Background Flashcards

1
Q

Does layer 1 have a way to communicate from device to device?

A

No, it’s like shouting in a room. Everyone hears/sees communication

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2
Q

Does a device operating at layer 4 have only layer 4 capabilities?

A

No, it has layer 4 and all of the way down.

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3
Q

What is another name for layer 2

A

Data link

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4
Q

What is the most common layer 2 protocol?

A

Ethernet

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5
Q

Addressing protocol in layer 2

A

MAC address

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6
Q

Transmission encapsulation in layer 2

A

Frames

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7
Q

Two parts of a mac address

A

24 bits of manufacturer info
24 bits of uniqueness

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8
Q

Layer 2 Frame mac header includes (3 things)

A

Dest MAC address
Source MAC Address
Layer 3 protocol, typically IP

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9
Q

Difference between hub and switch

A

Hub is layer 1 (collisions and dumb and broadcast)
Switch is layer 2 (MAC address table, store & forward)

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10
Q

IP Address to binary

A
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11
Q

What is another way to think of /16 or /25

A

The number of 1’s in the subnet mask

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12
Q

In a router’s route table, is a more specific route preferred or generic?

A

More specific. /anything more specfic than /0 will be selected.

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13
Q

What is ARP?

A

Address Resolution Protocol, getting MAC addresses for IP Addresses

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14
Q

This device moves packets from source to destination, encapsulating things in new layer 2 frames on the way, using ARP to find the next MAC to IP mapping

A

Router

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15
Q

Two protocols operating at layer 4

A

TCP

UDP

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16
Q

TCP segments are encapsulated in these

A

IP Packets

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17
Q

Do TCP segments have SCR/DST information?

A

No, rely on IP packets for device addressing

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18
Q

What is NAT?

A

Network Address Transalation - Translates source IP address to something else, often private IP to public. Helps with shortage of IPV4 addresses.

19
Q

In static NAT, the router maintains a NAT table and this kind of relationship of internal IP’s to external IPs

A

1:1, each internal source gets a different external IP.

20
Q

Dynamic NAT has a small pool of IP and allocates them in this kind of manner

A

Temporary (if IPs run out, possible a request from a new internal client could fail)

21
Q

Dynamic NAT: What kind of mapping relationship exists from internal to the limited pool of external address?

A

Also 1:1, for the duration of the allocation

22
Q

Port Address Translation creates a NAT table and maps internal devices to external IPs in this way

A

Many internal to 1 External, also mapping to new client ports to avoid collision

23
Q

2 Common examples of Port Address Translation

A

Home routers

AWS NAT Gateway

24
Q

AWS Example of Static NAT implementation

A

Internet Gateway (IGW)

25
Q

Class A Address space

A
  1. 0.0.0
  2. 255.255.255
  3. , 1.,2….127.
26
Q

Class B address space

A
  1. 0.0.0
  2. 255.255.255
  3. 1, 128.2…191.254, 191.255
27
Q

Class C address space

A
  1. 0.0.0
  2. 255.255.255
  3. 0.1, 192.0.2…
28
Q

Class D Address Space

A

Multicast

29
Q

Class E address space

A

Reserved

30
Q

What is a class A non-routable IP address range and how many Class A networks does it contain?

A

10.0.0.0-10.255.255.255

1

31
Q

What is a Class B non-routable IP address range and how many Class B networks does it contain?

A

172.16.0.0-172.31.255.255

16

32
Q

What is a non-routable Class C IP address range and how many class C networks does it have?

A

192.168.0.0-192.168.225.225

256 Class C networks

33
Q

What is 802.1Q?

A

A change to the defaul ethernet frame, it adds a field that is used for VLANs.

34
Q

What is 802.1AD or QinQ?

A

AKA Provider Bridging or Stacked VLANS, adds an additonal ethernet frame on top of 802.1Q.

35
Q

What are the two additional ethernet frames known as 802.1AD (QinQ)?

A

S-TAG, or service(provider), and C-TAG, or Customer

36
Q

VLANS create this type of layer 2 network segments

A

Separate/Isolated

37
Q

VLANS create separate

A

Broadcast Domains (prevents layer 2 broadcast/communication between VLANS)

38
Q

What is the typical size of a jumbo frame?

A

9000 bytes, as opposed to the standard 1500

39
Q

This will happen if you try to use jumbo frames but not all networking equipment on your path supports it

A

fragmentation

40
Q

4 AWS cases that don’t support jumbo frames

A

Traffic outside of a single VPC

Traffic over inter-region VPC peering

Traffic over VPN connections

Traffic over an internet gateway

41
Q

3 AWS use cases that support jumbo frames

A

Same region peering

Direct Connect

Transit Gateway (capped at 8500 bytes)

42
Q

Stegonagraphy

A

Hiding information in something more common. Example:

Encrypt something with destination person public key, embedd info in a puppy image, sned to person, person has the process to remove data from image, decrypt with their private key

43
Q

What is the worst thing someone can do if they have your public key?

A

Use it to encrypt data

44
Q

Four key tenants of modern hashing

A

Every item you put in generates a unique hash

Hashing is repeatable…if I put in the same data, same hash should come out…and can be used to verify something hasn’t been altered

Hashing algorithms are only one way

Without a critical vulnerability, modern hashes aren’t breakable