C5. Networking Devices Flashcards

1
Q

What is a network interface card? What kind of connections does it provide?

A

NIC is a card installed on your computer to connect, or interface, your computer to the network. It provides the physical, electrical, and electronic connections to the network media

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2
Q

What layer is the NIC based on?

A

The NIC is a layer 2 device because the information it uses for communication - the MAC address - resides on the Data Link layer

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3
Q

What is the NIC built into?

A

It’s built into a computer motherboard - or it is an expansion card. Either way

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4
Q

What do the NIC LEDs indicate?

A

There typically are a couple of LEDs.

1) One, usually green, is called a link light - it indicates that the Ethernet connection has been established w the device on the other end of the cable; it flickers when the traffic goes back and forth
2) Another is activity LED - tends to flicker constantly; the activity indicates intermittent transmission and reception of frames arriving at the network or leaving it
2) Others are just there to indicate connection speed

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5
Q

What is a hub?

A

A hub is a device that connects all network segments together in a star topology

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6
Q

What layer is a hub?

A

A hub is a layer 1 device - it has no intelligence of its own

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7
Q

How do other devices interface with the network?

A
  • Each network device connects directly to the hub through a single cable and is used to connect multiple devices without segmenting a network.
  • Any transmission received on one port will be sent out to all other ports in the hub, including the receiving pair for the transmitting device - so that CSMA/CD on the transmitter can monitor for collisions
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8
Q

What happens when one station sends a broadcast to a network?

A

All other devices in a network receive it! Based on the addressing found in the frame, only the intended recipient will actually listen to the broadcast message and process it

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9
Q

Why are hubs not recommended for today’s corporate networks?

A

Because any two or more of these connected devices have the potential of causing a collision with one another, which means that the hardware device will create a LAN with the most network traffic collisions

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10
Q

What is a bridge?

A

A bridge is a network device that connects two similar network segments together. Its primary function is to keep traffic separated on either side of the bridge, breaking up collision domains

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11
Q

When is the traffic allowed to pass through the bridge?

A

It’s allowed to pass only if the transmission is intended for a station on the opposite side

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12
Q

Why would you place a bridge on a network?

A

To connect two network segments together or to divide a busy network into two segments

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13
Q

Which layer are bridges on?

A

As bridges use MAC addresses to make forwarding decisions, they are Layer 2 devices

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14
Q

What is a switch?

A

Switches are devices that connect multiple network segments together much like hubs do - but
!) a switch recognizes frames
!!) it pays attention to the source and dest. MAC addresses of the incoming frame as well as the port on which it was received

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15
Q

How does switch interpret/handle its ports?

A

It makes each of its ports a unique, singular collision domain

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16
Q

What does a switch do when it notes that a frame’s final destination happens to be on a segment connected via a different port than the one on which the frame was received?

A

The switch will only forward the frame out from the specific port on which the destination is located

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17
Q

What does a switch do when it can’t figure out the frame’s final destination?

A

It will flood the frame out every port except the one on which the frame port was received

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18
Q

What do unmanaged switches do? What can’t they do?

A

They perform the basic switching process and do not allow you to configure more advanced features like adding an IP address for telenetting to the device

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19
Q

What is a router?

A

A router is a network device used to connect many, sometimes disparate, network segments together, combining them into and INTERnetwork

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20
Q

What can a well-configured router do? How does it do it?

A

It can make intelligent decisions about the best way to get network data to its destination
It gathers the necessary information based on the network performance data

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21
Q

What layer are they on?

A

As routers use IP addresses to make forwarding decisions, they are Layer 3 devices

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22
Q

How are routers analogous to computers?

A

They have their own complex operating systems - you can even think of them as CPUs that are totally dedicated to the process of packet routing.

Due to their complexity, you can configure them to perform the functions of other types of networking devices s.a. firewalls by simply implementing a specific feature within router’s software

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23
Q

What’s the major difference between a router interface and a switch interface?

A

On a switch, you don’t add an IP address since they only read to layer 2, and most of the time, you never even need to configure the switch interface

A router expects an IP address on the interface - it does not have one by default - and a good Layer 3 network design must be considered before installing a router

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24
Q

What is one configuration set on switch ports by default?

A

duplex auto. Don’t touch it

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25
Q

What is the switch configuration that you can and probably should adjust?

A

Speed!

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26
Q

What is the purpose of a router interface?

A

To create and maintain broadcast domains and connectivity of WAN services
Before routers can work, their interfaces must be configured and enabled!

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27
Q

What is a firewall?

