Home > ICND2 – EIGRP Questions 4

ICND2 – EIGRP Questions 4

October 12th, 2017 in ICND2 200-105 Go to comments

Question 1

Explanation

From the output we see a line “Gateway of last resort is 192.168.4.1 to network 0.0.0.0”. Gateway of last resort refers to the next-hop router of a router’s current default route. Therefore all the traffic through this router to destination networks not matching any other networks or subnets in the routing table will be sent to 192.168.4.1 (which is on Serial2) -> packet destined for 192.0.2.156 (or an unknown destination) will be forwarded via Serial2.

An weird thing in the output above is the missing of the asterisk mask (*) which represents for the candidate default route. To set the “Gateway of last resort is 192.168.4.1 to network 0.0.0.0” as the output above we can use these commands:

ip route 0.0.0.0 0.0.0.0 192.168.4.1
ip default-network 192.168.4.0

But these commands will create an static routing in the routing table with an asterisk mask. Maybe the output shown above is missing that route.

For more information about the command ip default-network please visit: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094374.shtml.

Question 2

Explanation

From the output of “show ip route” command on RouterB, we learn that RouterB does not learn any networks in RouterA. Also the “172.16.0.0/26 is a summary, 00:00:03, Null0” line tells us this netwok is summarized.

Note: EIGRP performs auto-summarization each time it crosses a border between two major networks. For example, RouterA has networks of 172.16.x.x. It will perform auto-summarization when sending over network 10.1.1.0/30, which is in different major network (172.16.0.0/16 and 10.0.0.0/8 are called major networks in this case).

Question 3

Explanation

All the above networks can be summarized to 10.0.0.0 network but the question requires to “represent the LANs in Phoenix but no additional subnets” so we must summarized to 10.4.0.0 network. The Phoenix router has 4 subnets so we need to “move left” 2 bits of “/24”-> /22 is the best choice -> D is correct.

Question 4

Explanation

From the line “D 192.168.20.64/26 [90/2195456] via 192.168.20.9, 00:03:31, Serial0/0″ we can see the IP address 192.168.20.9 belongs to network 192.168.20.8/30 and this network is between R1 and R3 -> Packet from 192.168.20.192/26 network destined to a host on the LAN attached to router R1 will go directly from R3 to R1.

Question 5

Explanation

From the routing table we learn that network 192.168.10.0/30 is learned via 2 equal-cost paths (192.168.10.9 &192.168.10.5) -> traffic to this network will be load-balancing.

Question 6

Explanation

C is not correct because successor routes are not flagged as “active”, they are always the best route to reach remote networks and are always used to send packets.

A and D are correct because successor route is the best and primary route to a remote network. It is stored in the routing table and topology table. If this route fails, a backup route (called feasible successor route) in the topology table will be used to route traffic to a destination.

E is not correct because neighbor table only contains a list of directly connected EIGRP routers that have an adjacency with this router, it doesn’t contain successor routes.

Question 7

Question 8

Explanation

Below is an example of the “show ip eigrp neighbors” command (from 9tut.com)

EIGRP_show_ip_eigrp_neighbors.jpg

Question 9

Question 10

Question 11

Comments (1) Comments
  1. Question 1s link is outdated, try this
    November 29th, 2017

    #7s answer is based on the adjacent route having the highest available bandwidth?