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OSPF Questions 2

July 28th, 2017 in ROUTE 300-101 Go to comments

Question 1

Explanation

Exstart: Once the DR and BDR are elected, the actual process of exchanging link state information can start between the routers and their DR and BDR. In this state, the routers and their DR and BDR establish a master-slave relationship and choose the initial sequence number for adjacency formation. The router with the higher router ID becomes the master and starts the exchange, and as such, is the only router that can increment the sequence number. Note that one would logically conclude that the DR/BDR with the highest router ID will become the master during this process of master-slave relation.

Reference: http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13685-13.html

Question 2

Question 3

Question 4


Question 5

Explanation

+ Standard areas can contain LSAs of type 1, 2, 3, 4, and 5, and may contain an ASBR. The backbone is considered a standard area.
+ Stub areas can contain type 1, 2, and 3 LSAs. A default route is substituted for external routes.
+ Totally stubby areas can only contain type 1 and 2 LSAs, and a single type 3 LSA. The type 3 LSA describes a default route, substituted for all external and inter-area routes.
+ Not-so-stubby areas implement stub or totally stubby functionality yet contain an ASBR. Type 7 LSAs generated by the ASBR are converted to type 5 by ABRs to be flooded to the rest of the OSPF domain.

Reference: http://packetlife.net/blog/2008/jun/24/ospf-area-types/

Question 6

Explanation

NSSA External LSA (Type 7) – Generated by an ASBR inside a Not So Stubby Area (NSSA) to describe routes redistributed into the NSSA. LSA 7 is translated into LSA 5 as it leaves the NSSA. These routes appear as N1 or N2 in the routing table inside the NSSA. Much like LSA 5, N2 is a static cost while N1 is a cumulative cost that includes the cost upto the ASBR.

OSPF_LSAs_Types_7.jpg

Question 7

Explanation

OSPFv3 uses the well-known IPv6 multicast addresses, FF02::5 to communicate with neighbors.

Note: All other routers (non DR and non BDR) establish adjacency with the DR and the BDR and use the IPv6 multicast address FF02::6 to send LSA updates to the DR and BDR.

Question 8

Explanation

NSSA External LSA (Type 7) – Generated by an ASBR inside a Not So Stubby Area (NSSA) to describe routes redistributed into the NSSA. LSA 7 is translated into LSA 5 as it leaves the NSSA. These routes appear as N1 or N2 in the routing table inside the NSSA. Much like LSA 5, N2 is a static cost while N1 is a cumulative cost that includes the cost upto the ASBR.

OSPF_LSAs_Types_7.jpg

Question 9

Question 10

Comments
  1. Anonymous
    August 5th, 2017

    Hi!

    Can you please confirm the answer to question 1, i think its B (Loading)

    https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13685-13.html

    Loading

    In this state, the actual exchange of link state information occurs. Based on the information provided by the DBDs, routers send link-state request packets. The neighbor then provides the requested link-state information in link-state update packets.

  2. Sq
    August 6th, 2017

    Question 3

    Refer to the exhibit. A network engineer executes the show ipv6 ospf database command and is presented with the output that is shown. Which flooding scope is referenced in the link-state type?
    (Exhibit missing)

    A. link-local
    B. area
    C. AS (OSPF domain)
    D. reserved

    The exibit is showing:

    Link (Type-8) Link states (Area 0)

    As its type 8 shouldn’t it be the link-local flooding scope ?

  3. anu
    August 18th, 2017

    Refer to the exhibit. A network engineer executes the show ipv6 ospf database command and is presented with the output that is shown. Which flooding scope is referenced in the link-state type?
    (Exhibit missing)

    A. link-local
    B. area
    C. AS (OSPF domain)
    D. reserved

    Whats the correct answer?

  4. anu
    August 18th, 2017

    When OSPF is forming an adjacency, in which state, the actual exchange of information in the link?
    A. INIT
    B. loading
    C. exstart
    D. exchange

    Whats the answer?

