Module 3: Networking Devices

Question 1

What does a network adapter do?

Answer 1

Also called a network interface card, or NIC, connects a host to the network medium. It is responsible for converting binary data into a format that can be sent on the network medium.

Question 2

What does a transceiver do?

Answer 2

It’s responsible for converting digital data into digital signals to be sent on the medium. The type of signal the transceiver sends depends on the type of network. A fiber optic NIC sends light signals, a wired NIC sends electronic signals on a wire, and a wireless NIC sends radio signals. To receive signals, the transceiver converts digital signals from the network to digital data for the PC.

Question 3

What does a modem do?

Answer 3

Converts binary data to analog waves on the sending end (modulation) and then converts the analog waves back to binary data on the receiving end (demodulation).

Question 4

Network adapters use what layers of the OSI model?

Answer 4

layers 1 and 2.

Question 5

True or False:

The type of network adapter you choose must match the network architecture you are connecting to.

Answer 5

True.

Question 6

Describe a GBIC Transceiver module.

Answer 6

A GBIC (gigabit interface converter) is a large transceiver that fits in a port slot and is used for Gigabit media, including copper and fiber optic.

Question 7

Describe a SFP Transceiver module.

Answer 7

An SFP (small form-factor pluggable) is similar to a GBIC, but is a smaller size. An SFP is sometimes called a mini-GBIC.

Question 8

Describe a SFP+ Transceiver module.

Answer 8

SFP+ is a newer version of the SFP. SFP+ supports data rates as high as 10 Gbit/s, 8 Gbit/s Fibre Channel, 10-gigabit Ethernet, and the Optical Transport Network standard OTU2.

Question 9

Describe a XFP Transceiver module.

Answer 9

An XFP transceiver is similar to an SFP in size, but is used for 10-Gigabit networking.

Question 10

Describe a QSFP Transceiver module.

Answer 10

QSFP (quad, or 4-channel, small form-factor pluggable) is a compact hot-pluggable transceiver that is also used for data communication applications.

Question 11

What is a Media Converter?

Answer 11

• A media converter is used to connect network adapters that are using different media types. For example, a media converter could be used to connect a server with a fiber optic Ethernet NIC to a copper Ethernet cable.
• Media converters only convert from one media type to another within the same architecture (such as Ethernet). A media converter cannot translate between two different architectures. This must be done using a bridge or a router. Converting from one architecture to another would require modifying the frame contents to modify the Data Link layer address.

Question 12

What level does a media converter work at in the OSI model?

Answer 12

Layer 1, the physical layer. Media converters do not read or modify the MAC address in any way.

Question 13

What is a MAC address?

Answer 13

• A MAC address is a unique identifier burned into the ROM of every Ethernet NIC.
• The MAC address is a 12-digit (48-bit) hexadecimal number (each number ranges from 0–9 or A–F).
  The address is often written as 00-B0-D0-06-BC-AC or 00B0.D006.BCAC (dashes, periods, and colons can be used to divide the MAC address parts).
• The MAC address is globally unique by design. The first half of the MAC address, the first six digits, is assigned to each manufacturer. The manufacturer determines the rest of the address, assigning a unique value that identifies the host address. A manufacturer that uses all the addresses in the original assignment can apply for a new MAC address assignment.
• Devices use the MAC address to send frames to other devices on the same subnet.

Question 14

What is an ARP and what does it do?

Answer 14

Stands for Address Resolution Protocol.
- Hosts use ARP to discover the MAC address of a device from its IP address. Before two devices can communicate, they must know the MAC address of the receiving device. If the MAC address isn’t known, ARP does the following to find it:
1. The sending device sends out a broadcast frame.
- The destination MAC address is all Fs
(FFFF:FFFF:FFFF).
- The sending MAC address is its own MAC address.
- The destination IP address is the known IP address
of the destination host.
- The sending IP address is its own IP address.
2. All hosts on the subnet process the broadcast frame, looking at the destination IP address.
3. If the destination IP address matches its own address, the host responds with a frame that includes its own MAC address as the sending MAC address.
4. The original sender reads the MAC address from the frame and associates the IP address with the MAC address, saving it in its cache.

Once the sender knows the MAC address of the receiver, it sends data in frames addressed to the destination device. These frames include a cyclic redundancy check (CRC), which is used to detect frames that have been corrupted during transmission.

Question 15

What is a RARP?

Answer 15

Reversed ARP.

Question 16

What is a Hub?

Answer 16

A hub is the central connecting point of a physical star, logical bus topology. Hubs manage communication among hosts using the following method:

• A host sends a frame to another host through the hub.
• The hub duplicates the frame and sends it to every host connected to the hub.
• The host to which the frame is addressed accepts the frame. Every other host ignores the frame.

Question 17

What layer of the OSI model does a Hub operate on?

Answer 17

Layer 1. It simply repeats the incoming frames without examining them.

Question 18

What is a Bridge?

Answer 18

A bridge is a device that connects two (or more) media segments on the same subnet, and it filters traffic between both segments based on the MAC address in the frame. A bridge builds a database based on MAC addresses to use for making forwarding decisions.

