Messer - 1. Networking Concepts (Part 2 of 2) Flashcards
1
Q
Draw Prof. Messer’s binary-to-decimal conversion chart.
A
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]
2
Q
Using Prof. Messer’s binary-to-decimal conversion chart, convert 00000010 to decimal.
A
2
3
Q
Using Prof. Messer’s binary-to-decimal conversion chart, convert 10000000 to decimal.
A
128
4
Q
Using Prof. Messer’s binary-to-decimal conversion chart, convert 10000010 to decimal.
A
130
5
Q
Using Prof. Messer’s binary-to-decimal conversion chart, convert 11111111 to decimal.
A
255
6
Q
Using Prof. Messer’s binary-to-decimal conversion chart, convert 32 to binary.
A
00100000
7
Q
Using Prof. Messer’s binary-to-decimal conversion chart, convert 63 to binary.
A
00111111
8
Q
Using Prof. Messer’s binary-to-decimal conversion chart, convert 122 to binary.
A
01111010
9
Q
- 168.1.165 is a ________.
255. 255.255.0 is a _______.
A
IP address (IPv4) subnet mask
10
Q
What is a Default Gateway?
A
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.
11
Q
The Default Gateway must be an _____ on the ______.
A
IP address
local subnet
12
Q
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 _________.
A
IP address
Subnet Mask
Gateway IP address
13
Q
What is the purpose of a subnet mask?
A
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]
14
Q
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?
A
Network: 192.158.1.0
Host: 0.0.0.165
15
Q
All devices have a special IPv4 address called a _______, which provides an easy way to self-reference when trouble-shooting.
A
loopback address
16
Q
Depending on the operating system, loopback addresses can range from _______ to _______. However, some operating systems only recognize _________.
A
- 0.0.1
- 255.255.254
- 0.0.1
17
Q
How would you use a loopback address to ensure that a TCP/IP stack is working properly on a device.
A
In that device’s command line, type the following:
ping 127.0.0.1
18
Q
_______ addresses are set aside for future use or testing, and range from _______ to _________.
A
Reserved
- 0.0.1
- 255.255.254
[Not to be confused with private addresses]
19
Q
VIP (or VIPA) stands for _______.
A
Virtual IP Address
20
Q
What is a Virtual IP Address?
A
An IP address that doesn’t correspond to an actual physical network interface. Used for network address translation, fault-tolerance, mobility, etc.
21
Q
_____ subnetting has not been used since 1993 because ________. However, knowing subnet _____ is still helpful as a starting point for subnetting.
A
Classful
not an efficient way of IP addressing
classes
22
Q
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.
A
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
23
Q
What is the class and default subnet mask of the following IP address?
17.22.90.7
A
Class A
255.0.0.0
24
Q
What is the class and default subnet mask of the following IP address?
220.10.77.40
A
Class C
255.255.255.0
25
What is the class and default subnet mask of the following IP address?
165.245.0.1
Class B
| 255.255.0.0
26
What is the class and default subnet mask of the following IP address?
128.90.10.2
Class B
| 255.255.0.0
27
What is the class and default subnet mask of the following IP address?
191.77.24.250
Class B
| 255.255.0.0
28
What is the class and default subnet mask of the following IP address?
192.1.12.5
Class C
| 255.255.255.0
29
Given an IP address and subnet mask, how do you determine the network address?
This is equal to the first IP address of a subnet, which you can get by setting all host bits to 0 (0 decimal)
30
Given an IP address and subnet mask, how do you determine the first usable host address?
This is simply one number higher than the network address
31
Given an IP address and subnet mask, how do you determine the network broadcast address?
This is the last IP address of a subnet, which you get by setting all host bits to 1 (255 decimal)
32
Given an IP address and subnet mask, how do you determine the last usable host address?
This is simply one number lower than the broadcast address
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
```
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)
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
```
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)
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
```
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)
36
CIDR stands for __________.
Classless Inter-Domain Routing
37
What is CIDR?
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]
38
What is CIDR block notation?
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]
39
CIDR block notation is also known as _______ and _______.
prefix notation
| slash notation
40
Show how a C class subnet mask can be written in decimal, binary, and in CIDR notation.
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)
41
Show how a B class subnet mask can be written in decimal, binary, and in CIDR notation.
255.255.0.0
11111111.11111111.00000000.00000000
/16
42
Convert subnet class 255.255.255.192 to binary and CIDR notation.
