N10-007.3

Question 1

Route Redistribution

Answer 1

Allows routes learned by one routing protocol to be injected into the routing process of another routing protocol.

Question 2

Protocol Independent Multicast (PIM)

Answer 2

A multicast protocol used between multicastenabled routers to construct a multicast distribution tree.

Question 3

Port Address Translation (PAT)

Answer 3

A variant of NAT in which multiple inside local IP addresses share a single inside global IP address. PAT can distinguish between different flows based on port numbers.

Question 4

Poison Reverse

Answer 4

This feature of a distance-vector routing protocol causes a route received on one interface to be advertised back out of that same interface with a metric considered to be infinite.

Question 5

Link-state Advertisement (LSA)

Answer 5

Sent by routers in a network to advertise the networks the routers know how to reach. Routers use those LSAs to construct a topological map of a network. The algorithm run against this topological map is Dijkstra’s shortest path first algorithm.

Question 6

Network Address Translation (NAT)

Answer 6

Allows private IP addresses (as defined in RFC 1918) to be translated into Internet-routable IP addresses (public IP addresses).

Question 7

Static NAT (SNAT)

Answer 7

A variant of NAT in which an inside local IP address is statically mapped to an inside global IP address. SNAT is useful for servers inside a network that need to be accessible from an outside network.

Question 8

Hold-down Timers

Answer 8

Can speed the convergence process of a routing protocol. After a router makes a change to a route entry, the hold-down timer prevents subsequent updates for a specified period of time. This approach can help stop flapping routes (which are routes that oscillate between being available and unavailable) from preventing convergence.

Question 9

Internet Group Management Protocol (IGMP)

Answer 9

A multicast protocol used between clients and routers to let routers know which of their interfaces has a multicast receiver attached.

Question 10

Link State

Answer 10

A category of routing protocol that maintains a topology of a network and uses an algorithm to determine the shortest path to a destination network.

Question 11

Exterior Gateway Protocol (EGP)

Answer 11

A routing protocol that operates between autonomous systems, which are networks under different administrative control. Border Gateway Protocol (BGP) is the only EGP in widespread use today.

Question 12

Administrative Distance

Answer 12

A routing protocol’s index of believability. Routing protocols with a smaller AD are considered more believable than routing protocols with a higher AD.

Question 13

Default Static Route

Answer 13

A default static route is an administratively configured entry in a router’s routing table that specifies where traffic for all unknown networks should be sent.

Question 14

Open Shortest Path First (OSPF)

Answer 14

A link-state routing protocol that uses a metric of cost, which is based on the link speed between two routers. OSPF is a popular IGP because of its scalability, fast convergence, and vendor interoperability.

Question 15

Border Gateway Protocol (BGP)

Answer 15

The only EGP in widespread use today. In fact, BGP is considered to be the routing protocol that runs the Internet, which is an interconnection of multiple autonomous systems. BGP is a path-vector routing protocol, meaning that it can use as its metric the number of autonomous system hops that must be transited to reach a destination network, as opposed to the number of required router hops.

Question 16

Distance Vector

Answer 16

A category of routing protocol that sends a full copy of its routing table to its directly attached neighbors.

Question 17

Frame Relay

Answer 17

A Layer 2 WAN technology that interconnects sites using virtual circuits. These virtual circuits are identified by locally significant data-link connection identifiers (DLCIs).

Question 18

Circuit-Switched Connection

Answer 18

A connection that is brought up on an as-needed basis. A circuit-switched connection is analogous to a phone call, where you pick up a phone and dial a number, and a connection is established based on the number you dial.

Question 19

Synchronous Optical Network (SONET)

Answer 19

A Layer 1 technology that uses fiber-optic cabling as its media. Because SONET is a Layer 1 technology, it can be used to transport various Layer 2 encapsulation types, such as ATM. Also, because SONET uses fiber-optic cabling, it offers high data rates, typically in the 155Mbps–10Gbps range, and long-distance limitations, typically in the 20 km–250 km range.

Question 20

Optical Carrier (OC)

Answer 20

Optical networks often use OC levels to indicate bandwidth.

Question 21

Dedicated Lease Line

Answer 21

A logical connection interconnecting two sites. This logical connection might physically connect through a service provider’s facility or a telephone company’s central office.

Question 22

Asynchronous Transfer Mode (ATM)

Answer 22

A Layer 2 WAN technology that interconnects sites using virtual circuits. These virtual circuits are identified by a pair of numbers, called the VPI/VCI pair. A virtual path identifier (VPI) identifies a logical path, which can contain multiple virtual circuits. A virtual circuit identifier (VCI) identifies the unique logical circuit within a virtual path.

Question 23

Time-Division Multiple Access (TDMA)

Answer 23

A channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots.

Question 24

Label Switch Router (LSR)

Answer 24

Resides inside a service provider’s MPLS cloud and makes frame-forwarding decisions based on labels applied to frames.

Question 25

Code-Division Multiple Access (CDMA)

Answer 25

An example of multiple access, where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies. CDMA is used as the access method in many mobile phone standards.

Question 26

Tip and ring

Answer 26

The red and green wires found in RJ-11 wall jacks, which carry voice, ringing voltage, and signaling information between an analog device (for example, a phone or a modem) and an RJ-11 wall jack.

Question 27

Multiprotocol Label Switching (MPLS)

Answer 27

A WAN technology popular among service providers. MPLS performs label switching to forward traffic within an MPLS cloud by inserting a 32-bit header (which contains a 20-bit label) between a frame’s Layer 2 and Layer 3 headers and making forwarding decisions based on the label within an MPLS header.

Question 28

E1

Answer 28

An E1 circuit contains 32 channels, in contrast to the 24 channels on a T1 circuit. Only 30 of those 32 channels, however, can transmit data (or voice or video). Specifically, the first of those 32 channels is reserved for framing and synchronization, and the seventeenth channel is reserved for signaling (that is, to set up, maintain, and tear down a session).

Question 29

E3

Answer 29

A digital circuit in the same E-carrier family of standards as an E1. An E3 circuit’s available bandwidth is 34.4Mbps.

Question 30

Point-toPoint Protocol over Ethernet (PPPoE)

Answer 30

Commonly used between a DSL modem in a home (or business) and a service provider. Specifically, PPPoE encapsulates PPP frames within Ethernet frames. PPP is used to leverage its features, such as authentication.

Question 31

Microsoft Routing and Remote Access Server (RRAS)

Answer 31

A Microsoft Windows server feature that allows Microsoft Windows clients to remotely access a Microsoft Windows network.

Question 32

Point-to-Point Protocol

Answer 32

A common Layer 2 protocol offering features such as multilink interface, looped link detection, error detection, and authentication.

Question 33

Channel Service Unit/Data Service Unit (CSU/DSU)

Answer 33

Acts as a digital modem that terminates a digital circuit (for example, a T1 or an E1 circuit).

Question 34

Challenge Handshake Authentication Protocol (CHAP)

Answer 34

CHAP performs one-way authentication. However, authentication is performed through a three-way handshake (challenge, response, and acceptance messages) between a server and a client. The three-way handshake allows a client to be authenticated without sending credential information across a network.

Question 35

Multiple-input Multiple-output (MIMO)

Answer 35

MIMO uses multiple antennas for transmission and reception. These antennas do not interfere with one another, thanks to MIMO’s use of spatial multiplexing, which encodes data based on the antenna from which the data will be transmitted. Both reliability and throughput can be increased with MIMO’s simultaneous use of multiple antennas.