Messer - 1. Networking Concepts (Part 2 of 2)

Question 1

Draw Prof. Messer’s binary-to-decimal conversion chart.

Answer 1

128 64 32 16 8 4 2 1
0 0 0 0 0 0 0 0

[You can continue extending this to the left, but not necessary for IP addresses because each part of an IP address is 8 bits = 1 byte = 1 octet.. Put another way, if you add up all the numbers above, you get 255, which is most you can have]

Question 2

Using Prof. Messer’s binary-to-decimal conversion chart, convert 00000010 to decimal.

Answer 2

2

Question 3

Using Prof. Messer’s binary-to-decimal conversion chart, convert 10000000 to decimal.

Answer 3

128

Question 4

Using Prof. Messer’s binary-to-decimal conversion chart, convert 10000010 to decimal.

Answer 4

130

Question 5

Using Prof. Messer’s binary-to-decimal conversion chart, convert 11111111 to decimal.

Answer 5

255

Question 6

Using Prof. Messer’s binary-to-decimal conversion chart, convert 32 to binary.

Answer 6

00100000

Question 7

Using Prof. Messer’s binary-to-decimal conversion chart, convert 63 to binary.

Answer 7

00111111

Question 8

Using Prof. Messer’s binary-to-decimal conversion chart, convert 122 to binary.

Answer 8

01111010

Question 9

192. 168.1.165 is a ________.

255. 255.255.0 is a _______.

Answer 9

IP address (IPv4)
subnet mask

Question 10

What is a Default Gateway?

Answer 10

The node (e.g. router) that allows you to communicate outside of your local subnet.

The node in a computer network using the internet protocol suite that serves as the forwarding host to other networks when no other route specification matches the destination IP address of a packet.

In a home or small office environment, the default gateway is a device, such as a DSL router or cable router, that connects the local network to the Internet.

Question 11

The Default Gateway must be an _____ on the ______.

Answer 11

IP address

local subnet

Question 12

If you want to communicate within a network, you only need a _____ and _______. But if you want to communicate outside a network, you also need _________.

Answer 12

IP address
Subnet Mask
Gateway IP address

Question 13

What is the purpose of a subnet mask?

Answer 13

Divides IP address into two parts that identify host computer and network. (A host will then use the subnet mask to know if destination is on local or remote network.)

[Repeating this question]

Question 14

If your IP address is 192.168.1.165, and your subnet mask is 255.255.255.0, what are your network and host addresses?

Answer 14

Network: 192.158.1.0
Host: 0.0.0.165

Question 15

All devices have a special IPv4 address called a _______, which provides an easy way to self-reference when trouble-shooting.

Answer 15

loopback address

Question 16

Depending on the operating system, loopback addresses can range from _______ to _______. However, some operating systems only recognize _________.

Answer 16

127. 0.0.1
128. 255.255.254
129. 0.0.1

Question 17

How would you use a loopback address to ensure that a TCP/IP stack is working properly on a device.

Answer 17

In that device’s command line, type the following:

ping 127.0.0.1

Question 18

_______ addresses are set aside for future use or testing, and range from _______ to _________.

Answer 18

Reserved

240. 0.0.1
241. 255.255.254

[Not to be confused with private addresses]

Question 19

VIP (or VIPA) stands for _______.

Answer 19

Virtual IP Address

Question 20

What is a Virtual IP Address?

Answer 20

An IP address that doesn’t correspond to an actual physical network interface. Used for network address translation, fault-tolerance, mobility, etc.

Question 21

_____ subnetting has not been used since 1993 because ________. However, knowing subnet _____ is still helpful as a starting point for subnetting.

Answer 21

Classful
not an efficient way of IP addressing
classes

Question 22

Draw a chart with the three main subnet classes you need to know, the leading bits that determine the class of an IP address, and the associated default subnet mask.

Answer 22

Class          Leading Bits         Default Subnet Mask
A                 0xxx (1-126)           255.0.0.0
B                 10xx (128-191)        255.255.0.0
C                 110x (192-223)       255.255.255.0

Question 23

What is the class and default subnet mask of the following IP address?

17.22.90.7

Answer 23

Class A

255.0.0.0

Question 24

What is the class and default subnet mask of the following IP address?

220.10.77.40

Answer 24

Class C

255.255.255.0

Question 25

What is the class and default subnet mask of the following IP address?

165.245.0.1

Answer 25

Class B

255.255.0.0

Question 26

What is the class and default subnet mask of the following IP address?

128.90.10.2

Answer 26

Class B

255.255.0.0

Question 27

What is the class and default subnet mask of the following IP address?

191.77.24.250

Answer 27

Class B

255.255.0.0

Question 28

What is the class and default subnet mask of the following IP address?

192.1.12.5

Answer 28

Class C

255.255.255.0

Question 29

Given an IP address and subnet mask, how do you determine the network address?

Answer 29

This is equal to the first IP address of a subnet, which you can get by setting all host bits to 0 (0 decimal)

Question 30

Given an IP address and subnet mask, how do you determine the first usable host address?

Answer 30

This is simply one number higher than the network address

Question 31

Given an IP address and subnet mask, how do you determine the network broadcast address?

Answer 31

This is the last IP address of a subnet, which you get by setting all host bits to 1 (255 decimal)

Question 32

Given an IP address and subnet mask, how do you determine the last usable host address?

Answer 32

This is simply one number lower than the broadcast address

Question 33

10.74.222.11

For the above IP address, determine the following:
Class
Subnet Mask
Network Address
First Host Address
Broadcast Address
Last Available Host Address

Answer 33

Class: A
Subnet Mask: 255.0.0.0
Network Address: 10.0.0.0 (set all host bits to 0)
First Host Address: 10.0.0.1 (add one)
Broadcast Address: 10.255.255.255 (all host bits set to 1)
Last Available Host Address: 10.255.255.254 (subtract 1)

Question 34

172.16.88.200

For the above IP address, determine the following:
Class
Subnet Mask
Network Address
First Host Address
Broadcast Address
Last Available Host Address

Answer 34

Class: B
Subnet Mask: 255.255.0.0
Network Address: 172.16.0.0 (set all host bits to 0)
First Host Address: 172.16.0.1 (add one)
Broadcast Address: 172.16.255.255 (all host bits set to 1)
Last Available Host Address: 172.16.255.254 (subtract 1)

Question 35

192.168.4.77

For the above IP address, determine the following:
Class
Subnet Mask
Network Address
First Host Address
Broadcast Address
Last Available Host Address

Answer 35

Class: C
Subnet Mask: 255.255.255.0
Network Address: 192.168.4.0 (set all host bits to 0)
First Host Address: 192.168.4.1 (add one)
Broadcast Address: 192.168.4.255 (all host bits set to 1)
Last Available Host Address: 192.168.4.254 (subtract 1)

Question 36

CIDR stands for __________.

Answer 36

Classless Inter-Domain Routing

Question 37

What is CIDR?

Answer 37

A method for allocating IP addresses and for IP routing. Introduced in 1993 to replace the previous classful network addressing. Its goal was to slow the growth of routing tables on routers across the Internet, and to help slow the rapid exhaustion of IPv4 addresses.

[Probably don’t need to know this. Just know CIDR replaced classes, I think]

Question 38

What is CIDR block notation?

Answer 38

A compact representation of an IP address and its associated network mask. Specifies an IP address, a slash (‘/’) character, and a decimal number. The decimal number is the count of leading 1 bits in the network mask. The number can also be thought of as the width (in bits) of the network prefix.

