unicast routing protocols

Question 1

What does RIP stand for?

Answer 1

Routing Information Protocol

RIP is an intra-domain routing protocol used inside an autonomous system.

Question 2

What type of routing does RIP use?

Answer 2

Distance vector routing

RIP implements distance vector routing directly with some considerations.

Question 3

In RIP, what is the metric used to determine distance?

Answer 3

Hop count

The distance is defined as the number of links that must be traversed to reach the destination.

Question 4

What is the maximum hop count allowed in RIP?

Answer 4

15 hops

Infinity is defined as 16 in RIP.

Question 5

What does the next node column in a RIP routing table represent?

Answer 5

The address of the router to which the packet is to be sent

This is essential for reaching the destination network.

Question 6

What are the two types of messages in RIP?

Answer 6

Request and Response

Requests are sent by routers that have just come up or have time-out entries.

Question 7

What is a solicited response in RIP?

Answer 7

A response sent only in answer to a request

It contains information about the destination specified in the corresponding request.

Question 8

What is the purpose of the expiration timer in RIP?

Answer 8

Governs the validity of a route

If no update is received within 180 seconds, the route is considered expired.

Question 9

How long is the garbage collection timer in RIP set for?

Answer 9

120 seconds

This timer is set for a route after it becomes invalid before purging it from the table.

Question 10

What is the main difference between RIP version 1 and version 2?

Answer 10

Classful versus classless addressing

RIPv1 uses classful addressing while RIPv2 supports classless addressing.

Question 11

What is a link state packet (LSP)?

Answer 11

A packet created by each node containing the state of its links

LSPs carry information necessary for building the topology.

Question 12

What algorithm does link state routing use to build a routing table?

Answer 12

Dijkstra algorithm

This algorithm is used to find the shortest path in the network.

Question 13

What is the role of area border routers in OSPF?

Answer 13

Summarize information about the area and send it to other areas

They connect different areas within an autonomous system.

Question 14

What is the backbone in OSPF?

Answer 14

A special area that connects all other areas in an autonomous system

It serves as the primary area for routing information.

Question 15

What is the well-known port assigned to RIP in UDP?

Answer 15

Port 520

RIP messages are encapsulated in UDP user datagrams.

Question 16

What is the purpose of the periodic timer in RIP?

Answer 16

Controls the sending of messages

This timer is set to a random number between 25 and 35 seconds.

Question 17

What happens when a node receives an older LSP during flooding?

Answer 17

It discards the LSP

The node keeps the newer LSP and sends it out of its interfaces.

Question 18

Fill in the blank: The metric used in RIP is called _______.

Answer 18

hop count

Question 19

True or False: RIP version 2 includes authentication fields.

Answer 19

True

Version 2 includes authentication to protect against unauthorized advertisements.

Question 20

What is the backbone in an autonomous system?

Answer 20

A special area inside an autonomous system where all other areas must be connected.

Question 21

What is the area identification of the backbone?

Answer 21

Zero.

Question 22

What are routers inside the backbone called?

Answer 22

Backbone routers.

Question 23

What must be created if connectivity between a backbone and an area is broken?

Answer 23

A virtual link between routers.

Question 24

What does OSPF allow administrators to assign to each route?

Answer 24

A cost, called metric.

Question 25

What can the metric in OSPF be based on?

Answer 25

* Minimum delay * Maximum throughput

Question 26

What is a link in OSPF terminology?

Answer 26

A connection.

Question 27

Name the four types of links in OSPF.

Answer 27

* Point-to-Point Link * Transient Link * Stub Link * Network Link

Question 28

What characterizes a point-to-point link?

Answer 28

Connects two routers without any other host or router in between.

Question 29

What is a transient link in OSPF?

Answer 29

A network with several routers attached, where data can enter and leave through any router.

Question 30

Why is a transient link described as neither efficient nor realistic?

Answer 30

Each router needs to advertise to multiple neighbors, resulting in excessive advertisements.

Question 31

What is the role of a designated router in a transient link?

Answer 31

To represent the network and reduce neighbor announcements.

Question 32

What is a stub link?

Answer 32

A network connected to only one router.

Question 33

What does a virtual link do?

Answer 33

Connects two routers through a longer path when a direct link is broken.

Question 34

What is the main packet type used in OSPF?

Answer 34

Link state update packet.

Question 35

What does the common header of an OSPF packet define?

Answer 35

* Version * Type * Message length * Source router IP address * Area identification * Checksum * Authentication type * Authentication

Question 36

What is the purpose of the link state update packet?