A

A firewall is a standalone blackbox or a software implementation (placed on a server or a router) that protects LAN resources from invaders that prowl the internet for unprotected networks while simultaneously preventing all or some of your LAN’s computers from accessing certain devices on the internet

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28
Q

Which OSI layers do firewalls operate on?

A

Multiple kinds! Some can operate up to the application level

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29
Q

What connections do the firewalls have?

A

One to the internet and one to the network

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30
Q

What’s the point of the second firewall and what is it called?

A

Demilitarized zone DMZ is used to connect servers and equipment that can be considered both public and private (s.a. email and web servers)

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31
Q

What are IDS/IPS?

A

Intrusion detection systems are network security appliances that monitor networks and packets for malicious activities

32
Q

What’s the difference between an IDS and an IPS?

A

IDS: monitor mode - simply just records problems

IPS - can work in real time to stop problems as they occur

33
Q

What is a HIDS? Where is it typically implemented?

A

Host-based intrusion detection system implemented on a server

34
Q

What is an access point?

A

An AP is a hub that accepts wireless clients via an analog wireless signal (which was generated from a digital signal sent by the wireless client)

35
Q

On which layer do access points operate?

A

They operate on layer 2

36
Q

What is an extender?

A

It’s a radio and antenna that operates in the same frequency or channel and receives the signal as a station would and then transmits it in the desired direction to clients that are out of reach on the original AP

37
Q

What is a contention method?

A

A method used by wired and wireless environments to arbitrate access to the medium to help prevent collisions or at least recover them from where they occur

38
Q

Describe the CSMA/CA Operation

A
  1. Laptop A has a frame to send to laptop B. Before sending, laptop A must check for traffic in two ways. First, it performs carrier sense, which means it listens to see whether any radio waves are being received on its transmitter.
  2. If the channel is not clear (traffic is being transmitted), laptop A will decrement an internal countdown mechanism called the random back-off algorithm. This counter will have started counting down after the last time this station was allowed to transmit. All stations will be counting down their own individual timers. When a station’s timer expires, it is allowed to send.
  3. If laptop A checks for carrier sense and there is no traffic and its timer hits zero, it will send the frame.
  4. The frame goes to the AP.
  5. The AP sends an acknowledgment back to laptop A. Until that acknowledgment is received by laptop A, all other stations must remain silent. The AP will cache the frame, where it already may have other cached frames that need to be relayed to other stations.
  6. Each frame that the AP needs to relay must wait its turn to send the frame using the same mechanism as the stations. When the frame’s turn comes up in the cache queue, the frame from laptop A will be relayed to laptop B.
  7. Laptop B sends an acknowledgment back to the AP. Until that acknowledgment is received by the AP, all other stations must remain silent.
39
Q

Describe the CSMA/CD operation.

A
  1. When a device needs to transmit, it checks the wire. If a transmission is already under way, the device can tell. This is called carrier sense
  2. If the wire is clear, the device will transmit. Even as it is transmitting, it is performing carrier sense.
  3. If another host is sending simultaneously, there will be a collision. The collision is detected by both devices through carrier sense.
  4. Both devices will issue a jam signal to all the other devices, which indicates to them to not transmit.
  5. Then both devices will increment a retransmission counter. This is a cumulative total of the number of times this frame has been transmitted and a collision has occurred. There is a maximum number at which the device aborts the transmission of the frame.
  6. Both devices will calculate a random amount of time and will wait that amount of time before transmitting again. This calculation is called a random back-off .
  7. In most cases, because both devices choose random amounts of time to wait, another collision will not occur.
40
Q

What does DHCP stand for?

A

Dynamic Host Configuration Protocol Server

41
Q

What do DHCP servers do?

A

They assign IP addresses to hosts.

42
Q

How do DHCP servers assign IPs to hosts?

What happens if the DHCP server isn’t on the same segment as the DHCP client?

A

A DHCP server receives a request for IP information from a DHCP client using a broadcast
If the DHCP server isn’t on the same segment as the DHCP client, the broadcast won’t be received by the server because by default, routers won’t forward broadcasts

43
Q

What does a DHCP client ask for? What does a DHCP server provide?

A

Scope options comprise the informational elements that DHCP servers provide to DHCP clients and include

  • TTL
  • DNS server
  • TFTP server
44
Q

What is one parameter in DHCP server response that’s hugely important in figuring out if you have a DHCP problem?

A

The lease time

45
Q

How is a DHCP server configured to ensure that a host always receives the same IP address?

A

Using a reservation list, made based on the router interface MAC address

46
Q

On what layer does the DHCP protocol operate?

A

It’s an application layer protocol

47
Q

What is a DHCP relay?

