10.1 WAN Types

Question 1

Describe Point-to point WAN topology

Answer 1

A point-to-point connection is a single, pre-established path from the customer’s network through a carrier network (typically an ISP) to a customer’s remote network. A point-to-point line is usually leased from a carrier and thus is often called a leased line.

Question 2

Describe a Hub and Spoke connection WAN topology

Answer 2

A hub and spoke is similar to a point-to-point connection. However, instead of connecting a single remote network, a hub and spoke WAN connects multiple remote networks via WAN links. With a hub and spoke WAN:

- One site is designated as the hub.
- Multiple remote networks (called spokes) are connected to the hub.
- Communications between remote sites is always routed through the hub.

Question 3

Describe a Full mesh WAN Topology

Answer 3

A full mesh WAN topology connects multiple network locations to each other via WAN links. With a full mesh, each location has a direct WAN link to all other locations. This creates a highly redundant WAN topology. However, a full mesh WAN is very expensive, and difficult to establish and maintain.

Question 4

What is a Single-homed WAN Topology

Answer 4

A single-homed WAN is a network connected to an ISP using a single line. Single-homed connections are the most common type of WAN connections.

Question 5

What is a Dual-Homed WAN Topology

Answer 5

A dual-homed WAN provides two separate physical connections to a single ISP. These two connections serve two purposes:
Redundancy: If one of the interfaces goes down, connectivity is retained by the secondary connection.
Increased bandwidth: Outbound traffic can be distributed between the two connections, providing double the bandwidth.

Question 6

Describe a Circuit switching WAN Topology Connection

Answer 6

A circuit switching network allows data connections that can be initiated when needed and terminated when communication is complete. It works much like a telephone line works for voice communication. A circuit switched network uses a dedicated connection between sites. It is ideal for transmitting data that must arrive quickly and in the order it is sent, as is the case with real-time audio and video.

Question 7

Describe a Packet switching WAN Connection

Answer 7

A packet switched network allows data to be broken up into packets and sent across shared resources. Packets are transmitted along the most efficient route to the destination. Packet switching is ideal for transmitting data that can handle transmission delays, as is often the case with web pages and email.

Question 8

Describe a Private type WAN

Answer 8

A private WAN allows a site to connect to one or more designated sites using communication methods that maintain the privacy of the data being transferred.

Question 9

Describe a Public type WAN

Answer 9

A public WAN (e.g., the internet) allows access to any number of sites outside the private network. The communication lines are not protected and the entity initiating the communication is responsible for the security of the data.

Question 10

Describe cellular type networking

Answer 10

Cellular networking uses a digital mobile phone network for internet access.

Question 11

Describe Metro Ethernet

Answer 11

Metro Ethernet, sometimes called a metropolitan area network (MAN), is an Ethernet network that covers an area as small as a few city blocks to as large as an entire metropolitan city. MANs provide a connection to the internet as well as connections to remote locations within the MAN. Most MANs are owned and managed by a city and provided as a public utility. Many IT professionals do not differentiate between a wide area network and a MAN since they use essentially the same network technologies.

Question 12

Describe (DSL) Digital Subscriber line

Answer 12

DSL offers digital communications over what is referred to as plain old telephone service (POTS) lines.

Question 13

Describe Cable WAN connectivity type

Answer 13

Cable internet access is typically offered by companies that provide cable television access. Existing cable TV lines provide bandwidth for internet access in addition to cable TV stations.

Question 14

Describe ISDN

Answer 14

offers digital communications over either existing POTS or T1 lines.

Question 15

Describe VSAT

Answer 15

A very small aperture terminal (VSAT) is a small-sized earth station used in the transmit/receive of data, voice and video signals over a satellite

Question 16

Describe MPLS

Answer 16

MPLS is a high-performance method for forwarding packets through a network. MPLS reduces the number of routing lookups by using labels and label switching to forward packets. Packets are forwarded based on the contents of the label, without examination of the packet. This allows the creation of end-to-end circuits across any type of WAN transport medium, using any protocol.

