IP routing essentials

Question 1

What is the purpose of a router

Answer 1

To forward traffic between different network segments.

Question 2

How does a router learn about route paths

Answer 2

from static and dynamic routing protocols

Question 3

What is a dynamic routing protocol

Answer 3

A protocol that distributes network topology information between routers and provide ongoing updates to the topology without physical intervention. A dynamic routing protocol will attempt to select the best loop free path to the destination in the current network.

Question 4

What is an Autonomous System (AS)

Answer 4

Is a network of systems running the same dynamic routing protocol and managed under the same network administration.

Question 5

What is an Interior gateway protocol

Answer 5

a routing protocol optimised for routing within an AS

Question 6

What is an exterior gateway protocol

Answer 6

a routing protocol optimised for routing between AS’s

Question 7

What are the different types of dynamic routing algorithms

Answer 7

Distance Vector
Enhanced Distance Vector
Link State
Path Vector

Question 8

What is a distance vector algorithm

Answer 8

determines the best route for data packets based on distance.

Question 9

What routing protocol uses a distance vector algorithm

Answer 9

RIPv2

Question 10

What is the metric used in RIP

Answer 10

Hops to destination

Question 11

Does RIP have a complete map of the network topology

Answer 11

NO

Question 12

What is the advantage of RIP

Answer 12

very low CPU resource consumed.

Question 13

What is the main disadvantage of RIP

Answer 13

It relies purely on hop count, no consideration is taken into the bandwidth of the link.

Question 14

What is an enhanced distance vector algorithm

Answer 14

It is an enhanced version of distance vector that relies on more than just distance(hops) to calculate the metric.

Question 15

What routing protocol uses an enhanced distance vector algorithm

Answer 15

EIGRP

Question 16

What is the metric used in EIGRP

Answer 16

by default (total path delay + minimum bandwidth)

Question 17

Does EIGRP have a complete map of the network topology

Answer 17

No

Question 18

What is the advantage of EIGRP

Answer 18

Rapid convergence time
updates are only sent when there is an update.
Uses multiple attributes to calculate metric not just hop count.
Supports un-equal cost multi pathing

Question 19

What is a link state algorithm, and how does it identify the best path

Answer 19

Each router advertises every connect & directly connected routes and the state of that link to each other router. When the entire topology is learnt. Then Dijkstra’s algorithm is ran to identify the shortest path

Question 20

What are the advertisement packets called in:

OSPF
IS-IS

Answer 20

OSPF: LSA
IS-IS: LSP

Question 21

What is the advantages to link state routing protocols

Answer 21

due to running the Dijkstra algorithm less chance of routing loops

Better path decisions

OSPF and IS-IS have features that allow them to support technology such as MPLS traffic engineering.

Question 22

What is the main disadvantage of link state routing protocols

Answer 22

Due to all routers having to have an identical map of the network to perform the algorithm a high amount of CPU usage is required.

Question 23

What is a path vector algorithm

Answer 23

It uses multiple attributes to calculate metric.

Question 24

What routing protocol uses path vector algorithm

Answer 24

BGP

Question 25

How does BGP prevent routing loops

Answer 25

By recording the AS number of every AS the packets pass through and will automatically drop the packet if it matches

Question 26

When multiple paths have the same destination network address what is the process for selecting the route to be installed into the RIB

Answer 26

1. Longest prefix length /26>/23 2. AD of routing protocol 3. Metric

Question 27

What is the default administrative distance of a connected route

Answer 27

0

Question 28

What is the default administrative distance of a directly connected route

Answer 28

1

Question 29

What is the default administrative distance of EIGRP (Summary route)

Answer 29

5

Question 30

What is the default administrative distance of eBGP

Answer 30

20

Question 31

What is the default administrative distance of EIGRP (internal)

Answer 31

90

Question 32

What is the default administrative distance of OSPF

Answer 32

110

Question 33

What is the default administrative distance of IS-IS

Answer 33

115

Question 34

What is the default administrative distance of RIP

Answer 34

120

Question 35

What is the default administrative distance of EIGRP (external)

Answer 35

170

Question 36

What is the default administrative distance of iBGP

Answer 36

200

Question 37

What is equal cost multi pathing

Answer 37

When 2 routes from the same protocol are presented that have the same metric. Both routes will be entered into the RIB and the traffic will be load balanced across the 2 paths.

Question 38

What dynamic routing protocols support equal cost multi pathing

Answer 38

RIP EIGRP OSPF IS-IS

Question 39

What is un-equal cost multi pathing

Answer 39

When 2 routes from the same protocol are presented that have the different metrics. Both routes can be entered into the RIB and the traffic will be load balanced across the 2 paths. This is not enabled by default.

Question 40

What dynamic routing protocols support equal cost multi pathing

Answer 40

EIGRP

Question 41

What is a directly attached static route

Answer 41

A static route where the next hop is defined as the outgoing interface.

Question 42

What is a recursive static route

Answer 42

A static route where the next hop is defined as the remote link IP address.

Question 43

What is a fully specified static route

Answer 43

a static route where both the outgoing interface and the remote IP are defined.

Question 44

IPv6 uses the same principles for routing as IPv4 True or False

Answer 44

True

Question 44

What is a static null interface

Answer 44

A logical interface that drops all traffic destined for it.

Question 45

What command is needed to enable IPv6 routing

Answer 45

IPv6 unicast routing

Question 46

What is a VRF

Answer 46

A technology that creates multiple virtual routers on 1 physical router.

Question 47

What parameters are separated between VRF instances

Answer 47

Routing tables Router interfaces Forwarding tables

Question 48

What is the default VRF called

Answer 48

Global

Question 49

What is the main advantage of VRFs

Answer 49

Increased network security by separation