Answer 36

To advertise the states of a router's links.

Question 37

What do LSAs in OSPF stand for?

Answer 37

Link State Advertisements.

Question 38

What type of information does a router link LSA provide?

Answer 38

Information about all of its links and neighbors.

Question 39

What is the role of a network link LSA?

Answer 39

To announce the existence of all routers connected to a network.

Question 40

What does the summary link to network LSA do?

Answer 40

Announces the existence of other networks outside the area.

Question 41

What must a router inside an area know to send a packet outside the autonomous system?

Answer 41

The route to an autonomous boundary router.

Question 42

What is the function of the external link LSA?

Answer 42

To provide information about networks available outside the autonomous system.

Question 43

What is the purpose of the hello message in OSPF?

Answer 43

To create neighborhood relationships and test reachability of neighbors.

Question 44

What fields are included in the hello packet?

Answer 44

* Network mask * Hello interval * E flag * T flag * Priority * Dead interval * Designated router IP address * Backup designated router IP address * Neighbor IP address

Question 45

What does the database description packet contain?

Answer 45

An outline of the database information.

Question 46

What is the first step in link state routing?

Answer 46

Greeting neighbors with hello packets.

Question 47

What does a newly connected router send after receiving a database description message?

Answer 47

One or more link state request packets ## Footnote This is to obtain full information about particular links.

Question 48

What does the database description packet provide?

Answer 48

An outline of the database information ## Footnote It includes the title of each line in the database.

Question 49

What roles do routers take when exchanging database description packets?

Answer 49

Master and Slave

Question 50

What is the purpose of the E flag in OSPF packets?

Answer 50

Indicates if the advertising router is an autonomous boundary router

Question 51

What does the B flag signify in OSPF packets?

Answer 51

Indicates if the advertising router is an area border router

Question 52

What does the I flag represent in OSPF packets?

Answer 52

Initialization flag

Question 53

What does the M flag indicate in OSPF packets?

Answer 53

More flag, indicating this is not the last message

Question 54

What does the M/S flag denote in OSPF packets?

Answer 54

Indicates the origin of the packet: master or slave

Question 55

What information does the message sequence number field contain in OSPF packets?

Answer 55

The sequence number of the message

Question 56

What is the link state request packet used for?

Answer 56

To request information about specific routes

Question 57

What is the acknowledgment packet's purpose in OSPF?

Answer 57

To acknowledge receipt of OSPF packets

Question 58

True or False: OSPF packets are encapsulated in IP datagrams.

Answer 58

True

Question 59

How many types of packets does OSPF use?

Answer 59

Five different types

Question 60

What is path vector routing used for?

Answer 60

Interdomain routing

Question 61

What does a router maintain in distance vector routing?

Answer 61

A list of networks reachable within the same AS with corresponding costs

Question 62

What must each AS have to provide information to other ASs?

Answer 62

At least one path vector routing that collects reachability information

Question 63

What are the three categories of autonomous systems?

Answer 63

* Stub * Multihomed * Transit

Question 64

What defines a stub AS?

Answer 64

Has only one connection to another AS

Question 65

What is the characteristic of a multihomed AS?

Answer 65

Has more than one connection to other ASs

Question 66

What distinguishes a transit AS?

Answer 66

Allows transient traffic

Question 67

What type of addresses does BGP use?

Answer 67

Classless interdomain routing addresses

Question 68

What are the two broad categories of BGP path attributes?

Answer 68

* Well-known * Optional

Question 69

What is a well-known mandatory attribute in BGP?

Answer 69

ORIGIN

Question 70

What is the purpose of the AS_PATH attribute?

Answer 70

Defines the list of autonomous systems to reach the destination

Question 71

What is the function of the NEXT-HOP attribute?

Answer 71

Defines the next router for packet forwarding

Question 72

What are the two types of BGP sessions?

Answer 72

* External BGP (E-BGP) * Internal BGP (I-BGP)

Question 73

What message is sent to establish a neighborhood relationship in BGP?

Answer 73

Open message

Question 74

What does the keepalive message signify in BGP?

Answer 74

That the routers are still alive

Question 75

What is the purpose of the update message in BGP?

Answer 75

To withdraw destinations, announce new routes, or both

Question 76

What does the notification message in BGP indicate?

Answer 76

An error condition or a request to close the connection

Question 77

True or False: BGP messages are encapsulated in TCP segments using port 179.

Answer 77

True