Background

Question 1

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

Answer 1

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

Question 2

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

Answer 2

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

Question 3

What is another name for layer 2

Answer 3

Data link

Question 4

What is the most common layer 2 protocol?

Answer 4

Ethernet

Question 5

Addressing protocol in layer 2

Answer 5

MAC address

Question 6

Transmission encapsulation in layer 2

Answer 6

Frames

Question 7

Two parts of a mac address

Answer 7

24 bits of manufacturer info
24 bits of uniqueness

Question 8

Layer 2 Frame mac header includes (3 things)

Answer 8

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

Question 9

Difference between hub and switch

Answer 9

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

Question 10

IP Address to binary

Answer 10

Question 11

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

Answer 11

The number of 1’s in the subnet mask

Question 12

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

Answer 12

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

Question 13

What is ARP?

Answer 13

Address Resolution Protocol, getting MAC addresses for IP Addresses

Question 14

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

Answer 14

Router

Question 15

Two protocols operating at layer 4

Answer 15

TCP

UDP

Question 16

TCP segments are encapsulated in these

Answer 16

IP Packets

Question 17

Do TCP segments have SCR/DST information?

Answer 17

No, rely on IP packets for device addressing

Question 18

What is NAT?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

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

Answer 20

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

Question 21

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

Answer 21

Also 1:1, for the duration of the allocation

Question 22

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

Answer 22

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

Question 23

2 Common examples of Port Address Translation

Answer 23

Home routers

AWS NAT Gateway

Question 24

AWS Example of Static NAT implementation

Answer 24

Internet Gateway (IGW)

Question 25

Class A Address space

Answer 25

0. 0.0.0 127. 255.255.255 0. , 1.,2....127.

Question 26

Class B address space

Answer 26

128. 0.0.0 191. 255.255.255 128. 1, 128.2...191.254, 191.255

Question 27

Class C address space

Answer 27

192. 0.0.0 223. 255.255.255 192. 0.1, 192.0.2...

Question 28

Class D Address Space

Answer 28

Multicast

Question 29

Class E address space

Answer 29

Reserved

Question 30

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

Answer 30

10.0.0.0-10.255.255.255 1

Question 31

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

Answer 31

172.16.0.0-172.31.255.255 16

Question 32

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

Answer 32

192.168.0.0-192.168.225.225 256 Class C networks

Question 33

What is 802.1Q?

Answer 33

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

Question 34

What is 802.1AD or QinQ?

Answer 34

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

Question 35

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

Answer 35

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

Question 36

VLANS create this type of layer 2 network segments

Answer 36

Separate/Isolated

Question 37

VLANS create separate

Answer 37

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

Question 38

What is the typical size of a jumbo frame?

Answer 38

9000 bytes, as opposed to the standard 1500

Question 39

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

Answer 39

fragmentation

Question 40

4 AWS cases that don't support jumbo frames

Answer 40

Traffic outside of a single VPC Traffic over inter-region VPC peering Traffic over VPN connections Traffic over an internet gateway

Question 41

3 AWS use cases that support jumbo frames

Answer 41

Same region peering Direct Connect Transit Gateway (capped at 8500 bytes)

Question 42

Stegonagraphy

Answer 42

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

Question 43

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

Answer 43

Use it to encrypt data

Question 44

Four key tenants of modern hashing

Answer 44

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