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OSPF Questions 2

November 4th, 2017 Go to comments

Question 1

Explanation

In IPv6, you can configure many address prefixes on an interface. In OSPFv3, all address prefixes on an interface are included by default. You cannot select some address prefixes to be imported into OSPFv3; either all address prefixes on an interface are imported, or no address prefixes on an interface are imported.

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/15-sy/iro-15-sy-book/ip6-route-ospfv3.html

Question 3

Question 4

Explanation

Because the destination of 172.16.1.1 is not present in the routing table so this router would use the default route (O*E2) to forward this packet. Usually the O*E2 is the result of the “default-information originate” command on the upstream router.

Question 5

Question 6

Explanation

Before we can implement OSPFv3 we need to configure an IPv4 router ID (although OSPFv3 deals with IPv6 addresses, it still uses 32-bit router ID) on that device and enable IPv6 unicast routing (via the “ipv6 unicast-routing” in global configuration mode).

Note: If we have already had an active interface, we don’t need to configure the router ID for OSPFv3 anymore because the device will automatically choose that IPv4 address for its router ID).

Question 7

Question 8

Explanation

Hierarchical design of OSPF (basically means that you can separate the larger internetwork into smaller internetworks called areas) helps us create a network with all features listed above (decrease routing overhead, speed up convergence, confine network instability to single areas of the network).

Question 9

Question 10

Explanation

To form an adjacency (become neighbor), router A & B must have the same Hello interval, Dead interval and AREA number.

Comments (6) Comments
  1. nickaro
    September 12th, 2017

    In Q4 192.168.1.1 is included in route 192.168.0.0/16. So packets are sent to 192.168.15.5 out interface Fa1/1. Am I right?

  2. nickaro
    September 20th, 2017

    I’ve just realized of my mistake. Destiny IP is 172.16.1.1, not 192.168.1.1 :-(

  3. Tech Explorer
    December 27th, 2017

    Answer to question 6 is wrong. Right answer is:

    if ipv4 address does NOT exist: configure router id
    if ipv4 address does exist: no need to configure router id

    Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6/configuration/xe-3s/ipv6-xe-36s-book/ip6-ospf.html#GUID-C38CCDD0-560F-4CD2-A199-13930C6B0FE9

  4. mm
    January 10th, 2018

    Answer to Q6 should be D and E because we dont need to configure router id as the router already configured for ipv4.

  5. sachu
    January 11th, 2018

    @9tut
    Question 6 – How do we create IPv4 router id ? you have to configure it inside the ipv6 router ospf 1 !that means while your creating the ospv3 process. The question is” Before ” you implement ospfv3. so the correct answer would be E- enable ipv6 unicast routing and D- Enable IPv6 on an interface

  6. sadhu
    January 15th, 2018

    Question 6 – discard the previous post

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