• The process begins by examining the source MAC address of an incoming frame. If the source address is not in the forwarding database, an entry for the address is made in the database, associating the MAC address with the media segment.
• The destination address is then examined:
  
  • If the destination address is not in the database, the frame is sent out on all segments except for the one on which it was received.
  • If the destination address is in the database, the frame is forwarded to the appropriate segment if the segment is different from the one on which it was received.
  • Broadcast frames are forwarded to all segments except the one on which they were received.

Question 19

True or False:

All segments connected to a bridge are on separate subnets.

Answer 19

False. They are on the same subnet and share a common subnet address.

Question 20

Which layer of the OSI model do Bridges operate on?

Answer 20

The are Layer 2 devices; They read the MAC address contained in a frame to make a forwarding decisions.
- Frame forwarding happens independently of the upper-layer protocols (such as TCP/IP).

Question 21

What is a Switch?

Answer 21

A switch is a multi-port bridge that performs filtering based on MAC addresses and provides additional features not found in a bridge.

• While most bridges can process only a single frame at a time, switches can process multiple frames simultaneously.
• Switches offer guaranteed bandwidth to each switch port.
• Switches can make additional forwarding decisions based on the MAC address. For example, a switch can be configured to accept frames from specific MAC addresses.
• Unmanaged switches are autonomous in their function, requiring no port management or configuration. Managed switches allow administrators to change the port configurations, including the following:
  
  • Port speed
  • Duplexing
  • Filters based on network adapter MAC addresses
  • VLAN assignment

Question 22

What layer of the OSI model do Switches operate on?

Answer 22

They are Layer 2 devices, just like bridges.

Question 23

What are WAPs?

Answer 23

Wireless Access Points.
A wireless access point (AP) is a hub for a wireless network.
- As with a hub, any message sent to any wireless host connected to the AP can be received by all other wireless hosts.
- An AP is a Layer 2 device; it can read the Data Link layer address in a frame.
- An AP is often configured as a bridge, connecting a wireless segment to a wired segment. Both wireless and wired hosts are on the same subnet.
- Some APs are combination devices that include a wired switch and even a router.

Question 24

At which layer does a router operate on?

Answer 24

Layer 3, the Network.

Question 25

What is a router?

Answer 25

A router is a device that connects two or more network segments or subnets. - subnet has a unique logical network address. - Routers can be used to connect subnets within a single LAN, or they can be used as gateways to connect multiple LANs together. - Routers can be used to connect networks with different architectures (for example, connecting an Ethernet network to a token ring network).

Question 26

What is a Firewall?

Answer 26

A firewall is a router with additional security features. Firewalls can be programmed with security rules to restrict the flow of traffic between networks. Firewall rules control the type of traffic allowed into a network and the type of traffic allowed out of a network. A firewall can be either hardware devices or software installed onto operating systems.

Question 27

How does a router work?

Answer 27

Routers maintain information about other networks in a database called a routing table. The routing table typically contains the address of all known networks and the next router in the path used to reach the destination network. The routing table is used in the process of forwarding packets.

Question 28

What is a layer 3 switch?

Answer 28

A Layer 3 switch is capable of reading Layer 3 (network) addresses and routing packets between subnets. A Layer 3 switch often provides better performance than a router, but it does not support as many features as a router.

Question 29

What layer does a firewall work on?

Answer 29

Layer 3, the Network layer.

Question 30

What is the process of sending a message from one host to another on a different network?

Answer 30

1. The sending host prepares a packet to be sent. The host uses its own IP address as the source Network layer address and the IP address of the final receiving device as the destination Network layer address. 2. The sending host creates a frame by adding its own MAC address as the source Physical layer address. For the destination Physical layer address, the host uses the MAC address of the default gateway router. 3. The sending host transmits the frame. 4. The next hop router reads the destination MAC address in the frame. Because the frame is addressed to that router, it processes the frame. 5. The router strips off the frame header and examines the packet destination address. It uses the routing table to identify the next hop router in the path. 6. The router repackages the packet into a new frame. It uses its own MAC address as the source Physical layer address and the MAC address of the next hop router as the destination Physical layer address. 7. The router transmits the frame. 8. The next hop router repeats steps 4 - 7 as necessary until the frame arrives at the last router in the path. 9. The last router in the path receives the frame and checks the destination IP address contained in the packet. 10. Because the destination device is on a directly connected network, the router creates a frame using its own MAC address as the source Physical layer address and the MAC address of the destination device as the destination Physical layer address. 11. The router transmits the frame. 12. The destination device receives the frame. Inside the packet, it finds that the destination Network layer address matches its own IP address, and the source IP address is that of the original sending device.

Question 31

Which layer are IP addresses?

Answer 31

Layer 3, The network address.

Question 32

Which Layer are MAC addresses?

Answer 32

Layer 2, Data link layer.

Question 33

Where are the IP address contained?

Answer 33

The IP header.

Question 34

Where are the MAC addresses contained?

Answer 34

Ethernet frame header.

Question 35

True or False: | Network addresses remain constant as the packet is delivered from hop to hop.

Answer 35

True.