[Easier than it sounds. See examples below]

Question 39

CIDR block notation is also known as _______ and _______.

Answer 39

prefix notation

slash notation

Question 40

Show how a C class subnet mask can be written in decimal, binary, and in CIDR notation.

Answer 40

255.255.255.0
11111111.11111111.11111111.00000000
/24 (24 bits) i.e. the number of ones

(which also means network values will be 24 bits long and host values 8 bits long)

Question 41

Show how a B class subnet mask can be written in decimal, binary, and in CIDR notation.

Answer 41

255.255.0.0
11111111.11111111.00000000.00000000
/16

Question 42

Convert subnet class 255.255.255.192 to binary and CIDR notation.

Answer 42

11111111.11111111.11111111.11000000
/26

[Obviously a little harder since you can’t rely on Class A, B, or C conversion. Instead, you have to remember how to convert decimal to binary.]

Question 43

Convert subnet class 255.224.0.0 to binary and CIDR notation.

Answer 43

11111111.11100000.00000000.00000000

/11

Question 44

Draw a chart to help convert subnet mask octets from binary to decimal, and vice versa. (Show all nine possible values for a octet)

Answer 44

Binary               Decimal
00000000       0
10000000      128
11000000       192
11100000        224
11110000         240
11111000          248
11111100           252
11111110            254
11111111             255

[This is basically just taking our other binary-decimal conversion chart and taking it a step further. You’re just adding 128, then 64, then 32, 16, 8, 4, 2, 1]

Question 45

Convert /26 to binary and decimal.

Answer 45

11111111. 11111111.11111111.11000000

255. 255.255.192

Question 46

Convert /20 to binary and decimal.

Answer 46

11111111. 11111111.11110000.00000000

255. 255.240.0

Question 47

IPv4 addresses are made up of ______ (number) of _______, separated by __________.

IPv6 addresses are made up of ______ (number) of _______, separated by __________.

Answer 47

4
octets (decimal values between 0 and 255)
periods

8
segments (hexadecimal values between 0000 and FFFF)
colons

Question 48

Each segment of an IPv4 address is ____ bits, and an entire IPv4 address is ______ bits.

Each segment of an IPv6 address is _____ bits, and an entire IPv6 address is _____ bits.

Answer 48

8
32 (8 bits x 4 segments)

16
128 (16 bits x 8 segments)

Question 49

How IPv6 addresses are assigned:

The _________ provides address blocks to _________, such as _______ in North America, which then assigns smaller subnet blocks to ________, which then probably assign a /48 subnet to the customer.

Answer 49

IANA (Internet Assigned Numbers Authority)
RIRs (Regional Internet Registries)
ARIN
ISPs

Question 50

Break the following IPv6 address into three component parts:

2600:DDDD:1111:0001:0000:0000:0000:0001

Answer 50

2600:DDDD:1111 - Global Routing Prefix provided by IANA/RIR/ISP (48 bits)

0001 - Locally assigned network ID / Subnet (16 bits)

0000:0000:0000:0001 - Host ID (64 bits)

[Unclear if this is always the case]

Question 51

Why do we subnet a network?

Answer 51

We can’t connect every device in the world to each other. Not enough bandwidth or resources. Only one device can talk to another at a time. Also allows for segmentation, and perhaps provide additional security (e.g. add firewalls)

[Not totally clear on this]

Question 52

VLSM stands for __________.

Answer 52

Variable Length Subnet Masks

Question 53

VLSM can be referred to as _________ addressing, a more efficient alternative to _________.

Answer 53

classless

classful subnetting

Question 54

Explain how to determine if an IP address with CIDR-block notation is classful or classless.

And then specify whether the following examples are classful or classless

10. 0.0.0/8
11. 0.1.0/24
12. 0.8.0/26

Answer 54

1) Look at first octet of the IP address, and see if it falls in a class range (e.g. Class A = 1-126, Class B = 128=191, Class C = 192-223) So in our example, we see Class A
2) Convert CIDR-block notation to subnet mask. So, in our example, we know that /8 = 11111111.00000000.00000000.00000000. Which equals 255.0.0.0
3) Check that the Class of the IP address matches the appropriate subnet mask for that class. In this case, a class A IP address should have subnet mask of 255.0.0.0.

10. 0.0.0/8 IS classful. Because the first bit (10) is Class A, and the subnet mask (255.0.0.0) is also Class A.
11. 0.1.0/24 is classless. Because the first bit (10) is class A, but the subnet mask (255.255.255.0) would be class C. Doesn’t match up.
12. 0.8.0/26 is also classless. We actually know this because classful will always either be /8, /16, or 24.

Question 55

Explain how to determine how many subnet bits are in an address.

Answer 55

Take the number in the CIDR-notation and then subtract the number of subnet mask bits you’d expect given an IP address’ class.

Question 56

How many network bits, subnet bits, and host bits are in the following address?

10.0.0.0/8

Answer 56

Network bits = 8
Subnet bits = 0
Host bits = 24

Explanation: If the address is 10.0.0.0/8, you’d expect it to be Class A, which means the subnet mask is 255.0.0.0. So that’s 8 bits in the subnet mask. 8 CIDR minus the 8 expected = 0 subnet bits. And you have 8 network bits + 24 host bits for a total of 32 bits. (Total should always be 32 for IPv4 address)

Question 57

How many network bits, subnet bits, and host bits are in the following address?

10.0.1.0/24

Answer 57

Network bits = 8
Subnet bits = 16
Host bits = 8

If the address is 10.0.1.0/24, you expect Class A. Which means 255.0.0.0 (8 bit) subnet mask. But look at the /24. 24 - 8 = 16 subnet bits. And of course you have the 8 network bits. Which leaves 8 host bits. (Subnet bits always borrow from the host bits).

Question 58

How many network bits, subnet bits, and host bits are in the following address?

10.0.8.0/26

Answer 58

Network bits = 8
Subnet bits = 18
Host bits = 6

You expect class A due to leading bits of IP (10). So you expect 255.0.0.0 (8 bit) subnet mask. 26 - 8 = 18 subnet bits. 32 total bits - 8 network bits - 18 subnet bits = 6 host bits remaining.

When you look at it this way, it becomes very clear:
11111111.11111111.11111111.11000000

Question 59

How do you calculate number of available subnets?

Answer 59

2^subnet bits

[i.e. 2 to the power of the number of subnet bits. Wondering if I should have a power of twos chart written out?]

Question 60

How do you calculate number of available hosts per subnet?

Answer 60

2^host bits - 2

Question 61

For the following address, calculate number of available subnets.

10.0.1.0/24

Answer 61

2^16 = about 65k available subnets

(i.e. 2^subnet bits)

[I guess I’ll either need to memorize powers of two, learn a trick, or write out a chart. He has a chart in his video. Actually, maybe not. This is where we can use Messer’s 7 second subnetting]

Question 62

For the following address, calculate number of available hosts per subnet.

10.0.1.0/24

Answer 62

2^8 - 2 = 254 available hosts per subnet

i.e. 2^host bits - 2

Question 63

For the following address, calculate number of available subnets.

192.168.11.0/26

Answer 63

2^2 = 4 available subnets

(i.e. 2^subnet bits)

Explanation: Based on 192, we know Class C, which is 255.255.255.0, or /24 expected. Which means we have 2 subnet bits here (26-24). (Which means 6 host bits, by the way.)

Question 64

For the following address, calculate number of available hosts per subnet.

