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CISSP > Networking Fundamentals > Flashcards

Networking Fundamentals Flashcards

1
Q

How do you connect computers to a switch?

A

Connect via ethernet cable and plug in via the ports on the back. The ethernet cables push electrical signals between computers connected to the switch

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2
Q

What came before the switch?

A

The hub

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3
Q

What is a hub?

A

It looks the same as a switch appearance wise. However when the hub receives a message from an IP address (computer) it send it to every computer on the system to check if it belongs to them.

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4
Q

What do packet tracers do? (CISCO packet tracer)

A

Let’s you analyse and visualise the electrical signals as they go across the wire

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5
Q

What is a ping message?

A

Use it in networking to make sure other computers are awake and working. It uses other computers IP addresses.

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6
Q

How does a switch work compared to a hub?

A

It has the same goal as the hub. But The switch only passes the message (electrical signals) on to the correct IP address, it doesn’t broadcast it out.

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7
Q

How does the switch know which devices are sat on its network?

A

Via the MAC address, also known as a layer 2 address. Every single device has a MAC address (can’t be changed). When you connect your device to the switch, it learns the MAC address.

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8
Q

Why doesn’t the switch use the IP address?

A

It can’t event see this number. It’s a layer 2 device so can’t even read IP addresses.

Even if you send something over layer 3 (i.e ping someone else’s IP address) the switch will only ever look at the MAC address of that user. The switch stores all of the source MAC addresses in the network.

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9
Q

How does a wireless access point work?

A

It’s an extension of a switch and connects into the switch via a ethernet cable. Device then connect to the access point via waves.

Access point acts in a very similar way to a hub - it broadcasts out the message to all devices. A ethernet cable is preferred .

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10
Q

Whilst switches let you talk within your network, what does a router do?

A

Lets you communicate across an entirely different network

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11
Q

what is the main job of a router?

A

To connect two different networks.

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12
Q

Why do you need a router instead of connecting the switches of different networks?

A

Because the networks have a completely different set of IP addresses

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13
Q

What is a network generally referring to?

A

Groups of IP addresses (therefore computers) i.e 10.1.5 - 10.1.9 and 12.277 - 12.298

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14
Q

How does the sender know the MAC address of the receiver? The switch can’t read IP addresses, so how can it forward it on?

A

Through ARP. Allows you to see which MAC address belongs to which IP address (layer 2).

When you send a message initially, it broadcasts out to all of the ports and asks which device owns the IP address. It then provides the MAC address to the sender. The sender then know’s the MAC address to send the message.

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15
Q

What are the ports on a swith?

A

They are the physical element - the ethernet cables are plugged into their own individual port.

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16
Q

Example - you own a website that allows you to buy clothes. How did this sit within a network?

A

The website sits on a webserver and like any other device it is is connected to a switch (which in turn is connected to a router)

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17
Q

What happens when you try to connect or send a message to a computer (or server) outside of the network?

A

The sender’s system is configured to know which IP addresses sit on their internal network. If the sender is trying to reach an IP address outside of the network, it needs to go through the gateway (also known as the router).

However in the same way that the sender finds internal MAC addresses, the sender must find the MAC address of the router. The sender sends out an ARP request, which is picked up by the router. The MAC address is then send back to the sender and the message is sent to the router.

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18
Q

What happens when the router receives a message from the switch/sender on a network?

A

It still doesn’t have the receiver’s MAC address, only their IP address. The Router know’s where the set of IP addresses live, so it will broadcast an ARP message again. The ARP message will go to the switch on the other side, who will broadcast it out. The receiver will send their MAC address back through the switch and router. The sender, switch and router now have all of the details they need in order to send the message.

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19
Q

What happens when a user want’s to visit a website to buy something (not just pinging/sending messages)

A

They must have a DNS server configured, which turns the URLs into know IP addresses.

But as the switch can only send messages/requests through MAC addresses, you must get the MAC address of your DNS server by broadcasting out to the known IP address (based on config). Only once you have the MAC address can you communicate with the DNS server and learn the IP address of the URL.

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20
Q

Do you have to get the MAC address from your router and other devices (web server, other laptops) each time?

A

No you don’t need to broadcast out. It remembers and puts it in it’s cache!

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21
Q

How does a router know what’s connected to it?

A

It’s stored the IP ranges and ports that they are connect to in it’s memory/table. It will look at this each time.

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22
Q

What is a network?

A

A group of computers that are linked to share resources, files or allow electronic communications. They can be connected together by cables or Wifi. They are computers that connect themselves in order to communicate.

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23
Q

What is one of the largest networks we use?

A

The internet - a network of nertworks.

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24
Q

What does a server do in a network?

A

Some networks have a server, to act as a central hub for emails, internet access and file storage. It’s a powerful computer. When a computer is connected to a server it’s called a client.

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25
Q

what does a switch do?

A

A switch facilitates a network. Rather than joining your computers up by ethernet, it allows you to scale the network and facilitate communication between computers.

26
Q

What happens if people on two different switches want to communicate?

A

It requires a router

27
Q

What does a router do?

A

They help two different networks to talk. Your switches connect to your routers.

28
Q

How does the internet work?

