Home > ICND1 – IP Routing 4

ICND1 – IP Routing 4

June 14th, 2017 in ICND1 100-105 Go to comments

Note: The ICND1 exam requires candidates to understand basic knowledge of dynamic routing protocols (RIP, EIGRP, OSPF).

Question 1

Question 2

Question 3

Explanation

A and E are correct according to the theory of RIP.

RIP version 1 updates are broadcasts, and RIP version 2 updates are multicast to 224.0.0.9 -> B is not correct.

RIP v1 is a classful routing protocol but RIP v2 is a classless routing protocol -> C is correct.

RIPv1 and RIPv2 have the same default administrative distance of 120 -> D is not correct.

RIPv2 is a classless routing protocol so it does send the subnet mask in updates -> F is not correct.

Question 4

Explanation

Host1 can ping the Serial interface of R2 because R1 has the network of 192.168.1.4/30 as directly connected route. But R1 does not know how to route to the network of Host2 (192.168.1.128/26) so R1 will drop that ping without trying to send it out S0/0 interface. To make the ping work, we have to configure a route pointing to that network (for example: ip route 192.168.1.128 255.255.255.192 s0/0 on R1).

Question 5

Explanation

The route 192.168.5.0/24 currently has the metric of 15 so this router will add 1 hop count before sending out to its neighboring router. With RIP, a metric of 16 means that network is down -> it will not be installed in the routing table of the neighboring router.

Question 6

Question 7

Explanation

The passive interface only prevents routing updates from being sent and received on that interface. It does not affect the default route. But if we configure a default route like this:

Router(config)#ip route 0.0.0.0 0.0.0.0 192.168.1.2

Then if the next-hop address is down (unreachable) then this default route would be removed from the routing table.

Question 8

Question 9

Comments (6) Comments
  1. Anonymous
    August 18th, 2017

    There is a question in http://www.9tut.net/final_flash/ICND1v3/All_Questions_3/quiz.html
    (Question 11)
    Which information is used to install the best route to a destination in IP routing table?
    a: the Predix Length
    b: the interface number
    c: the autonomous system
    d: the tunnel ID.
    ————————————-
    the correct answer from the quiz is a: the prefix length.

    however, my understanding is: prefix length decided the network mask, like /24 is the 255.255.255.0.

    why not the answer b? my understanding is:
    after configured, each interface has its IP address. the router will know which interface to send out the packet.

    Thanks

  2. Sunil
    November 25th, 2017

    Hi ,
    Ques 5 I am unable to understand this ques .

    question 5: After the show ip route command has been entered, the following routes are displayed. Which route will not be entered into the routing table of a neighboring router??

  3. sharkguy
    November 29th, 2017

    @sunil if you look there are 2 routes for the same network on s0/0. both are using RIP with a AD of 120 but the metric for the one route is 15 which means there is a higher cost to that route. There is some long math algorithm that computes this but f you look under the CCENT study guide you will see a good explanation of this.

    @Anon if you reference the CCENT study guide under dynamic routing protocols you will see that routes first use AD to determine the best route and if they have the same AD they will then use the prefix length to send to the smallest network. check out https://en.wikipedia.org/wiki/Longest_prefix_match

  4. cfish
    December 18th, 2017

    The question 5 states, that “… the following routes are displayed..”. But I cannot find the routes in below. @sharkguy / @Sunil, are you able see them?

  5. Saturn1
    December 23rd, 2017

    The “routes displayed ” are referring to the list of answers, you have to choose from one of them.

  6. David
    January 16th, 2018

    Q8: Which information is used to install the best route to a destination in IP routing table?
    a: the Prefix Length
    b: the interface number
    c: the autonomous system
    d: the tunnel ID.
    ————————————-
    the correct answer from the quiz is a: the prefix length.

    but what is prefix length?