Chapter 9 - Understanding EIGRP Concepts

Question 1

EIGRP uses a robust metric based on what 2 things?

Answer 1

Link bandwidth and link delay.

Question 2

When it comes to routing protocols, what is distance?

Answer 2

The metric for a possible route.

Question 3

When it comes to routing protocols, what is vector?

Answer 3

The direction, based on the next-hop router for a possible route.

Question 4

What does OSPF and EIGRP use to monitor the state of neighboring routers?

Answer 4

Hello messages

Question 5

Distance vector protocols (DV) help prevent routing loops by ensuring that every router learns that the route has failed. What is this called?

Answer 5

Route poisoning

Question 6

What special metric value is advertised with a failed route?

Answer 6

Infinity

Question 7

What’s the default hello and hold interval settings for EIGRP?

Answer 7

5 seconds for Hello messages and 15 seconds for hold interval

Question 8

True or False. The hello and hold intervals have to match between two EIGRP routers.

Answer 8

False. They do not have to match.

Question 9

What is split horizon?

Answer 9

Split horizon is a DV feature that tells the routing protocol to not advertise some routes in an update sent out an interface: routes that list that interface as the outgoing interface.

Question 10

Messages for RIP-2 are sent to what IP address?

Answer 10

224.0.0.9

Question 11

Messages for EIGRP are sent to what IP address?

Answer 11

224.0.0.10

Question 12

Messages for OSPFv2 are sent to what IP addresses?

Answer 12

224.0.0.5 and 224.0.0.6

Question 13

What 3 settings does EIGRP check to determine whether a router should be allowed to be a neighbor?

Answer 13

1. Must pass the authentication process if used.
2. Must use the same configured autonomous system number.
3. The source IP address used by the neighbor’s Hello message must be in the same subnet as the local router’s interface IP address/mask.

Question 14

What’s the difference between a full update and a partial update?

Answer 14

Full update means that a router sends information about all known routes. A partial update includes only information about recently changed routes.

Question 15

When does EIGRP send full updates? When does it send partial updates?

Answer 15

It sends full updates when two routers become neighbors and partial updates when there are changes in the routing table.

Question 16

What is feasible distance in EIGRP?

Answer 16

The local router’s metric of the best route to reach a subnet, as calculated on the local router.

Question 17

What is reported distance in EIGRP?

Answer 17

The next-hop router’s best metric for that same subnet.

Question 18

What is a successor?

Answer 18

For a particular subnet, the route with the best metric.

Question 19

What is a feasible successor?

Answer 19

The route used is the currently best route fails.

Question 20

How is a feasible successor determined?

Answer 20

If a nonsuccessor route’s RD is less than the FD, the route is a feasible successor route.

Question 21

In EIGRP, when a route fails and the route has no feasible successors what happens?

Answer 21

EIGRP uses a distributed algorithm called Diffusing Update Algorithm (DUAL) to choose a replacement route. DUAL sends queries looking for a loop-free route to the subnet in question.