GOOGLE IT SUPPORT PROFESSIONAL CERTIFICATE
Course 2 – The Bits and Bytes Of Computer Networking
Week 2: The Network Layer
Coursera Study Guide
TABLE OF CONTENT
- PRACTICE QUIZ: THE NETWORK LAYER
- PRACTICE QUIZ: SUBNETTING
- PRACTICE QUIZ: ROUTING
- GRADED QUIZ: ROUTING PATHS AND SUBNETS
- GRADED QUIZ: THE NETWORK LAYER
In the second week of this course, we’ll explore the network layer in more depth. We’ll learn about the IP addressing scheme and how subnetting works. We’ll explore how encapsulation works and how protocols such as ARP allow different layers of the network to communicate. We’ll also cover the basics of routing, routing protocols, and how the Internet works. By the end of this module, you’ll be able to describe the IP addressing scheme, understand how subnetting works, perform binary math to describe subnets, and understand how the Internet works.
- Describe the IP addressing scheme.
- Describe how subnetting works.
- Describe subnets by performing basic math in binary.
- Demonstrate how encapsulation works.
- Describe how ARP protocols allow different layers of the network to communicate.
- Describe how the Internet works.
- Understand the basics of routing and routing protocols.
PRACTICE QUIZ: THE NETWORK LAYER
1. Please select all of the valid IP addresses. Check all that apply.
- 192.168.1.1 (CORRECT)
- 188.8.131.52 (CORRECT)
Nice job! 184.108.40.206 is a valid IP address.
2. How many IP addresses does a class C network have?
- 256 addresses (CORRECT)
- 1 address
- 65,536 addresses
- 16,777,216 addresses
Wohoo! You’re correct.
PRACTICE QUIZ: SUBNETTING
1. What does CIDR stand for?
- Classfull Identification Routing
- Classfull Inter-Destination Routing
- Classless Inter-Domain Routing (CORRECT)
- Classless Internet Destination Routing
Yep! CIDR stands for Classless Inter-Domain Routing.
2. Which of the following is a correct form of CIDR notation?
- 192.168.1.0/24 (CORRECT)
- 192.168.1.0 + 255.255.255.0
Awesome job! CIDR notation uses a forward slash and then lists the numbers of bits in the subnet mask.
3. How many octets does a subnet mask have?
- 4 (CORRECT)
Great work! A subnet mask is the same length as an IP address.
PRACTICE QUIZ: ROUTING
1. Select examples of routing protocols. Check all that apply.
- User Datagram Protocol
- Transmission Control Protocol
- Border Gateway Protocol (CORRECT)
- Hypertext Transfer Protocol
- Routing Information Protocol (CORRECT)
Nice job! You’re correct.
2. Who is permitted to use non-routable address space?
- The IANA
- The IETF
- Anyone (CORRECT)
- It’s for testing purposes only
Awesome! Anyone can use non-routable address space.
3. A typical routing table may contain which of the following? Check all that apply.
- Total hops (CORRECT)
- Destination network (CORRECT)
- Destination address
Way to go! A routing table entry needs to know how many hops away a destination network is.
You nailed it! A routing table entry has to be tied to a specific destination network.
GRADED QUIZ: ROUTING PATHS AND SUBNETS
1. Let’s see how much you’ve learned about routing paths and subnetting! In this activity, you are given a bunch of source and destination IP address pairs. Your task is to route each of these packets from the correct source network to the correct destination network.
Step 1: You will be presented 8 source and destination IP address pairs in the table below.
Step 2: You will mimic how the packets travel from the source IP address to the destination IP address within the network. Click the network source (the corresponding orange bubble) and click all the networks it needs to use in order to reach the destination network. You will need to click each network in the right order.
Step 3: After you’ve selected the source and destination networks, click the “Check” button. Some of these address pairs may not be represented by the networks available. If that’s the case, click the “Source or destination not present” button. If you make a mistake, click the “Reset” button to try again.
Step 4: Once you have correctly answered a question, move on to the next question by clicking on the next question arrow. There are 8 different questions.
Step 5: After you’ve completed all routing paths listed in the table, close the quiz and click the “Submit Quiz” button for a grade.
Question 1 of 8:
Question 2 of 8:
Question 3 of 8:
Question 4 of 8:
Question 5 of 8:
Question 6 of 8:
Question 7 of 8:
Question 8 of 8:
GRADED QUIZ: THE NETWORK LAYER
1. An ARP broadcast is sent to the special MAC address ________.
- FF:FF:FF:FF:FF:FF (CORRECT)
You got it! ARP broadcasts are used to ask all devices on a local area network if they’re associated with a specific IP address.