Question 17

What does a leased line allow you to do

Answer 17

allow you to connect two or more routers together that are separated by a large geographical distance.

Question 18

Describe a leased line

Answer 18

A leased line is a dedicated, always-on circuit between two endpoints. The service provider passes a constant rate bit stream without interpreting or making decisions about the data sent over the circuit. A physical leased line WAN works similarly to an Ethernet crossover cable connecting two routers; however, there is no distance limitation. Layer 1 leased lines are sometimes referred to using the following names:
A leased circuit
A serial link
A point-to-point link
T1 line
A generic WAN link

Question 19

Name the facts about leased lines

Answer 19

Each router runs in full-duplex.
The speed is symmetric, meaning that both routers send bits at the same speed.
The lease line provides a physical layer bit transmission facility:
Routers require a data link protocol on the WAN link.
The lease line itself does not define a data link layer protocol to be used.

Question 20

Describe (HDLC) High-Level Data Link Control Protocol

Answer 20

HDLC is often used as the data link protocol for WAN leased line connections:
Cisco routers run HDLC by default.
When implementing HDLC, administrators must do the following for each interface:
Configure the IP address.
Ensure that no other layer 2 encapsulation protocol is configured on the interface.
HDLC organizes data into frames.
HDLC controls the pace at which data is transmitted.
The HDLC frame header identifies the frame type to the router.
The HDLC trailer has a Frame Check Sequence (FCS) field that the receiving router can use to verify the frame. The FCS field allows Cisco routers to support multiple types of Network layer packets to cross an HDLC link.

Question 21

Describe CPE

Answer 21

Customer Premise Equipment (CPE) is the equipment at the customer site.

Question 22

Describe CSU/DSU

Answer 22

Leased lines require a CSU/DSU device that provides the clocking function. Clocking physically controls the speed and timing that the router’s serial interfaces send and receive bits over the serial cable. The CSU:
Sits between the telecommunication lease line and the router.
Understands the layer 1 conventions of both the telecommunication equipment and the router.
Must be configured to match the telecommunication speed settings.
Connects to the router with the DCE and DTE roles.

Question 23

Describe Serial Cable

Answer 23

The serial cable connects the router to the CSU:
The serial cable is usually a short cable.
Serial interfaces on the router are typically a removable card called a WAN interface card (WIC).
The correct cable type must be used to connect the WIC with the CSU/DSU.
New WICs have CSU/DSU capability built-in.

Question 24

Describe Supported lines

Answer 24

Types of lines supported are:
DS1 or T1 transmitting up to 1.544 Mbps.
Fractional T1 working in multiples of 64 kbps.
Fractional T3 working in multiples of 1.536 Mbps.
DS3 or T3, traditionally referred to as a 45 Mb pipe, or 44.736 Mbps.

Question 25

router(config-if)#clock rate [rate]

Answer 25

Sets the clock rate on the DCE serial interface. The rate should be set in bits per second (bps). In the back-to-back router lab configuration, if the clock rate command is not issued on the DCE, clocking is not provided and the interface status between the two routers will not change to up.

Question 26

router(config-if)#ip address [address] [mask]

Answer 26

Assigns an IP address and subnet mask to the interface.

Question 27

router(config-if)#encapsulation hdlc
router(config-if)#encapsulation ppp
router(config-if)#encapsulation frame-relay

Answer 27

Modifies the router encapsulation method.

Question 28

router#sh interfaces

Answer 28

Displays all interface configurations, including serial connection encapsulation and bandwidth.

Question 29

router#sh ip int brief

Answer 29

Displays a consolidated message about each IP interface, including its IP address, line and protocol status, and how the address was configured (DHCP or Manual).

Question 30

router#sh run

Answer 30

Displays the clock rate and bandwidth of a serial configuration.

Question 31

router#sh controllers [serial interface]

Answer 31

Displays the serial interface configuration, such as the type of serial cable and which end of the cable is connected to the device, DCE or DTE.