IP Routing

Question 1

Address Resolution Protocol (ARP)

Answer 1

A procedure for mapping an IP address to a physical MAC address in a local area network (LAN). ARP uses broadcast messages to query unknown addresses, using the information to build the ARP Table.

Question 2

Address Resolution Protocol (ARP) Table

Answer 2

A table kept on a router that contains lists of IP-to-MAC address mappings, providing Layer 3 to Layer 2 address resolution.

Question 3

Administrative Distance (AD)

Answer 3

A feature that routers use in order to select the best path for traffic when there are two or more routes to the same destination. The router will choose the route with the lowest administrative distance (AD) when multiple paths are possible.

Question 4

(OSPF) Area

Answer 4

A grouping of router interfaces participating in OSPF that share a common view of the area, used to map out the topology. This information is stored in each router’s OSPF Link State Database (LSDB)

Question 5

Area Border Router (ABR)

Answer 5

A router with at least two interfaces participating in OSPF that connect to different areas.

Question 6

Autonomous System (AS)

Answer 6

A network or group of networks that are within a single routing domain.

Question 7

Connected Route

Answer 7

A route that is physically connected to an interface on a router. Directly connected routes have an administrative distance (AD) of 0.

Question 8

Default Gateway

Answer 8

The router in a local area network (LAN) used to forward all traffic that is not addressed to a node within the local subnet.

Question 9

Dijkstra Algorithm

Answer 9

The mathematical algorithm used by OSPF to calculate the shortest path between two networks by considering the cost of each link in the area, along with the topology of the area.

Question 10

Distance-Vector

Answer 10

A category of routing protocols in which each router computes the distance between itself and each of its immediate neighbors.

Question 11

Distance-Vector Protocol

Answer 11

A routing protocol that utilizes distance to decide the best packet forwarding path. Examples include Routing Information Protocol (RIP) and Enhanced Interior Gateway Routing Protocol (EIGRP).

Question 12

Exterior Gateway Protocol (EGP)

Answer 12

A routing protocol used to route between Autonomous Systems (AS), such as Border Gateway Protocol (BGP)

Question 13

Floating Static Route

Answer 13

Static routes that have an administrative distance (AD) manually configured greater than the default value of 1, which can be used to provide a backup link for an existing route.

Question 14

Hop Count

Answer 14

The number of devices data must travel through between the source and destination.

Question 15

Interior Gateway Protocol (IGP)

Answer 15

A routing protocol used to route inside an Autonomous System (AS), such as EIGRP or OSPF.

Question 16

Link State Acknowledgement (LSAck)

Answer 16

Used by a router to confirm it received a Link State Update (LSU).

Question 17

Link State Advertisement (LSA)

Answer 17

Information a router sends and receives about network reachability, used to construct a router’s Link State Database.

Question 18

Link State Database (LSDB)

Answer 18

Used by OSPF to store information about the current network topology, which is build using Link State Advertisements (LSAs).

Question 19

Link State Request (LSR)

Answer 19

Used by a router to request specific Link State Advertisement (LSA) information from a neighbor.

Question 20

Link State Update (LSU)

Answer 20

A packet that carries Link State Advertisement (LSA) information.

Question 21

Link-State

Answer 21

A category of routing protocols in which each router shared knowledge of its neighbors with every other router in the network.

Question 22

Link-State Protocol

Answer 22

A routing protocol build around the Dijkstra algorithm, used to determine the shortest packet forwarding path between two points. Open Shortest Path First (OSPF) is the most popular example of this in use today.

Question 23

OSPF Adjacency

Answer 23

An OSPF adjacency is formed two neighbor routers exchange Link State Updates (LSUs) and Database Description (DD) packets so that both routers have identical knowledge of the network.

Question 24

OSPF Backbone Area (Area 0)

Answer 24

The core of an OSPF network to which all other OSPF areas are connected. All routing between areas is distributed through the backbone area.

Question 25

OSPF Broadcast Network

Answer 25

An OSPF network with two or more routers having interfaces in the same subnet, where neighbors are dynamically discovered through multicast Hello messages. This is the default OSPF network type for any Ethernet interface, where DR and BDR are elected.

Question 26

OSPF Dead Interval

Answer 26

The interval that OSPF will wait to receive hello packets from a neighbor before declaring the neighbor as being down (dead). By default the OSPF dead interval is 40 seconds, with the rule of thumb being that the dead interval should be four times the hello interval.

Question 27

OSPF Hello

Answer 27

A protocol used to discover OSPF neighbors and confirm reachability to those neighbors, and also used in the election of a Designated Router (DR). The default interval between hello messages in OSPF is 10 seconds.

Question 28

OSPF Neighbor

Answer 28

An OSPF neighbor is formed when two routers have interfaces that reside on the same subnet. These routers will exchange Hello messages to form a neighborship.

Question 29

OSPF Point-to-Point Network

Answer 29

An OSPF network where two devices are connected together with a single link. With point-to-point links, OSPF does not elect a DR or BDR. This is the default OSPF network type on a non-Frame Relay serial interface.

Question 30

Path-Vector

Answer 30

A category of routing protocols used for routing between autonomous systems (AS), where routes are measured by the number of AS hops required for data delivery.

Question 31

Path-Vector Protocol

Answer 31

A routing protocol with the ability to analyze each hop of the data path, used primarily with routing between Autonomous Systems (AS). Border Gateway Protocol (BGP) is the most well-known example of this in use.

Question 32

Preempt

Answer 32

In a first hop redundancy protocol configuration, this option enables the router with the highest priority to immediately become the active router.

Question 33

Round-Robin

Answer 33

A method of load-balancing in GLBP that equally distributes traffic among all members of a group.

Question 34

Routing Table

Answer 34

A set of rules maintained on a router which are used to determine where data packets will be directed.

Question 35

Static Default Route

Answer 35

A manually created route that specifies the router should use the default route if a more specific path to an IP address destination is not available in the IP routing table.

Question 36

Static Route

Answer 36

A routing entry that is manually configured in a router, rather than having the route information learned dynamically. This allows routers to learn about a route to a remote network that is not directly connected to one of its interfaces. Static routes have an administrative distance (AD) of 1 by default.

Question 37

Type 1 LSA

Answer 37

Also known as a Router LSA, these are generated by each router and contain information about that router’s directly attached networks.

Question 38

Type 2 LSA

Answer 38

Also known as a Network LSA, these are generated for each transit network within an area on which a DR is elected.

Question 39

Type 3 LSA

Answer 39

Also known as a Summary LSA, these are sent from one area to another, used to advertise a network in the source area.