2. A network device that knows how to forward data along to other networks is known as a ______.
- router (CORRECT)
Right on! A router allows devices on different networks to communicate with each other.
3. TTL stands for _______.
- Taco Tuesday Lunch
- Time To Live (CORRECT)
- Total Time Left
- Technical Telephony Layer
Yep! TTL is used to make sure that an undeliverable packet doesn’t spend all of eternity waiting for delivery.
4. There are ____ octets in an IP address.
- 4 (CORRECT)
Great work! An octet represents eight bits, or one byte.
5. In binary, 1 +1 = _____.
- 10 (CORRECT)
Awesome! Binary addition is just like decimal addition, except you only have two numerals instead of ten.
6. A single octet in an IP address represents what range of decimal numbers?
- 0-255 (CORRECT)
Great work! Eight bits of data, or a single octet, can represent all decimal numbers from 0-255.
7. What information will you find in the 16-bit field in an IP datagram?
- The header length field
- The total length of the datagram it’s attached to (CORRECT)
- The Internet Protocol version
- The quality of service technologies
You got it! The final field is a 16-bit field known as the total length field. It is used to indicate the total length of the IP datagram it’s attached to.
8. What is eight bits of data called?
- Octet (CORRECT)
- Figure eight
You nailed it! Eight bits of data, or a single octet, can represent all decimal numbers from 0-255.
9. Which number cannot be represented by eight bits of data?
- 436 (CORRECT)
Woohoo! Eight bits of data, or a single octet, can represent all decimal numbers from 0-255. 436 is beyond this limit.
10. Which IP address is Class C?
- 220.127.116.11 (CORRECT)
Well done! Class C addresses begin with a first octet value of 192 through 223.
11. What protocol is used to discover the hardware address of a node with a certain IP address?
- CIDR, or Classless Inter-Domain Routing
- ARP table (CORRECT)
- SQL database
- Subnet mask
You got it! An ARP table is just a list of IP addresses and the MAC addresses associated with them.
12. Which octet of the subnet mask 255.255.255.0 will tell the router the corresponding host ID?
- The middle two octets
- The last octet (CORRECT)
- The first octet
- The first and last octet
Well done! The size of a subnet is entirely defined by its subnet mask. So for example, with a subnet mask of 255.255.255.0, we know that only the last octet is available for host IDs, regardless of what the size the network and subnet IDs are.
13. What is the maximum decimal number possible to represent with 16 bits?
- 65536 (CORRECT)
Woohoo! If you have a 16-bit number, you can just perform the math 2^16 which would be 65536 numbers.
14. CIDR simplifies how routers and other network devices need to think about the parts of an IP address, but it also allows for more arbitrary network sizes. What does CIDR stand for?
- Costless Inter-Data Routing
- Classless Inter-Domain Routing (CORRECT)
- Clear Inter-Developer Relations
- Classic Intra-Demo Ratings
Great work! CIDR, or Classless Inter-Domain Routing, expands on the concept of subnetting by using subnet masks to demarcate networks.
15. What type of network address space allows for nodes on a network to communicate with each other, but prevents any gateway router from forwarding traffic there, and are reserved for internal networks?
- Non-routable address space (CORRECT)
- MAC address
- IP address
- Subnet mask
Right on! Non-routable address space allows for nodes on such a network to communicate with each other, but no gateway router will attempt to forward traffic to this type of network.
16. The entirety of a packet at one layer becoming the payload section at another layer is known as ________.
- encapsulation (CORRECT)
Correct: Awesome! Encapsulation occurs at each layer of our network stack, except for the physical layer.
17. The process of taking a large network and splitting it up into many individual and smaller subnetworks is known as ________.
- subnetting (CORRECT)
Correct: Nice job! Subnetting allows for much finer-grained controls of network sizes than the old class system could support.
18. RFC stands for ______.
- Routing Frequency Control
- Request For Comments (CORRECT)
- Realtime Frame Check
- Redundant Frame Controller
Correct: That’s right! RFCs have long been used to help establish agreed-upon standards and protocols.
19. Ranges of IP addresses that anyone can use for their internal networks are known as ______.
- Subnet Masks (INCORRECT)
- Demarcation Points
- Autonomous Systems
- Nonroutable Address Space (CORRECT)
20. In binary, 1 +1 = _____.
- 10 (CORRECT)
Correct: Awesome! Binary addition is just like decimal addition, except you only have two numerals instead of ten.