192.168.11.0/26

Answer 64

2^6 - 2 = 62 available hosts per subnet

(i.e. 2^host bits - 2)

Explanation: Based on 192, we know Class C, which is 255.255.255.0, or /24 expected. Which means we have 2 subnet bits here (26-24). Which means 6 host bits.

Question 65

For the following address, calculate number of available subnets.

172.16.55.0/21

Answer 65

2^5 = 32 available subnets

(i.e. 2^subnet bits)

Explanation: 172 means class B, which means we expect 255.255.0.0 (16 bits). We have 21 - 16 = 5 subnet bits

Question 66

For the following address, calculate number of available hosts per subnet.

172.16.55.0/21

Answer 66

2^11 - 2 = 2046 available hosts per subnet

(i.e. 2^host bits - 2)

[You know, when you’re looking for hosts per subnet, you don’t even need to look at Class. You simply subtract the CIDR notation (21) from number of bits in IPv4 (32), which gives you 11. In other words, host bits is always going to equal 32 - CIDR]

Question 67

165.245.12.88/24

Using Messer’s two 7-second subnetting charts, identify the following for the above address:

• Network address
• Broadcast address
• First usable IP address
• Last usable IP address

Answer 67

Network address: 165.245.12.0

Broadcast address: 165.245.12.255

First Usable IP address: 165.246.12.1

Last Usable IP address: 165.245.12.254

[Probably best to print out the two charts to use them. Will need to practice drawing them. Not including the drawing process in these cards]

Question 68

165.245.12.88/26

Using Messer’s two 7-second subnetting charts, identify the following for the above address:

• Network address
• Broadcast address
• First usable IP address
• Last usable IP address

Answer 68

Network address: 165.245.12.64

Broadcast address: 165.245.12.127

First Usable IP address: 165.245.12.65

Last Usable IP address: 165.245.12.126

Question 69

165.245.12.88/20

Using Messer’s two 7-second subnetting charts, identify the following for the above address:

• Network address
• Broadcast address
• First usable IP address
• Last usable IP address

Answer 69

Network address: 165.245.0.0

Broadcast address: 165.245.15.255

First Usable IP address: 165.245.0.1

Last Usable IP address: 165.245.15.254

Question 70

18.172.200.77/11

Using Messer’s two 7-second subnetting charts, identify the following for the above address:

• Network address
• Broadcast address
• First usable IP address
• Last usable IP address

Answer 70

Network address: 18.160.0.0

Broadcast address: 18.191.255.255

First Usable IP address: 18.160.0.1

Last Usable IP address: 18.191.255.254

Question 71

Initially released in 1997, _______ provides automatic IP address configuration for almost any device

Answer 71

DHCP (Dynamic Host Configuration Protocol

Question 72

The precursor to DHCP was known as ______.

Answer 72

BOOTP

Question 73

BOOTP stands for _________.

Answer 73

Bootstrap Protocol

Question 74

What is BOOTP?

Answer 74

Precursor to DHCP, a networking protocol released in 1993 that automatically assigns IP address to network devices from a configuration server. It required some manual configuration, and didn’t know when an IP address lease was up and available again.

Question 75

Prior to _______ and _______, IPv4 address configuration was manual.

Answer 75

BOOTP

DHCP

Question 76

When DHCP assigns IP addresses, they’re dynamic. That is, they occasionally change. What are the two options if you do not want an IP address to change on a device (e.g. a server or printer)?

Answer 76

1) Disable DHCP on that device, and configure the IP address info manually
2) Configure an IP reservation on the DHCP server, associating a specific MAC address with an IP address (Better solution)

Question 77

APIPA stands for __________.

Answer 77

Automatic Private IP Addressing

Question 78

What is APIPA?

Answer 78

A feature that enables a computer to self-configure an IP address / subnet mask so it can communicate with local devices even when a DHCP server is unavailable.

Question 79

APIPA functions by assigning devices a ______, which cannot be _______, but does allows the device to _________.

Answer 79

link-local address
forwarded by a router
communicate will all devices on local IP subnet

Question 80

How can you tell if APIPA has assigned a device a link-local address?

Answer 80

If the device’s IPv4 address begins with 169.254

[An IPv6 link-local address begins with fe80]

Question 81

APIPA uses _______ to confirm that a link-local address is not already in use.

Answer 81

ARP

Question 82

In IPv6 / DHCPv6, all devices are automatically assigned a ________ that begins with _______.

Answer 82

link-local address

fe80

Question 83

DHCPv6 uses multicast over which two ports?

Answer 83

udp/546 (client) and udp/547 (server)

[Remember that DHCPv4 uses ports udp/67 and udp/68]

Question 84

What are the four main steps used by DHCPv6?

Answer 84

1) DHCPv6 Solicit message to multicast address looking for DHCP servers
2) DHCP server replies with a DHCPv6 advertise message w/ associated IP address
3) DHCP client will receive list of all different advertisements from all DHCP servers on that subnet, will choose one, and then send back DHCPv6 request message
4) DHCPv6 server sends reply message, and client can then configure itself with IP address assigned by DHCP server

Question 85

EUI-64 stands for ____________.

Answer 85

Extended Unique Identifier

Question 86

What is EUI-64?

Answer 86

A method for automatically configuring IPv6 host addresses. An IPv6 device can use the MAC address of its interface to generate a static (unchanging) unique 64-bit interface ID. In other words,, a host can automatically assign itself a unique 64-bit IPv6 interface identifier without the need for manual configuration or DHCP. (Remember that the whole IPv6 address is 128-bits, of course)

Question 87

What is EUI-48?

Answer 87

Another term for MAC address, which is a 48-bit identifier for devices. (e.g. 8c:2d:aa:4b:98:a7)

Question 88

How do you convert a EUI-48 into a EUI-64, and why is it necessary?

Answer 88

It’s necessary, because if you want to use a 48-bit MAC address as a 64-bit identifier, you need extra bits.

Conversion process:

• Split MAC address into two 24-bit halves (e.g. 8c:2d:aa:4b:98:a7 becomes 8c:2d:aa and 4b:98:a7)
• Place FFFE in middle to give us missing 16 bits (e.g. You now have 8c2d:aaff:ee4b:98a7)
• Invert or “flip” the 7th bit (You can do this by converting hexadecimal to binary, then back to hexadecimal. OR you can use Prof Messer’s handy conversion chart)

[NOTE: You’re not flipping the 7th digit / character of the EUI-64. You’re flipping the 7th BIT when it’s written in binary]

Question 89

The seventh bit of a EUI-64 is also known as the _______. When you invert it, you are changing the address from ______ to ________.

Answer 89

U/L bit (Universal / Local)
Globally unique/universal
Locally administered

Question 90

Why is the 7th bit inverted?

Answer 90

If the U/L bit isn’t flipped, you’re always going to have a 1 (global) at 7th position. Problem is, that 1 causes uglier addressing and prevents shorthand notation. From RFC 2373: “The alternative would have been for these to be of the form 0200:0:0:1, 0200:0:0:2, etc., instead of the much simpler ::1, ::2, etc.”

[When you’re inverting it, you’re changing the U/L bit from universal to local, but that really doesn’t matter in the context of an IPv6 address. Doesn’t explain WHY you’re inverting it]

[Btw, this isn’t really important to know]

Question 91

Explain how an IPv6 address is built with a modified EUI-64. (i.e. Modified with a flipped bit).

Answer 91

First half of IPv6 address is the 64-bit IPv6 subnet prefix. (We can easily find this by sending a Neighbor Discovery Protocol to routers on local subnet.
And they’ll respond with this)

Second half of IPv6 address is the modified EUI-64 address. (Which we created by combining our modified MAC address and the FFFE in middle)

Question 92

Draw Prof Messer’s chart for flipping the 7th bit of an EUI-64, and explain how to use it.