    Exstart

    Once the DR and BDR are elected, the actual process of exchanging link state information can start between the routers and their DR and BDR.
    In this state, the routers and their DR and BDR establish a master-slave relationship and choose the initial sequence number for adjacency formation. The router with the higher router ID becomes the master and starts the exchange, and as such, is the only router that can increment the sequence number. Note that one would logically conclude that the DR/BDR with the highest router ID will become the master during this process of master-slave relation. Remember that the DR/BDR election might be purely by virtue of a higher priority configured on the router instead of highest router ID. Thus, it is possible that a DR plays the role of slave. And also note that master/slave election is on a per-neighbor basis.

    Loading

    In this state, the actual exchange of link state information occurs. Based on the information provided by the DBDs, routers send link-state request packets. The neighbor then provides the requested link-state information in link-state update packets. During the adjacency, if a router receives an outdated or missing LSA, it requests that LSA by sending a link-state request packet. All link-state update packets are acknowledged.

  5. Pif
    August 19th, 2017

    Hello anu,

    Please , it will be helpful to share the dumps. I don’t find the questions.

    my e mail is loofy666 @ gmail . com

    I download from this site Route_April_2016 but the questions don’t correspond .

    Please help me

  6. Anonymous
    August 21st, 2017

    Passed today 9xx,
    Study the labs from here and check out for the latest dumps on IT-Libraries website there are a lot of users that use it and you can see if the dumps are still valid or not.

    good luck

  7. Who am I to judge
    August 22nd, 2017

    @Anu @Sq

    Question3:

    It must be link local

  8. Anonymous
    August 25th, 2017

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    IT Libraries hasn’t got all questions ..

    ACL very important ( IPV6 and IPV4 both)

    I was using my old 642-902 books :(, please get the new cert guide for CCNP route 300-101)

  9. Steffy
    August 28th, 2017

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  10. Anonymous
    September 3rd, 2017

    When OSPF is forming an adjacency, in which state, the actual exchange of information in the link?
    A. INIT
    B. loading
    C. exstart
    D. exchange
    Whats the answer?
    Exstart
    Once the DR and BDR are elected, the actual process of exchanging link state information can start between the routers and their DR and BDR.
    In this state, the routers and their DR and BDR establish a master-slave relationship and choose the initial sequence number for adjacency formation. The router with the higher router ID becomes the master and starts the exchange, and as such, is the only router that can increment the sequence number. Note that one would logically conclude that the DR/BDR with the highest router ID will become the master during this process of master-slave relation. Remember that the DR/BDR election might be purely by virtue of a higher priority configured on the router instead of highest router ID. Thus, it is possible that a DR plays the role of slave. And also note that master/slave election is on a per-neighbor basis.
    Loading
    In this state, the actual exchange of link state information occurs. Based on the information provided by the DBDs, routers send link-state request packets. The neighbor then provides the requested link-state information in link-state update packets. During the adjacency, if a router receives an outdated or missing LSA, it requests that LSA by sending a link-state request packet. All link-state update packets are acknowledged.
    Pif August 19th, 2017
    Hello anu,

  11. Correction
    September 23rd, 2017

    Question 1

    When OSPF is forming an adjacency, in which state, the actual exchange of information in the link?
    A. INIT
    B. loading
    C. exstart
    D. exchange

    B. Loading is the correct answer.

  12. learner
    October 15th, 2017

    Question 1

    I believe based on information from link below it should be C: EXSTART

    When OSPF is forming an adjacency, in which state, the actual exchange of information in the link?
    A. INIT
    B. loading
    C. exstart
    D. exchange

    https://www.computernetworkingnotes.com/ccna-study-guide/ospf-neighbor-states-explained-with-example.html

  13. jonzo
    October 17th, 2017

    Hi folks,

    Can I get clarification on Q1?

    I am uncertain about how it is worded. Is at asking about routing information or link state information?

    Database sequence numbers and master/ slave logic negotiated = exstart state
    Routing information exchanged = loading state

    The answer would depend on the interpretation of the question?

  14. Corner
    November 22nd, 2017

    Q1. Answer is loading.

    exstart = forming master/slave relationship
    exchange = exchange Database Descriptors (LSA headers only)
    loading = exchange of full LSA (the ones the router doesnt have already)

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