21. A router is performing basic routing functions. What will be the third step in the transmission of a packet?
- -The router looks up the destination network in its routing table.
- – router receives a packet of data.
- -The router examines the destination IP. (CORRECT)
- -The router forwards the packet.
22. How many bits long is an IP address?
- 32 bits (CORRECT)
- 8 bits
- 256 bits
- 64 bits
Correct: Awesome! IP addresses are 32-bit-long numbers made up of four octets, and each octet is normally described in decimal numbers.
23. Which number cannot be represented by eight bits of data?
- 436 (CORRECT)
Correct: Woohoo! Eight bits of data, or a single octet, can represent all decimal numbers from 0-255. 436 is beyond this limit.
24. QoS services are protocols that allow routers to make decisions about which IP datagram may be more important than others. Which IP header field would QoS details be found?
- Service type field (CORRECT)
- Fragmentation offset field
- Total length field
- Identification field
Correct: Nice job! These 8 bits can be used to specify details about quality of service, or QoS, technologies. The important take away about QoS is that they’re services that allow routers to make decisions about which IP datagram may be more important than others.
25. What is the correct term for the list of IP addresses and the MAC addresses associated with them?
- File transfer protocol (FTP)
- SQL database
- ARP table (CORRECT)
- Directory service
Correct: Awesome! ARP is a protocol used to discover the hardware address of a node with a certain IP address.
26. What is the process of taking a large network and splitting it up into many individual and smaller subnetworks called?
- Cloud computing
- Subnetting (CORRECT)
- Dynamic Host Configuration Protocol (DHCP)
Correct: Nice job! Subnetting is the process of taking a large network and splitting it up into many individual and smaller subnetworks, or subnets.
27. Computer A wants to send some data to computer B. Computer A knows that Computer B is not on its local network, so it sends the packet to the router between Network A and Network B. Based on how many network hops have happened, how much will the TTL field be decremented by?
- 1 (INCORRECT)
- 2 (CORRECT)
28. ARP stands for ______.
- Anonymous Resource Protocol
- Augmented Resolution Picture
- Address Resolution Protocol (CORRECT)
- Aggressive Resource Protection
Correct: Nice job! ARP is used to discover what MAC address is associated with a specific IP address.
29. Interior gateway protocols are used by routers in order to share information within a single ________.
- collision domain
- autonomous system (CORRECT)
- destination network
Correct: Great job! An autonomous system is a group of networks all maintained by the same organization.
30. Using logical operators, 1 AND 0 = _____.
- False (CORRECT)
Correct: Nice job! Using the AND operator, the result is only 1, or true, if both sides are also 1, or true.
31. Calculate how many decimal numbers a 4-bit number can represent.
- 16 (CORRECT)
Correct: Right on! A bit is base two. The calculation of a 4-bit number is 2^4 = 16.
32. What protocol communicates data between routers representing the edges of autonomous systems?
- Exterior gateway (CORRECT)
- Link state
- Interior gateway
Correct: Right on! Exterior gateway protocols are used to communicate data between routers representing the edges of autonomous systems.
33. On a Local Area Network, or LAN, what identification do nodes use to communicate with each other internally?
- Static IP address
- Physical MAC addresses. (CORRECT)
- EIN serial
- Dynamic IP address
Correct: Well done! On a Local Area Network, or LAN, nodes can communicate with each other through their physical MAC addresses. This works well on a small scale.
34. Which is a valid IP address?
- 18.104.22.168 (CORRECT)
Correct: You got it! 22.214.171.124 has the correct notation and does not containany numbers that can’t be represented by a single octet.
35. What is the process of taking a single IP datagram and splitting it up into several smaller datagrams called?
- NAT firewall
- Fragmentation (CORRECT)
- Load balancing
Correct: Great work! Fragmentation is the process of taking a single IP datagram and splitting it up into several smaller datagrams.
36. What is the purpose of an ARP response?
- To prevent a flood of UDP packets
- To improve authentication security
- To send an ACK message to the broadcasting computer
- To let a computer broadcasting an ARP message know what MAC address to put into the destination hardware address field (CORRECT)
Correct: Right on! The node that wants to send data sends a broadcast ARP message to the MAC broadcast address which is all F’s. When the network interface receives this ARP broadcast, it sends back what’s known as an ARP response. This response message will contain the MAC address for the network interface in question.
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