Answer 92

Count from 0 to F in hexadecimal. (Two columns, groups of four.)

0 1
2 3

4 5
6 7

8 9
A B

C D
E F

And then you’re flipping the SECOND digit / character of the EUI-64 using this chart. 0 becomes 2, 1 becomes 3, 8 becomes A, 9 becomes B, etc.

(e.g. MAC address 8c:2d:aa:4b:98:a7 becomes 8e2d:aaff:fe4b:98a7).

Question 93

18:b4:30:10:7b:61

Convert the above MAC address to EUI-64.

Answer 93

1ab4:30ff:fe10:7b61

Question 94

a0:21:b7:63:40:3f

Convert the above MAC address to EUI-64.

Answer 94

a221:b7ff:fe63:403f

Question 95

34:62:88:dc:85:2f

Convert the above MAC address to EUI-64.

Answer 95

3662:88ff:fedc:852f

Question 96

What are the two types of network diagrams?

Answer 96

logical and physical

Question 97

What is a logical diagram?

Answer 97

A logical network diagram illustrates the flow of information through a network and shows how devices communicate with each other. It typically includes elements like subnets, network objects and devices, routing protocols and domains, voice gateways, traffic flow and network segments. In logical network diagrams, there are pivots for small, medium and large networks, where network diagram templates can be helpful.

(Helpful with virtualized equipment that isn’t physical. Shows high-level views, like how a WAN is connected, or how an application flows. e.g. web server to middleware to database on backend. Useful for planning or collaborating w/ third party)

Question 98

What is a physical diagram?

Answer 98

Think of physical network mapping like a floor plan. It shows all of the physical aspects and arrangement of the network, including ports, cables, racks and servers, as well as any other hardware or devices that apply.

(Would show the physical cable connections from one interface to another. Might even show where devices might be installed in a particular rack. Then you could go to a data center, to a specific rack, and identify exactly the piece of equipment that’s listed in documentation)

Question 99

What is the main factor that determines the kind of diagram you’ll use?

Answer 99

Network topology

[Don’t quite understand how…]

Question 100

Topology refers to what?

Answer 100

the arrangement of physical or logical aspects of a network

Question 101

What are the four basic types of network topologies?

Answer 101

Bus
Ring
Star
Mesh

[Note: there are a wide range of derivations in topologies, but they generally all stem from these four basic formats]

Question 102

What is a bus topology?

Answer 102

(aka. line, linear, backbone or ethernet topology)

Connects each computer via a cable to a central “bus” with exactly two endpoints. A bus is a connection that all other devices connect to. Think of a coaxial cable running through a room, with each device tapped in

Question 103

What are the advantages and disadvantages of a bus topology?

Answer 103

Advantages:

Great for small networks
Easiest topology for connecting computers and devices in a linear fashion
Requires less cable than some other topologies

Disadvantages:

If the central “bus” breaks down, your network goes down, which can leave you without access to important files and information at critical times.
Troubleshooting can be difficult
Not ideal for large networks
The more devices connected, the slower the network may become

Question 104

What is a ring topology?

Answer 104

Devices connect via a circular path, so each networked device is linked by two others in a “ring.” So, when data packets transmit to one device, they have to travel through the ring until they’ve reached their destination. Most ring topologies are unidirectional, meaning that data can only move in one direction. But bidirectional (two-way data travel) networks are possible.

Question 105

What are the advantages and disadvantages of a ring topology?

Answer 105

Advantages:

When all data flows in one direction, the odds of having packet collision are eliminated
Fast data transfers between workstations
Adding workstations doesn’t impact network performance
Doesn’t require a network server to control network connectivity between workstations

Disadvantages:

All data passes through each workstation on the network, which can cause a slowdown
If one workstation shuts down, it can impact the entire network
The hardware needed to connect workstations to the network can be expensive

Question 106

What is a star topology?

Answer 106

Features a central hub or switch that acts as a server, with the peripheral devices acting as clients. All data passes through the hub or switch before going to the connected device. Used in most large and small networks.

Question 107

What are the advantages and disadvantages of a star topology?

Answer 107

Advantages:

Centralized network management
Easy to add computers to the network
Improved reliability because individual devices won’t impact the whole network

Disadvantages:

If the central hub or switch fails, the entire network goes down
Primary network device controls performance and the number of nodes the network can handle
Costs for cabling and switches or routers can be high

Question 108

What is a mesh topology?

Answer 108

Generally used for wireless networks, connects computers and network devices. In full mesh topology, all nodes are connected, while with a partial mesh topology, at least two nodes in the network are connected to multiple other nodes in that network.

Question 109

What are the advantages and disadvantages of a mesh topology?

Answer 109

Advantages:

Several devices can transmit data simultaneously so that the network can manage high levels of traffic
Remains stable even when one device fails
Adding devices won’t disrupt data transmissions between devices

Disadvantages:

The cost to implement mesh networks can be high when compared to other topologies
Topology development and maintenance can be challenging
High likelihood of redundant connections, which can reduce efficiencies and increase costs

Question 110

What is a hybrid topology, and what is its purpose?

Answer 110

Combines at least two topologies to form something new. Makes it possible to gain the strengths of the topologies while reducing the disadvantages. For instance, by combining a bus and mesh technology, you’ll get a tree topology. However, you can also combine star and ring topologies, star and bus topologies, and use other combinations to get the performance you need. The possibilities are virtually endless.

Question 111

What are the two types of wireless topology identified by 802.11, and the third that has become more common?

Answer 111

• Infrastructure: All devices communicate through an access point. This is the most common wireless communication mode.
• Ad Hoc: Devices communicate amongst themselves. No access point or pre-existing infrastructure. Relatively uncommon. Does not scale well with more than 8-10 devices. Also known as IBSS (Independent Basic Service Set)
• Mesh: Ad hoc individual devices find each other and work together to form a mesh “cloud.” Self form and self-heal. Often used by Internet of Things (IoT). (According to one site, APs do play a role, bridging client traffic between each other. So maybe not always ad hoc?)

[Not 100% clear that mesh is a third topology type, or if it’s simply a type of ad hoc]

Question 112

BIA stands for _________.

Answer 112

Burned in Address

Question 113

What is a BIA?

Answer 113

A MAC address (also referred to as an Ethernet hardware address, hardware address, and physical address)

[Saw different answers online, but this comes directly from David Bombal. So I’m gonna go with him on this.]

Question 114

LAN stands for __________.

Answer 114

Local Area Network

Question 115

What is a LAN?

Answer 115

A computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. One of the most common network types.

Question 116

What are two very common types of LANs?

Answer 116

Ethernet

802.11 wireless

Question 117

WLAN stands for __________.

Answer 117

Wireless LAN

[Careful: Do not confuse with WAN]

Question 118

What is a WLAN?

Answer 118

A wireless computer network that links two or more devices using wireless communication to form a local area network within a limited area such as a home, school, computer laboratory, campus, or office building. Coverage can be expanded with additional access points. Uses 802.11.

Question 119

MAN stands for __________.

Answer 119

Metropolitan Area Network

Question 120

What is a MAN?

Answer 120

A computer network that connects computers within a metropolitan area, which could be a single large city, multiple cities and towns, or any given large area with multiple buildings. A MAN is larger than a LAN, but smaller than a WAN.

Question 121

WAN stands for __________.

