

ip ospf 1 area 23

23
Q

If OSPF is enabled using a network command in router-config what does the output of the ‘show ip ospf interface fa0/0’ show?

A

Attached via Network Statement

24
Q

If OSPF is enabled using a ‘ip ospf 1 area 23 command in Interface config mode what does the output of the ‘show ip ospf interface fa0/0’ show?

A

Attached via Interface Enable

25
Q

What 4 items make up the OSPF Configuration Checklist

A
  • router ospf
  • router-id
  • network 10.2.2.0 0.0.0.255 area 0
  • passive-interface gig0/1
26
Q

What 3 ‘show’ cmds verify 1) neighbor relationships 2) builds and floods LSAs 3) add routes

A
  • show ip ospf neighbor
  • show ip ospf database
  • show ip route
27
Q

What are some default interface costs?

A
  • 1.54 Mbps = 64
  • 10 Mbps = 10
  • 100 Mbps = 1
28
Q

What is the command to manually configure the interface cost?

A

Interface subcommand: ip ospf cost

29
Q

How do you change the Reference Bandwidth?

A

In router subcommand mode:
auto-cost reference-bandwidth
example: auto-cost reference-bandwidth 10000 will accomodate links up to 10Gbps.

30
Q

How does the reference-bandwidth formula work?

A

reference_bandwidth / actual bandwidth = cost

ag-Cisco CCNA 2 (40 decks)

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