A

It connects billions of routers together.

29
Q

What’s a modem?

A

A modem modulates and demodulates electrical signals sent through phone lines, coaxial cables, or other types of wiring; in other words, it transforms digital information from your computer into analog signals that can transmit over wires, a

30
Q

What is the IP protocol suite?

A

It is the protocols commonly used by the TCP/IP model and used to communication across networks. TCP/IP are the foundational protocols used in the suite.

IP (internet protocol)
TCP (Transmission control protocol)

31
Q

What is multicasting on a network?

A

data is addressed to multiple computers at once. Helpful for distributing audio/video/broadcasts

32
Q

What is TCP/IP?

A

it refers to an entire suite of communication protocols
It gets it name from the most common protocols - TCP and IP

They drive most of the internet connectivity.

33
Q

TCP/IP protocols can be easily hacked as they were designed for ease of use, not security. How can you secure them?

A

Through a VPN link between systems

34
Q

What protocols can be used to establish VPNs?

A 
PPTP (Point to point tunnelling protocol)
L2TP (Layer 2 Tunelling protocol)
SSH (Secure Shell)
OpenVPN (SSL/TLS Vpns)
IPSec (Internet Protocol SEcurity)
TCP wrappers
35
Q

What are TCP wrappers?

A

Application that serves as a basic firewall - restricting access to ports and resources based on user/system IDs. Port Based access control.

36
Q

Full-duplex connection orientated protocl

A

TCP

37
Q

Simplex connectionless protocl

A

UDP

38
Q

When a communication connection is made between two systems it is done by?

A

using Ports (an address number agreed by both end of the communication)

39
Q

What is a socket?

A

Combination of an IP address and port number - i.e a single IP address supports multiple ports

40
Q

What are well known ports 0-1,023?

A

Ports that have standardised assignments to the services they use - i.e port 80 is HTTP

They are used exclusively by servers only!

41
Q

What are ports 1,024 - 49,151?

A

Registered software ports

42
Q

What are ports 49,152 - 65,535?

A

Ransomware, dynamic or ephemeral ports (They are used only temporary)

43
Q

What is subnetting?

A

Breaking down networks (ranges of IP addresses) into something that is more manageable.

Subnets are used to stop traffic congestion, reduce the time taken to travel between networks.

They can be more effcient in allocation IP addresses and ensuring large batches don’t go unused.

Subnets are usually set up geographically for particular offices, or for particular teams within a business to allow their network traffic to stay within the location.

44
Q

What are IP classes?

A

Within IPV4 IP addresses there are five classes of IP address ranges. Each have a valid range of IP addresses.

45
Q

What is an IP address?

A

a number identifying of a computer or another device on the Internet.

46
Q

How long is an IP address?

A

IPv4 addresses are 32 bits long (four bytes). An example of an IPv4 address is 216.58.216.164

47
Q

How does your computer connect to the internet to send information across it?

A

It asks the router for an (external) IP address and the router speaks with your local ISP to do this. This then continues with the DNS, ARP request process etc.

48
Q

What is a loopback address?

A

it allows a device to send a packet and also receive that packet - it’s vital for debugging and testing

49
Q

What is stored in a data centre?

A

Racks and racks of servers, routers and switches

50
Q

How big are data centres?

A

googles, facebook and third party data centres will be huge. But if you own a website you might have one rack with a server, router and switch!

51
Q

Do all companies have a data centre?

A

No - most will rent space elsewhere!

52
Q

Difference between on-prem and cloud?

A

On-premise means that a company keeps all of this IT infrastructure onsite, which is either managed by themselves or a third-party. With the Cloud it means that it is housed offsite with someone else responsible for monitoring and maintaining it. The cloud still involves a data centre! i.e Azure, AWS, Google cloud.

53
Q

Are any companies fully cloud based?

A

Not normally. It’s normally a combination of cloud, renting space in a data centre and having your own data centre.

54
Q

What is contained on servers within a data centre?

A

Websites, data bases

55
Q

How do your servers connect to switches in the data centre?

A

Through access layer, distribution layer and core layer switches (three tier model)

56
Q

What is North south traffic and east west traffic in data centres?

A

North south - is requesting access to a webserver through the internet and getting a response

East west - the servers in the data centre need to speak to eachother. But we didn’t design the networks like this at the start. Accounts for 80% of traffic in DC however.

57
Q

How can a network be designed to help with east west traffic?

A

Spine leaf design - every top layer switch (leaf switch) will connect to the middle layer switch (spine switch)

58
Q

What is a base station?

A

In the area of wireless computer networking, a base station is a radio receiver/​transmitter that serves as the hub of the local wireless network

59
Q

What does a modem do?

A

A modem modulated and demodulates electrical signals sent through phone lines/coxial cables. It essentially transforms digital information from your computer to analog signals that can travel over the phone wire (and vice versa)

60
Q

What is a VLAN?

A

Any broadcast domain that is isolated (by using a switch) and partitioned at the data link layer (Layer 2)

61
Q

What is a WAN?

A

A computing network that spans across a large geographical area

62
Q

What is a LAN?

A

A computing network that connects computers within a a small area such as an office, street etc.

CISSP (6 decks)

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