Answer 121

Wide Area Network

Question 122

What is a WAN?

Answer 122

A network that extends over a large geographic area (i.e. miles), often established with leased telecommunication circuits. Useful if you need to connect two locations outside a Metropolitan area. (e.g. within state, within country, or even panning globe between countries). Generally connects LANs across a distance (and generally much slower than a LAN).

Many different WAN technologies, such as point-to-point serial, MPLS, etc. [?] Terrestrial and non-terrestrial (satellite).

Question 123

CAN stands for __________.

Answer 123

Campus Area Network (or Corporate Area Network)

Question 124

What is a CAN?

Answer 124

A network of multiple buildings, but within a limited geographical area. (i.e. within walking distance). Uses LAN technologies. High speed ethernet over your own fiber. (No third-party provider, so no monthly cost)

Question 125

SAN stands for __________.

Answer 125

Storage Area Network

Question 126

What is a SAN?

Answer 126

A computer network which provides access to consolidated, block-level data storage (i.e. doesn’t need to re-write an entire file. Can re-write just a portion). SANs are primarily used to access data storage devices, such as disk arrays and tape libraries from servers so that the devices appear to the operating system as direct-attached storage. Not to be confused with NAS.

Question 127

NAS stands for __________.

Answer 127

Network Attached Storage

Question 128

What is NAS?

Answer 128

A file-level (as opposed to block-level storage) computer data storage server connected to a computer network. A single storage device that serves files over Ethernet and is relatively inexpensive and easy to set up. Appears to user as a mounted network drive (rather than direct-attached storage, like a SAN).

Question 129

PAN stands for __________.

Answer 129

Personal Area Network

Question 130

What is PAN?

Answer 130

A computer network for interconnecting electronic devices within an individual person’s workspace. A PAN provides data transmission among devices such as computers, smartphones, tablets and personal digital assistants. PANs can be used for communication among the personal devices themselves, or for connecting to a higher level network and the Internet where one master device takes up the role as gateway.

Noted: A PAN may be wireless or wired (e.g. USB)

Question 131

Name three common wireless PAN technologies.

Answer 131

Bluetooth, IR, and NFC

Question 132

Name a few common examples of PANs.

Answer 132

• Automobiles (integrated w/ phone for audio output)
• Mobile phones connected to wireless headsets
• Health-monitoring devices (e.g. workout telemetry)

Question 133

IoT stands for __________.

Answer 133

Internet of Things

Question 134

What is IoT?

Answer 134

The network of physical objects—a.k.a. “things”—that are embedded with sensors, software, and other technologies for the purpose of connecting and exchanging data with other devices and systems over the Internet.

Question 135

Name two very common examples of IoT.

Answer 135

Wearable technology (e.g. smart watches, health monitors, glasses)

Home Automation (e.g. video doorbells, smart thermostats, robotic vacuums, Internet-connected garage doors)

Question 136

Name some of the most common technologies / topologies / protocols used in IoT (x7).

Answer 136

802.11
Bluetooth
IR
RFID
NFC
Z-Wave
Ant / ANT+

Question 137

Z-Wave is often used for ________. It uses ________ networking (nodes can hop through other nodes on way to destination). Commonly communicates over __________ using _____ frequencies in the US, so no conflicts with ________.

Answer 137

home automation (e.g. controlling lights, locks, garage doors)
wireless mesh
ISM band (Industrial, scientific, and medical)
900 MHz
802.11

Question 138

ANT / ANT+ is often used for _________. It is an ultra ________ protocol that communicates over ______ using __________ frequencies. It is vulnerable to _____ attacks. ______ is optional and there is no method to ________.

Answer 138

Fitness devices, heart rate monitors, etc.
ultra-low-power protocol
ISM band (industrial, scientific, and medical)
2.4 GHz
Denial of service (Spectrum jamming is possible)
Encyrption
Maintain integrity

Question 139

Bluetooth is often used for ________, providing ______ over ________.

Answer 139

Connecting our mobile devices (Smartphones, tethering, headsets and headphones, health monitors, automobile and phone integration, smartwatches)

high speed communication
short distances

Question 140

NFC stands for ________.

Answer 140

Near field communication

Question 141

NFC is most commonly known for its use in ________. It is also used as a _______ and can be used for _________. It builds on the older technology _______, but uses ______ communication instead of ________

Answer 141

Payment systems / credit cards / online wallets (I think where you hold phone near credit card reader to pay)

Bootstrap for other wireless networks (can help with bluetooth pairing)

Access token or identity card (short range w/ encryption support)

two-way
one-way

Question 142

IR stands for _______.

Answer 142

Infrared

Question 143

IR is most commonly used for ________, but is also included in many ________. It was previously used for ________ and _______, but no longer.

Answer 143

Remote controls for entertainment centers
Smartphones, tablets, smart watches
File transfers
Printing

Question 144

RFID stands for ________.

Answer 144

Radio-frequency identification

Question 145

Name four common uses for RFID

Answer 145

• Access badges
• Inventory / assembly line tracking
• Pet / animal identification
• Anything that needs to be tracked

Question 146

Explain how RFID works.

Answer 146

Tags usually aren’t powered.
Power comes from RF energy transmitted to the tag, at which point ID is transmitted back.
There is bi-directional communication.

Question 147

802.11 is a _______ technology, managed by the _______ committee and tested for interoperability by _______.

Answer 147

wireless networking
IEEE LAN/MAN Standards Committee (IEEE 802)
Wi-Fi Alliance

Question 148

List the five 802.11 wireless networking standards in the order of their introduction (along with the years they were introduced).

Answer 148

802. 11a (1999)
803. 11b (1999)
804. 11g (2003)
805. 11n (2009)
806. 11ac (2014)

Question 149

802.11a operates in the ____ frequency range, with throughputs up to ________.

Answer 149

5 GHz (or other frequencies w/ special licensing)
54 Mbit/s

Question 150

802.11b operates in the ____ frequency range, with throughputs up to ________.

Answer 150

2.4 GHz
11 Mbit/s

[Be careful: It’s counter-intuitive, but the first standard was NOT the slowest. ]

Question 151

802.1a was significantly faster than 802.1b, but explain its major disadvantage.

Answer 151

Had a much smaller range (about 1/3 the distance). This is because the higher frequency 5 GHz was absorbed by objects, while 2.4 GHz bounced off objects.

[Unclear how this shortcoming of 5 GHz is overcome in 802.11ac, which uses 5 GHz due to its greater bandwidth]

Question 152

What was the other disadvantage of 802.1b compared to 802.1a, other than speed?

Answer 152

More frequency conflict (e.g. Baby monitors, cordless phones, microwave ovens, Bluetooth)

Question 153

802.11g operates in the ____ frequency range, with throughputs up to ________.

Answer 153

2.4 GHz
54 Mbit/s

[Messer says a little bit less throughput than 802.11a even though max is supposedly the same]

Question 154

Basically, 802.11g combined the frequency (and better range) of the _________ standard, with the higher speed of the ________ standard.

Answer 154

802. 11b

802. 11a

Question 155

802.11g was backwards compatible with ________, meaning __________.

Answer 155

802.11b

An 802.11 access point would work with 802.11 client

Question 156

802.11g suffered the same frequency conflict problems as __________.

Answer 156

802.11b

Question 157

802.11n operates in the ____ frequency range, with throughputs up to ________.

Answer 157

5 GHz and/or 2.4 GHz

600 Mbit/s

Question 158

802.11n achieves its faster speeds by using ______ channel widths (a lot more bandwidth), and four _______.

