Routing Protocols

Question 1

Routing Protocol

Answer 1

A set of rules and processes that routers use to learn routes.

Question 2

Interior Gateway Protocol

Answer 2

A protocol used by routers to share information within a single autonomous network

Question 3

Exterior Gateway Protocol

Answer 3

A protocol used by routers to share information between autonomous networks.

Question 4

Autonomous Network

Answer 4

A network or collection of networks that fall under the control of a single organization.

Question 5

Routing Table

Answer 5

The list of routes that is used to make a decision on where to forward IP packets based on destination IP address.

Question 6

Frame Rewrite

Answer 6

The process of reconstructing a packet to be forwarded to the next hop where the router strips the layer 2 information packet, discards the old frame and encapsulates the packet with a new destination MAC address.

Question 7

Route Sources

Answer 7

Connected Routes

Static Routes

Dynamic Routes

Question 8

Default Route

Answer 8

The route used to forward a packet if a destination IP is unknown.

Question 9

What would occur if the routing table contains more than one route with the same destination?

Answer 9

The most specific route is chosen (longest prefix)

or load balance if the routes have equal subnet lengths.

Question 10

Advantages of Dynamic Routes

Answer 10

Greatly reduces administrative overhead by eliminating the need to create many manual routes.

Fault Tolerant as it can automatically choose an alternative route if a link faills.

Question 11

Distance Vector Protocol

Answer 11

A Dynamic Routing Protocl where route tables are shared with direct neighbors and uses hop count to determine routes.

Question 12

Link State Routing Protocol

Answer 12

A Dynamic Routing Protocol where routers share detailed information about the topology via Link State Adveritisements to create a connectivity map in a Link State Database.

Question 13

Metric

Answer 13

The value used to determine which protocol’s route is preferred.

Question 14

RIP

Answer 14

An old Distance Vector protocol that determined routes via hop count. Has been largely replaced by OSPF.

Multicast: 224.0.0.9

AD: 120

Question 15

EIGRP

Answer 15

A Cisco Proprietary Avanced/Hybrid Distance Vector Protocol. Determined routes via Hop Count but has no Hop Limit and can perform Unequal Cost Load Balancing

Question 16

OSPF

Answer 16

Open Shortest Path First.

A Link State Routing Protocol that determines routes via Dijkstra’s algorithm.

Multicast: 224.0.0.5

AD 110

Question 17

OSPF Area Design Rules

Answer 17

OSPF Areas Must start with Area 0 (Backbone Area)

Must be contiguous (able to reach the backbone via ABRs)

Interfaces must be in the same subnet

Question 18

3 Main Phases of OSPF

Answer 18

1) Establish neighbor relationships with other routers
2) Exchange Database information with neighbors
3) Choose routes via LSDB

Question 19

OSPF RID selection Process

Answer 19

1) Manual RID
2) Highest UP loopback IP
3) Highest UP interface IP

Question 20

Neighbor States

Answer 20

1) Down
2) Init
3) 2Way
4) Exstart
5) Exchange
6) Loading
7) Full

Question 21

Down State

Answer 21

Routers send multicast hello packet hoping to learn about neighbors

Question 22

Init State

Answer 22

Router receives hello response and routers check Neighbor Adjacency requirements

Question 23

2way

Answer 23

Routers become neighbors

Question 24

Exstart

Answer 24

Routers select Master and Slave router based on Highest RID

Question 25

Exchange

Answer 25

Routers share a summary of their LSDB known as DBD (descritpion database)

Question 26

Loading

Answer 26

Routers request LSAs they do not have via sending an LSR, LSU and LSAck

Question 27

Full

Answer 27

Routers’ LSDB are synchronized

Question 28

Neighbor Adjacency Requirements

Answer 28

1) Area Number must match
2) Interfaces must be in the same subnet
3) Hello and Dead timers must match
4) OSPF IDs must be unique
5) Authentication settings must match

Question 29

Designated Router

Answer 29

Router that is elected to be the main router for an area and handle Area LSAs

Question 30

Area

Answer 30

Set of routers sharing the same LSDB

Question 31

Backbone Area

Answer 31

A special OSPF Area to which all other areas much connect to

Question 32

ASBR

Answer 32

Autonomous System Boundary Router;

A router connected to another Autonomous System (ISP)

Question 33

Benefits of MutliArea OSPF

Answer 33

Less information is shared between routers allowing for a smaller LSDB which reduces CPU overhead and bandwidth usage.

Question 34

5 Packet Types in OSPF

Answer 34

Hello Packet

Database Description Packet

Link State Request Packet

Link State Update Packet

Link State Acknowledgement Packet