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ICND2 – OSPF Questions 2

October 13th, 2017 in ICND2 200-105 Go to comments

Question 1

Explanation

Router_E learns two subnets subnets 208.149.23.64 and 208.149.23.96 via Router_A through FastEthernet interface. The interface cost is calculated with the formula 108 / Bandwidth. For FastEthernet it is 108 / 100 Mbps = 108 / 100,000,000 = 1. Therefore the cost is 12 (learned from Router_A) + 1 = 13 for both subnets -> B is not correct.

The cost through T1 link is much higher than through T3 link (T1 cost = 108 / 1.544 Mbps = 64; T3 cost = 108 / 45 Mbps = 2) so surely OSPF will choose the path through T3 link -> Router_E will choose the path from Router_A through FastEthernet0/0, not Serial1/0 -> C & D are not correct.

In fact, we can quickly eliminate answers B, C and D because they contain at least one subnet learned from Serial1/0 -> they are surely incorrect.

Question 2

Explanation

The ‘network … area …’ command under OSPF process has the following meaning: It searches all the active interfaces, if the IP address of that interface belong to the ‘network …’ configured under OSPF process then the router will run OSPF on that interface. Therefore when we configure ‘network 0.0.0.0 255.255.255.255 area 0’ command, all interfaces are matched -> OSPF is enabled on all active interfaces on the router.

Question 3

Question 4

Question 5

Explanation

The well-known formula to calculate OSPF cost is

Cost = 108 / Bandwidth

so B is the correct answer.

Question 6

Explanation

The default number of equal-cost paths that can be placed into the routing of a Cisco OSPF router is 4. We can change this default value by using “maximum-paths” command:

Router(config-router)#maximum-paths 2

Note: Cisco routers support up to 16 equal-cost paths

Question 7

Explanation

Link-state protocol uses hello packets to discover neighbors and establish adjacencies. After that, the routers begin sending out LSAs to every neighbor (each received LSA is copied and forwarded to every neighbor except the one that sent the LSA)

Question 8

Question 9

Explanation

The Administrative Distances (AD) of popular routing protocols are listed below:

Administrative Distances_popular_routing_protocols.jpg

Question 10

Comments (5) Comments
  1. Anonymous
    May 3rd, 2017

    Are there any OSPF IPv6 questions on current 200-125 or 200-105 exams?

  2. JJ
    May 4th, 2017

    Why isn’t the answer for question 8 C?

  3. Don’t Spam
    May 14th, 2017

    @JJ.
    If there is no OSPF Router ID configured, the highest IP address on any of the Routers Loopback Interfaces is selected as the OSPF Router ID.

  4. Jesus
    October 8th, 2017

    The correct answer for Q6 is 4? I’m a little confused because Cisco says that by default the path-cost is 16.

    https://www.cisco.com/c/en/us/td/docs/routers/xr12000/software/xr12k_r4-1/routing/configuration/guide/routing_cg41xr12k_chapter4.html

  5. Anonymous
    October 24th, 2017

    @JJ It always uses the highest loopback IP as RID if enabled.