Answer 158

40MHz channel widths

4 antennas

Question 159

802.11n was the first wireless networking standard to use what?

Answer 159

MIMO (pronounced “my moe”)

Question 160

MIMO stands for ________.

Answer 160

multiple input, multiple output

Question 161

What is MIMO?

Answer 161

Wireless networking technology introduced in 802.11n that allows for up to 4 streams with its multiple transmit and receive antennas.

(If you see a wireless router with multiple antennas, you know it’s 802.11n or later)

Question 162

802.11ac operates in the ____ frequency range, with throughputs up to ________.

Answer 162

5 GHz exclusively*
7 Gbit/s theoretically (1.7 - 2.5 Gbp/s in reality)

*If you see a dual-band 802.11ac router offering 2.4 GHz, it’s actually using 802.11 for 2.4 GHz

Question 163

802.11ac achieves its faster speeds by using ______ channel widths (a lot more bandwidth), increased ______, denser _______, and eight _______.

Answer 163

80 MHz or 160 MHz

channel bonding (bonds channels together to support larger bandwidth)

denser signaling modulation (faster data transfer)

8 antennas

Question 164

MU-MIMO stands for _______.

Answer 164

Multi-user MIMO

Question 165

What is MU-MIMO?

Answer 165

Wireless networking technology introduced in 802.11ac that allows for up to 8 streams with its multiple transmit and receive antennas.

Unlike regular MIMO introduced in 802.11n, this allows multiple devices at a single time.

Question 166

The number of available streams in 802.11n and 802.11ac are depending upon what?

Answer 166

The number of antennas on access point and client

Antennas on the access point) x antennas on the client: number of streams

(e.g. 2x2:2, 4x4:4)

Question 167

What frequencies are currently used in 802.11 wireless technologies?

Answer 167

2.4 GHz, 5 GHz, or sometimes both

Question 168

Explain how channels work in 802.11 wireless technologies.

Answer 168

Channels are groups of frequencies, numbered by the IEEE. Frequencies are grouped into channels so we don’t have to remember the exact frequencies in a range, which makes it easier to reference when configuring a wireless access point.

Question 169

When you’re configuring multiple access points to communicate, what’s important to remember about channels?

Answer 169

To avoid conflicts, you want to choose channels that don’t overlap with each other

Question 170

When referring to 802.11 wireless standards, explain what bandwidth mean. And how the standards increase it.

Answer 170

The amount of frequency being used at any particular time. Can be increased by using more frequency ranges.

Question 171

Give channel bandwidths for the five 802.11 standards.

Answer 171

802. 11a - 20 MHz
803. 11b - 22 MHz
804. 11g - 20 MHz
805. 11n - 20 MHz or 40 MHz (using two contiguous 20 MHz bonded channels)
806. 11ac - 80 MHz or 160MHz (contiguous channels or non-contiguous bonded channels)

[Also: 802.11ac uses 40 MHz for 802.11n stations, at a minimum]

Question 172

What are some things to consider about power level controls (i.e. how much signal you’re sending out) on access points?

Answer 172

If you’re in a crowded area with a lot of wireless access points, you want to minimize how far the signal travels. So you want to set it as low as you can using router software.

This might require additional site surveys. You want to make sure you’re maintaining speeds across required distances.

Question 173

What are two big considerations when it comes to wireless receivers?

Answer 173

Antennas. You may have a choice. (e.g. high gain antenna)

Location, location, location.

Question 174

Explain the difference between omnidirectional and directional antennas.

Answer 174

Omnidirectional evenly distributes signal on all side. Good choice for most environments if you need coverage in all directions, but you need to place access point in central location. Has no ability to focus signal, so if access point can’t be placed centrally, you’ll need a different antenna.

Directional focuses signal in a particular direction. Sends and receives in a single direction. The benefit is you get increased distances (e.g. if you want to send signal across buildings)

Question 175

Wireless antenna performance is measured in _____. Power is doubled with every ________.

Answer 175

dB (decibels)
3dB of gain

(e.g. 4dB is not twice as powerful as 3dB. The increase is logarithmic instead of linear)

Question 176

List four survey tools you can use when setting up or evaluating a wireless network.

Answer 176

• You can walk around with mobile phone looking at
  - Signal Coverage
  - Potential interference
• Built-in OS tools
• Spectrum analyzer (for a precise view)
• 3rd party tools (well, this is vague)

Question 177

Give a very simple explanation of how cellular networks function.

Answer 177

Geographical areas are separated into “cells” that resemble a beehive honeycomb.

Antennas cover each cell with certain frequencies.

Mobile or “cell” phones connect to those antennas when located within their particular cell.

Question 178

What are the three main cellular network standards that have been used?

Answer 178

GSM, CDMA, LTE

Question 179

The two primary standards in the early days of cellular networks were _____ and ______. They worked on ____ networks.

Answer 179

GSM
CDMA
2G

Question 180

What’s the primary weakness of GSM and CDMA?

Answer 180

Poor data support. Originally designed for voice communication and used circuit-switching. Eventually received some minor upgrades for some packet-switching.

Question 181

GSM stands for _______.

Answer 181

Global System for Mobile Communications

Question 182

What is GSM?

Answer 182

• A cellular networking standard
• Originally an EU standard, but eventually had 90% of the market worldwide.
• Used by AT&T and T-Mobile in the US
• Required moving SIM card (Subscriber Identity Module) from phone to phone
• Originally used TDMA

Question 183

TDMA stands for ________.

Answer 183

Time Division Multiple Access

Question 184

What is TDMA?

Answer 184

A cellular technology originally used by GSM standard where everyone on a particular frequency gets a little slice of time.

Involved combining multiple streams into a single stream (with a multiplexer), and then breaking into separate streams again (with a demultiplexer).

Question 185

CDMA stands for ________.

Answer 185

Code Division Multiple Access

Question 186

What is CDMA?

Answer 186

A cellular standard that used identifiable codes rather than time for its multiplexing.

Everyone could communicate at the same time, with each call using a different code. Codes used to filter calls on the receiving side.

Commonly used by Verizon and Sprint, without much adoption elsewhere. Handsets controlled by network provider.

Question 187

LTE stands for ________.

Answer 187

Long Term Evolution

Question 188

What is LTE?

Answer 188

A 4G cellular standard that most providers today have adopted.

Converged standard (GSM and CDMA providers), which means we no longer have to worry about providers giving us a phone.

Based on GSM and EDGE (Enhanced Data Rates for GSM Evolution)

Question 189

LTE supports download rates of _______. LTE-A (LTE Advanced) supports download rates of _______.

Answer 189

150 Mbit/s

300 Mbit/s

Question 190

SaaS stands for ________.

Answer 190

Software as a Service

Question 191

What is SaaS?

Answer 191

Cloud service that provides on-demand software with no local installation. Applications and data are centrally managed with everything running on external servers. A complete turnkey application with no development required. (e.g. Google Mail)

Question 192

IaaS stands for ________.

Answer 192

Infrastructure as a Service

Question 193

What is IaaS?

Answer 193

Cloud service that involves outsourcing your equipment, while you continue to manage software, security, etc. (Cloud provider might handle OS.) Your data is out there, but more within your control. (e.g. Web server providers, AWS EC2, Digital Ocean, Linode, MS Azure, Google Compute Engine (GCE)

Question 194

IaaS is also known as _________.

Answer 194

HaaS (Hardware as a Service)

Question 195

PaaS stands for ________.

Answer 195

Platform as a Service

Question 196

What is PaaS?

