07 - Implementing OSPF Flashcards Preview

CCNP Enterprise ENCOR 350-401 > 07 - Implementing OSPF > Flashcards

Flashcards in 07 - Implementing OSPF Deck (39)
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1
Q

Do routers have to have the same process ID?

A

No

2
Q

What is the router ID election process?

A
  • Manually set RID
  • Highest loopback
  • Highest set active IPv4
3
Q

Hello packets are periodically sent to the multicast address _____.

A

224.0.0.5

4
Q

Neighbour relationship is formed if two routers agree on:

A
  • Area ID
  • Hello and dead intervals
  • Authentication
  • Same subnet
5
Q

What are the OSPF packet types?

A
  • Hello
  • DBD
  • LSR
  • LSU
  • LSAck
6
Q

OSPF packet type - discovers and maintains neighbours

A

Hello

7
Q

OSPF packet type - contain the LSA headers that help build the database

A

DBD

8
Q

OSPF packet type - After DBDs are exchanged, router checks the LSA headers again its own database. If it does not have current information for any LSA, it generates a ___ packet and sends it to its neighbour

A

LSR

9
Q

OSPF packet type - contains a list of LSAs that should be updated. Often used in flooding

A

LSU

10
Q

OSPF packet type - help to ensure a reliable transmission of LSAs. Each LSA is explicitly acknowledged

A

LSAck

11
Q

OSPF has protocol number __.

A

89

12
Q

What are the LSA types?

A
  • 1 Router LSA
  • 2 Network LSA
  • 3 ABR Summary
  • 4 ASBR summary
  • 5 Autonomous system
  • 6-11 other types
13
Q

LSA type: describes the state of the router links to the area and flooded within that particular area

A

1 - router LSA

14
Q

LSA type: describe the set of routers that are attached to a particular multiaccess network

A

2 - Network LSA

15
Q

LSA type: takes the information it learned in one area and summarised it for another area

A

3 - ABR summary

16
Q

LSA type: informs the rest of the OSPF domain how to get to the ASBR.

A

4 - ASBR summary

17
Q

LSA type: generated by ASBRs, describes routes to destinations that are external to the AS. They get flooded everywhere except special areas.

A

5 - Autonomous system

18
Q

In the configuration of the OSPF router if either of the following commands are used, the route becomes an ASBR:

A
  • Resdistribute….

* Default-information originate

19
Q

What are the OSPF neighbour states?

A
  • Down – no neighbour detected
  • Init – hello packet received from neighbour
  • Two way – own router id in received hello
  • Exstart – master and slave roles determined
  • Exchange – DBD packets sent
  • Loading – exchange of LSRs and LSUs
  • Full – fully adjacent
20
Q

How do you observe routes in a routing table?

A

show ip route ospf

21
Q

How do you observe all ospf routes?

A

show ip ospf route

22
Q

How do you observe ospf neighbour adjacency formation?

A
  1. Debug ip ospf adj

2. Clear ip ospf process

23
Q

What are the benefits of having a DR/BDR?

A
  • Reduces routing update traffic – central point of contact for link-state information exchange
  • Manages link-state synchronisation – DR & BDR ensures other routes have same link-state information about common segment
24
Q

What is the multicast IP to communicate with the DR ?

A

224.0.0.6

25
Q

OSPF ___ is used to elect DR/BDR

A

priority - a value between 0-255

26
Q

If there is a tie where routers have same priority value, the __is the tie breaker. Highest __ becomes the DR. 2nd highest BDR

A

router ID

27
Q

Router with a priority of _ cannot be DR/BDR.

A

0

28
Q

What is the default priority?

A

1

29
Q

Router that is not the DR/BDR is called the ____.

A

DROTHER

30
Q

The IP __ determines the maximum size of the packet that can be forwarded without fragmentation

A

MTU

31
Q

Mistmatched MTUs can lead to …

A

Inconsistent OSPF databases

32
Q

OSPF neighbours with mismatches MTUs are stuck in the ___ adjacency state

A

EXSTART

33
Q

How do you change the MTU?

A

ip mtu 1500

34
Q

What is the default value of the OSPF hello interval on broadcast multiaccess and p2p links?

A

10 seconds

35
Q

What is the default value of the OSPF dead interval on broadcast multiaccess and p2p links?

A

40 seconds - 4 times the hello interval

36
Q

What is the value of the OSPF hello/dead interval on all other OSPF network types including NBMA such as frame relay?

A

30/120 seconds

37
Q

How do you change the hello an dead timers?

A
  • Ip ospf hello-interval X

* Ip ospf dead-interval x

38
Q

You can view detailed states such as how long a neighbour has been up with what command?

A

show ip ospf neighbour detail

39
Q

How do you change the the OSPF network type?

A

Using interface command – ip ospf network network type