EIGRP Questions 2
Here you will find answers to EIGRP Questions – Part 2
Note: If you are not sure about EIGRP, please read my EIGRP tutorial
Which two statements are true regarding EIGRP? (Choose two)
A. Passive routes are in the process of being calculated by DUAL
B. EIGRP supports VLSM, route summarization, and routing update authentication.
C. EIGRP exchanges full routing table information with neighboring routers with every update.
D. If the feasible successor has a higher advertised distance than the successor route, it becomes the primary route.
E. A query process is used to discover a replacement for a failed route if a feasible successor is not identified from the current routing information.
Answer: B E
The following are four types of EIGRP route entries. Which of them describes a feasible successor?
A. a backup route, stored in the routing table
B. a primary route, stored in the topology table
C. a primary route, stored in the routing table
D. a backup route, stored in the topology table
EIGRP builds and maintains three tables:
+ Neighbor table: lists directly connected routers running EIGRP with which this router has an adjacency
+ Topology table: lists all routes learned from each EIGRP neighbor -> the feasible successors are stored here!
+ Routing table: lists all best routes from the EIGRP topology table and other routing processes -> only successors are stored here.
Below is the output of a router.
Gateway of last resort is not set
192.168.25.0 /30 is subnetted, 4 subnets
D 192.168.25.20 [90/2681856] via 192.168.15.5, 00:00:10, Serial0/1
D 192.168.25.16 [90/1823638] via 192.168.15.5, 00:00:50, Serial0/1
D 192.168.25.24 [90/3837233] via 192.168.15.5, 00:05:23, Serial0/1
D 192.168.25.28 [90/8127323] via 192.168.15.5, 00:06:45, Serial0/1
C 192.168.15.4/30 is directly connected, Serial0/1
C 192.168.2.0/24 is directly connected, FastEthernet0/0
Which address and mask combination represents a summary of the routes learned by EIGRP?
A. 192.168.25.0 255.255.255.240
B. 192.168.25.28 255.255.255.240
C. 192.168.25.16 255.255.255.252
D. 192.168.25.16 255.255.255.240
E. 192.168.25.28 255.255.255.252
F. 192.168.25.0 255.255.255.252
From the output above, EIGRP learned 4 routes and we need to find out the summary of them:
-> The increment should be: 28 – 16 = 12 but 12 is not an exponentiation of 2 so we must choose 16 (24). Therefore the subnet mask is /28 (=1111 1111.1111 1111.1111 1111.1111 0000) = 255.255.255.240
So the best answer should be 192.168.25.16 255.255.255.240
Enhanced Interior Gateway Routing Protocol – (EIGRP) is a Cisco proprietary routing protocol loosely based on their original IGRP. A router has EIGRP configured as the only routing protocol.
How does EIGRP respond if there is no feasible successor route to a destination network and the successor route fails?
A. It immediately sends its entire routing table to its neighbors.
B. EIGRP sends a Hello packet to the DR to inform it of the route failure.
C. It automatically forwards traffic to a fallback default route until a new successor route is found.
D. It sends queries out to neighbors until a new successor route is found.
E. It places the route in holddown until LSA updates inform it of a new route to the network.
EIGRP sends a query when a route is lost and the feasible route (for that path) does not exist in the topology table
Router# show ip eigrp topology 10.0.0.5 255.255.255.255
IP-EIGRP topology entry for 10.0.0.5/32 State is Passive, Query origin flag is 1, 1 Successor(s), FD is 41152000
Given the output from the show ip eigrp topology command, which router is the feasible successor?
A. Router A.
10.1.0.1 (serial0), from 10.1.0.1 composite
metric is 46152000/41640000
B. Router B.
10.0.0.2 (serial0.1), from 10.0.0.2
composite metric is 53973240/120256
C. Router C.
10.1.0.3 (serial0), from 10.1.0.3
composite metric is 46866176/46354176
D. Router D.
10.1.1.1 (serial0.1), from 10.1.1.1
composite metric is 46670776/46251776
First we must notice that all the 4 answers are parts of the “show ip eigrp topology” output. As you can see, there are 2 parameters in the form of [FD/AD] in each answer. For example answer A has [46152000/41640000], it means that the FD of that route is 46152000 while the AD is 41640000.
To become a feasible successor, a router must meet the feasibility condition:
“To qualify as a feasible successor, a router must have an AD less than the FD of the current successor route“
In four answer above, only answer B has an AD of 120256 and it is smaller than the FD of the current successor route (41152000) so it is the feasible successor -> B is correct.
When running EIGRP what is required for RouterA to exchange routing updates with RouterC?
A. AS numbers must be changed to match on all the routers.
B. Loopback interface must be configured so a DR is elected.
C. The no auto-summary command is needed on Router A and Router C.
D. Router B needs to have two network statements, one for each connected network.
We notice that 3 routers are using different AS numbers so they do not become neighbors and cannot exchange their routing updates. We need to choose only one AS number and use it on all 3 routers to make them exchange routing updates.
In this case we don’t need to use the “no auto-summary” command because network 10.0.0.0 is not separated by another major network.
For the following routing protocols, which one uses bandwidth and delay as metrics by default?
A router is running three routing processes: RIP, OSPF, and EIGRP, each configured with default characteristics. Each process learns a route to the same remote network.
If there are no static routes to the destination and none of the routes were redistributed, which route will be placed in the IP routing table?
A. the route learned through EIGRP
B. the route learned through OSPF
C. the route learned through RIP
D. the route with the lowest metric
E. all three routes with the router load balancing
To support the following IP addressing scheme, which routing protocols will be used? (Choose three)
Network 1 -192.168.10.0/26
Network 2 -192.168.10.64/27
Network 3- 192.168.10.96/27
Network 5-192.168.10.132 /30
D. RIP version 2
E. RIP version 1
Answer: A C D
All 5 networks above are subnetted -> all the classless routing protocols can be used as they do send the subnet mask in their updates so Variable Length Subnet Masks (VLSMs) are supported.
Which routing protocols can be used within the enterprise network shown in the diagram? (Choose three)
A. RIP v1
Answer: B D F