Answer 196

Cloud service that manages everything but the development. No physical servers, software, maintenance team, data center, etc. You don’t have direct control of data, people, or infrastructure. Trained security professionals watch your stuff. Choose carefully, Messer says

[E.g. AWS Lightsail, AWS Elastic Beanstalk, Google App Engine, Heroku, OpenShift]

Question 197

What are the trade-offs between IaaS and PaaS?

Answer 197

PaaS streamlines / simplifies things, allowing you to focus on high-level advanced programming. Provides modular building blocks you can put together in sandbox. Can make things a bit cheaper up-front, as app development becomes more cost and time effective.

However, price climbs as application scales. And once you commit to a PaaS, you’re locked into environment and interface. Expensive to change. PaaS less flexible / resilient, offering less access to servers and storage.

[Think about my experience when trying to choose between AWS EC2 and Lightsail. Same issue. EC2 requires more work up-front and is a bit more expensive. But with Lightsail, couldn’t even choose what version of PHP to use]

Question 198

What is a cloud deployment model?

Answer 198

It’s the specific configuration of environmental parameters. Basically, who controls the cloud infrastructure and where it’s located.

Question 199

What are the four main cloud deployment models?

Answer 199

Public
Private
Community
Hybrid

[There’s also multiclouds and poly clouds, but not on the exam]

Question 200

Describe the public cloud deployment model, along with pros and cons.

Answer 200

This is what you typically think of. It’s available to the general public, with data created and stored on third-party servers. Third-party providers like AWS own the server infrastructure and pool the resources.

Pros:

• Cost savings. Eliminates need to buy your own hardware
• Less hassle. No need to maintain hardware
• Scale resources up or down as needed
• Improved reliability and uptime (In theory. There are still some big outages)

Cons:

• Security and privacy
• Lack of flexibility. May not satisfy very specific, complex requirements

Question 201

Describe the private cloud deployment model, along with pros and cons.

Answer 201

Same as public in terms of technical aspects, but the hardware is owned by the user company instead of a 3rd party. Also called internal or corporate model. Servers can be hosted off-site or on-premises.

Pros:

• Better security and privacy
• Greater customization options

Cons:
-COST. Considerable expense on hardware, software, and staff training. Really only available for huge companies

[A lot of public cloud providers also offer private cloud services. e.g. Amazon, IBM, Cisco, Dell, and Red Hat]

Question 202

Describe the community cloud deployment model, along with pros and cons.

Answer 202

Resembles private. Only difference is that instead of being owned by one company, it’s owned by several organizations with similar security, privacy, and performance needs.

Pros:
Cheaper than private

Cons:
Costlier than public
A little less secure than private/hybrid
A little less flexible than private/hybrid (Fixed capacity. And you have to consider needs of other orgs)
Not commonly used

Question 203

Describe the hybrid cloud deployment model, along with pros and cons.

Answer 203

Allows companies to mix and match the facets of public, private, and community that best suit their requirements.

e.g. Can locate mission-critical workloads on secure private cloud while deploying less sensitive ones to public cloud.

Pros:
Cheaper than private, but costlier than public
Facilitates data and application portability [how?]

Cons:
Only makes sense if company can split their data into sensitive v. non-sensitive.

Question 204

Discuss three different ways to connect to a cloud.

Answer 204

Existing Internet Connection
-Browser-based - (w/ SSL or TLS encryption)

VPN (Virtual Private Network)

- When entire site of people need secure access
- Encrypted tunnel for *all* traffic between you and the cloud
- Probably require some additional hardware on both ends (e.g. firewalls)

Direct connection

- When security is of utmost importance 
- Co-location, same shared data center
- high speed 10 Gigabit connection
- No external traffic (added security)

Question 205

CASB stands for ________.

Answer 205

Cloud access security broker (pronounced ‘caz-bee’)

Question 206

What is a CASB?

Answer 206

On-premises or cloud based software that sits between cloud service users and cloud applications, and monitors all activity and enforces security policies.

• Visibility (What apps are being used and by whom)
• Compliance (e.g. Are users complying with HIPAA for medical info and PCI for credit card info?)
• Threat prevention (prevent attacks and unauthorized access)
• Data security. Ensure all data transfer encrypted. Prevent transfer of PII (personally identifiable) info with DLP (data loss prevention)

Question 207

DNS stands for ________.

Answer 207

Domain Name System

Question 208

What is DNS?

Answer 208

Translates human-readable names into computer-readable IP addresses (e.g. So you only need to remember google.com instead of the IP)

A very distributed database, consisting of many DNS servers and 13 root server clusters. (We may need to talk to a number of servers before we can fully resolve an IP address.)

Question 209

TLD stands for ________.

Answer 209

top-level domain

Question 210

What is a TLD?

Answer 210

The last level of every FQDN

Question 211

What are the two types of TLD?

Answer 211

Generic top-level domains (gTLD) - e.g. com, org, net, edu, gov, mil, and hundreds of others

Country code top-level domains (ccTLD) - e.g. us, ca, uk (over 275)

Question 212

Describe the DNS hierarchy.

Answer 212

-Top-Level Domains (TLDs) at the top (.com, .net, .org, .edu, us, ca, uk)

Under .com, you might have another domain like .google

Under that, might be web server called www, or .mail for mail server

And you can have levels beneath that. Like east.live.google.com

Question 213

FQDN stands for ________.

Answer 213

Fully Qualified Domain Name

Question 214

What is FQDN, and what are its four parts?

Answer 214

The most complete domain name that identifies a host or server. Its format is: [hostname].[domain].[tld].

• Hostname: www, mail, ftp, store, support, etc
• Domain: apple, microsoft, ibm, facebook, etc
• Top Level Domain (TLD): .com, .net, .org, .co.uk, etc
• Trailing period: Indicates end of name, implying previous string is tld

Question 215

In the DNS process, what is a resolver?

Answer 215

Any device (e.g. a laptop) trying to find an IP address associated with domain name

Question 216

What are the four types of DNS servers?

Answer 216

Root, TLD, Authoritative, and Local

[There’s actually a fifth we don’t need to know. I believe a recursive resolver / DNS recursor acts as middleman between a client and a DNS server. It’s sort of like a local cache, except it’s maintained by the ISP]

Question 217

What is a root server?

Answer 217

One of 13 logical root name servers that maintain list of gTLD and ccTLD servers

[Note I said ‘logical.’ Does not mean there are only 13 physical servers]

Question 218

What is a TLD name server?

Answer 218

A fixed set of name servers that maintain a list of the authoritative (master/slave) name servers for every registered domain. Typically located at companies contracted to provide the service by ICANN or government institutions.

Question 219

What is an authoritative server?

Answer 219

A master/slave server for a particular domain that has been configured by an administrator with the hostname information for that domain. Information about these servers is added to the root servers when the domain is registered

[Typically hosted by domain registrar, but it can be a web host, as well. I’ve used Dreamhost, for example]

[Be careful, I’ve seen root and TLD servers also referred to as ‘authoritative’]

Question 220

What is a local name server?

Answer 220

(aka. caching/forwarding server) Caches DNS info for local clients once it has been retrieved from root server. The local server can speed up name queries for local network by serving up names found by prior queries, preventing unnecessary additional requests to root server

Might be within organization or external 3rd party. Often specified by ISP, but can be changed for improved speed and security

Question 221

Where would you go to find out your local DNS server?

Answer 221

cmd > ipconfig /all

Question 222

What’s the difference between internal, external, and 3rd party DNS?

