Fundamentals of WANs

Which of the following are examples of common Internet access links?

HDLC

PPP

DSL

Dial-Up

Correct! Wrong!

When PC1 on an Ethernet network sends a packet to a remote PC2 that is on another Ethernet network, and the packet is routed by exactly two routers, connected by an HDLC WAN connection, how many different Layer 2 headers (with different addresses in the headers) will be created to encapsulate the IP packet as it travels from PC1 to PC2?

None. HDLC doesn’t use Ethernet headers.

1

3

2

4

Correct! Wrong!

How does the receiver of an HDLC frame know what has been encapsulated within that frame?

Based on the FCS field

Based on the Flag field

The Type field in the header

From the IP address (IPv4, IPv6, and so on)

HDLC only encapsulates IPv4

Correct! Wrong!

Fred has just added DSL service at his home, with a separate DSL modem and consumer-grade router with four Ethernet ports. Fred wants to use the same old phone he was using before the installation of DSL. Which is most likely true about the phone cabling and phone used with his new DSL installation?

He uses the old phone, cabled to the DSL modem’s ports.

The old phone must be replaced with a digital phone.

He uses the old phone, cabled to one of the router/switch device’s Ethernet ports.

He uses the old phone, cabled to an existing telephone port, and not to any new device.

Correct! Wrong!

Two routers, R1 and R2, connect using an Ethernet over MPLS service. The service provides point-to-point service between these two routers only, as a Layer 2 Ethernet service. Which of the following are the most likely to be true about this WAN?

R1 will connect to a physical Ethernet link, with the other end of the cable connected to R2

R1 will forward data-link packets to R2 using an Ethernet header/trailer.

R1 will forward data-link frames to R2 using an Ethernet header/trailer.

R1 will forward data-link frames to R2 using an HDLC header/trailer.

Correct! Wrong!

What is the purpose of the FCS field in an HDLC frame?

Used for identifying the type of L3 payload being carried in the frame

Used to indicate to the receiving device that a new frame is arriving

Specifies the destination IP address for the frame

Used for error detection

Identifies the destination L2 address for the frame

Correct! Wrong!

Which of the following Internet access technologies, used to connect a site to an ISP, offers asymmetric speeds?

Leased lines

DSL

Dial-Up

BGP

Correct! Wrong!

Which of the following is an accurate speed at which a leased line can operate in the United States?

100 Kbps

256 Kbps

100 Mbps

8 Mbps

Correct! Wrong!

Which of the following fields in the HDLC header used by Cisco routers does Cisco add, beyond the ISO standard HDLC?

Type

Flag

FCS

Address

Correct! Wrong!

In the cabling for a leased line, which of the following typically connects to a four-wire line provided by a telco?

Router serial interface with internal transceiver

Router serial interface without internal CSU/DSU

CSU/DSU

Switch serial interface

Correct! Wrong!

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Fundamentals of WANs

Which of the following are examples of common Internet access links?

How does the receiver of an HDLC frame know what has been encapsulated within that frame?

Two routers, R1 and R2, connect using an Ethernet over MPLS service. The service provides point-to-point service between these two routers only, as a Layer 2 Ethernet service. Which of the following are the most likely to be true about this WAN?

What is the purpose of the FCS field in an HDLC frame?

Which of the following Internet access technologies, used to connect a site to an ISP, offers asymmetric speeds?

Which of the following is an accurate speed at which a leased line can operate in the United States?

Which of the following fields in the HDLC header used by Cisco routers does Cisco add, beyond the ISO standard HDLC?

In the cabling for a leased line, which of the following typically connects to a four-wire line provided by a telco?