A

A feature of DHCP servers that helps to provide addresses from a DHCP server to hosts that aren’t on the same LAN as the DHCP server

  • When this feature is up, a router interface relays the DHCP client requests;
  • Otherwise, the router would receive a DHCP client broadcast and promptly discard it, as a result of which the remote host would never receive an address … unless we add a DHCP server on every broadcast domain
48
Q

What is IPAM?

A

IP address management tools are software products that integrate the management of DHCP and DNS. It is used to plan, track, and manage IP addresses

49
Q

What is a multilayer switch?

A

MLS is a computer networking device that switches on Open Systems Interconnection OSI Layer 2 like an ordinary network switch - that provides routing

50
Q

On which layer does an MLS operate?

A

It operates on layer 3 while still providing 24 collision domains

51
Q

What is another name for the host in all things DNS records?

A

A host is otherwise called an A record

52
Q

What does a host do in DNS?

A

A host resolves hostnames to IP addresses

53
Q

What kind of DNS record resolves IP addresses to hostnames?

A

It’s a pointer record, or PTR. PTRs reside in a reverse lookup zone in the server.

54
Q

What does the MX DNS record stand for and what does it do?

A

MX = mail exchanger; in DNS, it translates mail records. The MX record points to the mail exchanger for a particular host

55
Q

What does the CNAME DNS record stand for and do?

A

A CNAME stands for canonical name - it’s more commonly known as an alias record and allows hosts to have more than one name

56
Q

How does DNS work with DHCP?

A

Host registers their names with the DNS server as they receive their IP address configuration from the DHCP server

57
Q

Where can DNS be located?

A

DNS can be located in the DMZ or inside the intranet

58
Q

What does the DNS contain when placed inside the DMZ?

A

In that case the DNS will only contain the records of the devices placed inside the DMZ

59
Q

What is a proxy server?

A

A proxy server is a type of server that handles its client-machine requests by forwarding them on to other servers while allowing granular control over the traffic between the local LAN and the Internet

60
Q

What happens when a proxy server receives a request?

A

It connects to the specific server that can fulfil the request for the client that wants it

61
Q

On what level does a proxy server operate on?

A

Application layer

62
Q

What does the proxy server cache and what’s the point?

A

Sometimes, when the proxy modifies client’s request or a server’s response to it, it will cache the specific server that would have normally been contacted for the request in case it’s needed another time. This behavior speeds up network’s function, thereby optimizing its performance/

63
Q

Name the two main kinds of proxy servers

A

Web Proxy Server and Caching Proxy Server

64
Q

Web Proxy Server - what is it for?

A

It is a server used to create a web cache - stuff that happens when a website “remembers” you

65
Q

What does a Caching Proxy Server do?

A

A caching proxy server recovers information from a client’s earlier request.

66
Q

What is a Caching Proxy Server good for?

A

They minimize the upstream use of bandwidth and greatly optimize the network performance

67
Q

What are the key advantages of using encryption devices?

A

These devices typically provide more choice of encryption methods and stronger encryption options.
They also offload the respective processes from routers and servers, so that routers and servers could focus on their own thing!

68
Q

What is the benefit of dedicating a device to content filtering?

A

It offloads the same kind of work from routers and servers …

69
Q

What does a modem do?

A

A modem (modulator - demodulator) is a device that modulates an analog carrier signal to encode digital information and demodulates the signal to decode this transmitted information

70
Q

What’s a packet shaper?

A

It’s a device that delays some or all packets to bring them into compliance with your or your company’s traffic profile

71
Q

What does a VPN concentrator do?

A

A VPN concentrator is a device that accepts multiple VPN connections from remote locations.

72
Q

What is a VoIP PBX?

A
  • It’s a device that switches between Voice Over IP (Internet Protocol) users on local lines while allowing all users to share a certain number of external phone lines
  • PBX stands for private branch exchange and this is a private telephone switch that resides on the customer premises - it has a direct connection to the telecommunication provider’s switch. It performs call routing within the internal phone system.
73
Q

What is a VoIP endpoint?

A

It’s a desktop phone system or wireless phone system that is part of the converged network where data and voice traffic is combined

74
Q

How are NGFWs (Next-gen firewalls) different from the traditional firewalls?

A

1) Next-gen firewalls are application-aware, meaning that they can distinguish between specific applications instead of allowing all traffic coming in via typical web ports.
2) They examine packets only once, during the deep packet inspection phase, which is required to detect malware and anomalies

75
Q

What is a VoIP gateway? What ports do they have?

A

It’s a kind of network device that helps to convert voice and fax calls between an IP network and Public Switched telephone network in real time. They typically have at least one Ethernet and telephone port.