Answer 222

Internal DNS

 - Managed on internal servers
 - Configured and maintained by local network team
 - Contains DNS info about internal devices
 - Helpful for security (not publicizing)
 - Common to run on Windows Server

External DNS

 - Managed by a third-party
 - Does not have internal device info
 - e.g. Google DNS, Quad9

Third-party DNS

- Middle-ground where third-party provides internal DNS services
- Managing DNS servers can be challenging, especially in large environments
- Features not available on a privately-hosted DNS server    - High-availability, low latency, and scaling options

Question 223

What is a Resource Record (RR), and what are some common types?

Answer 223

An entry in a DNS zone file. The basic building block of host-name and IP information that is used to resolve a DNS query. There are over 30 record types.

e.g. A, AAAA, CNAME, MX, NS, PTR, SRV, TXT

Question 224

What is an A record?

Answer 224

IPv4 address record. Returns a 32-bit IPv4 address, most commonly used to map hostnames to an IP address of the host

Question 225

What is an AAAA record?

Answer 225

IPv6 address record. Returns a 128-bit IPv6 address, most commonly used to map hostnames to an IP address of the host.

Question 226

What is a CNAME record?

Answer 226

Canonical name record. A type of resource record in the Domain Name System (DNS) that maps one domain name (an alias) to another (the canonical name). Helpful when running multiple services (like an FTP server and a web server, each running on different ports) from a single IP address.

e.g. You can point ftp.example.com and www.example.com to the DNS entry for example.com, which in turn has an A record which points to the IP address

NOTE: CNAME records must always point to another domain name, never directly to an IP address.

Question 227

What is an SRV record?

Answer 227

Service locator. Find a specific service. Used for newer protocols instead of creating protocol-specific records such as MX.

e.g. Where is the Windows Domain Controller?
Where is the instant messaging server?
Where is the VoIP controller?

[So basically, this was created so you don’t need a never-ending list of RR types]

Question 228

What is an MX record?

Answer 228

Mail exchange record. Determines the host name for the mail server. Allows 3rd parties to find your local mail servers. Not an IP address; it’s a name

Question 229

What is an NS record?

Answer 229

Name server record. Delegates a DNS zone to use the given authoritative name servers. In other words, points to the name of the server(s) for a particular domain

[e.g. ns1.dreamhost.com, ns2.dreamhost.com]

Question 230

What is a PTR record?

Answer 230

Pointer to a canonical name. Opposite of an A or AAAA. Instead of giving it a hostname and receiving an IP address, you give it an IP address and receive a hostname. The most common use is for implementing reverse DNS lookups.

(Unlike a CNAME, DNS processing stops and just the name is returned.)

Question 231

What is a TXT record?

Answer 231

Text record. Originally for human-readable text. But more often carries machine-readable data for things like SPF, DKIM, etc.

[Google uses to confirm that you’re really the owner of a specific domain, by having you place special code]

Question 232

What is SPF?

Answer 232

Sender Policy Framework. Prevents mail spoofing. Mail servers check that incoming mail really did come from your server by looking at TXT record

[Probably not on exam]

Question 233

What is DKIM?

Answer 233

Domain Keys Identified Mail. A method for signing outgoing mail, validated by mail server. You put your public key in the DKIM TXT record.

Question 234

Describe the four steps involved in process of DHCP leasing. (Remember, this applies to IPv4 only.)

Answer 234

• Step 1: Discover
  
  • DHCP Discover sent from one device to udp port 67 [when device first turned on]
    
    • Broadcast to all other devices on network
    • Because it’s a broadcast, it goes to router, then does not go any further
• Step 2: Offer
  
  • DHCP server offers IP address to requesting device (to udp port 68)
    
    • Again, it’s a broadcast that goes out to all devices on subnet
• Step 3: Request
  
  • There may be more than one DHCP Server on network and requesting device may have received more than one offer. Device will pick one of those offers, and then another broadcast address to UDP port 67
• Step 4: Acknowledgement
  
  • DHCP Acknowledgement sent from DHCP Server (udp/67) to broadcast address udp/68 confirming that requesting device has now leased that particular IP address and can configure it

[DORA]

Question 235

Describe some of the challenges a large organization faces in managing DHCP.

Answer 235

• Limited communication range
  
  • Uses IPv4 broadcast domain and stops at a router
• Multiple DHCP servers needed for redundancy (across different locations)
• Scalability is an issue. May not want or need to manage DHCP servers at every remote location

Question 236

What is a DHCP Relay / IP Helper?

Answer 236

Feature of many routers that sends DHCP requests across broadcast domains. That is, it takes a broadcast that would normally be stopped by router, and converts it to unicast. Helpful when we have multiple subnets.

Question 237

Explain how DHCP Relay / IP Helper works.

Answer 237

You configure router with a DHCP Relay IP address, and tell it the DHCP Server IP address.

*Step 1: Discover with DHCP Relay
- DHCP relay changes the source IP address to router [itself, I believe] and the
destination address to the DHCP Server IP address.
(Instead of broadcasting to everyone)

*Step 2: Offer with DHCP Relay
-DHCP Server then replies back to original router’s IP address
-When it reaches that address, router realizes it needs to be a broadcast. So it broadcasts to
entire subnet, and will be received by original device
[Needs to be a broadcast, I believe, because device has no IP for direct communication!]
[And then process continues in similar vein for next steps]

Question 238

IPAM stands for ________.

Answer 238

IP Address Management

Question 239

What is IPAM?

Answer 239

A means of planning, tracking, and managing the IP addresses used in a network. Very helpful in large networks, where managing DHCP and IP address pools can be challenging.

Features include:

• Control of DHCP reservations (e.g. identify problems and shortages)
• Reporting on IP address usage (e.g. time of day, user-to-IP mapping)
• Integrate DNS and DHCP so that each is aware of changes in the other
• Manage IPv4 and IPv6 from a single console

Question 240

What is a scope?

Answer 240

A single contiguous pool of IP addresses used by DHCP.

Each subnet has its own scope

    - 192.168.1.0/24
    - 192.168.2.0/24
    - 192.168.3.0/24

Question 241

When configuring DHCP, scope options include ______, where a specific IP address is supplied to a particular client, and ________, where a specific IP address is designated for NOT being given out.

Answer 241

reservation

exclusion

Question 242

What are the three types of DHCP address allocation?

Answer 242

Dynamic, Automatic, and Static

Question 243

What is Dynamic DHCP allocation?

Answer 243

This is when IP address are reclaimed by a DHCP server after a lease period ends, and the client may not get that same IP address again. (Will instead receive another randomly selected address from a pool.)

Question 244

What is Automatic DHCP allocation?

Answer 244

This is when the DHCP server keeps a list of past IP address assignments, so clients will get the same IP address after a lease ends. (IP addresses are permanently associated with device MAC addresses.)

Question 245

What is Static DHCP allocation?

Answer 245

This is when IP addresses are manually assigned by an administrator based on MAC address

(aka Static DHCP Assignment, Static DHCP, Address Reservation, IP Reservation)

Question 246

Describe the DHCP lease process.

Answer 246

When a network device requests an IP address and a DHCP server responds with one, it’s called a lease. Leases have a TTL (time to live), which can be administratively configured. At various points during the TTL (normally around the 50% and 85% points), the client attempts to renew the lease from the server. If the server cannot perform a renewal, the lease expires at 100 percent, and the client stops using the address.

If you reboot computer, there’s a reallocation process. DHCP will try to assign the same IP address if still available. Workstations can also manually release the IP address (e.g. moving to another subnet).