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.]
43
Convert subnet class 255.224.0.0 to binary and CIDR notation.
11111111.11100000.00000000.00000000
| /11
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)
```
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]
45
Convert /26 to binary and decimal.
11111111. 11111111.11111111.11000000
| 255. 255.255.192
46
Convert /20 to binary and decimal.
11111111. 11111111.11110000.00000000
| 255. 255.240.0
47
IPv4 addresses are made up of ______ (number) of _______, separated by __________.
IPv6 addresses are made up of ______ (number) of _______, separated by __________.
4
octets (decimal values between 0 and 255)
periods
8
segments (hexadecimal values between 0000 and FFFF)
colons
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.
8
32 (8 bits x 4 segments)
16
128 (16 bits x 8 segments)
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.
IANA (Internet Assigned Numbers Authority)
RIRs (Regional Internet Registries)
ARIN
ISPs
50
Break the following IPv6 address into three component parts:
2600:DDDD:1111:0001:0000:0000:0000:0001
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]
51
Why do we subnet a network?
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]
52
VLSM stands for __________.
Variable Length Subnet Masks
53
VLSM can be referred to as _________ addressing, a more efficient alternative to _________.
classless
| classful subnetting
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
10. 0.1.0/24
10. 0.8.0/26
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.
10. 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.
10. 0.8.0/26 is also classless. We actually know this because classful will always either be /8, /16, or 24.
55
Explain how to determine how many subnet bits are in an address.
Take the number in the CIDR-notation and then subtract the number of subnet mask bits you'd expect given an IP address' class.
56
How many network bits, subnet bits, and host bits are in the following address?
10.0.0.0/8
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)
57
How many network bits, subnet bits, and host bits are in the following address?
10.0.1.0/24
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).
58
How many network bits, subnet bits, and host bits are in the following address?
10.0.8.0/26
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
59
How do you calculate number of available subnets?
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?]
60
How do you calculate number of available hosts per subnet?
2^host bits - 2
61
For the following address, calculate number of available subnets.
10.0.1.0/24
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]
62
For the following address, calculate number of available hosts per subnet.
10.0.1.0/24
2^8 - 2 = 254 available hosts per subnet
| i.e. 2^host bits - 2
63
For the following address, calculate number of available subnets.
192.168.11.0/26
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.)
64
For the following address, calculate number of available hosts per subnet.
192.168.11.0/26
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.
65
For the following address, calculate number of available subnets.
172.16.55.0/21
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
66
For the following address, calculate number of available hosts per subnet.
172.16.55.0/21
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]
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
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]
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
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
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
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
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
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
71
Initially released in 1997, _______ provides automatic IP address configuration for almost any device
DHCP (Dynamic Host Configuration Protocol
72
The precursor to DHCP was known as ______.
BOOTP
73
BOOTP stands for _________.
Bootstrap Protocol
74
What is BOOTP?
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.
75
Prior to _______ and _______, IPv4 address configuration was manual.
BOOTP
| DHCP
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)?
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)
77
APIPA stands for __________.
Automatic Private IP Addressing
78
What is APIPA?
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.
79
APIPA functions by assigning devices a ______, which cannot be _______, but does allows the device to _________.
link-local address
forwarded by a router
communicate will all devices on local IP subnet
80
How can you tell if APIPA has assigned a device a link-local address?
If the device's IPv4 address begins with 169.254
[An IPv6 link-local address begins with fe80]
81
APIPA uses _______ to confirm that a link-local address is not already in use.
ARP
82
In IPv6 / DHCPv6, all devices are automatically assigned a ________ that begins with _______.
link-local address
| fe80
83
DHCPv6 uses multicast over which two ports?
udp/546 (client) and udp/547 (server)
[Remember that DHCPv4 uses ports udp/67 and udp/68]
84
What are the four main steps used by DHCPv6?
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
85
EUI-64 stands for ____________.
Extended Unique Identifier
86
What is EUI-64?
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)
87
What is EUI-48?
Another term for MAC address, which is a 48-bit identifier for devices. (e.g. 8c:2d:aa:4b:98:a7)
88
How do you convert a EUI-48 into a EUI-64, and why is it necessary?
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]
89
The seventh bit of a EUI-64 is also known as the _______. When you invert it, you are changing the address from ______ to ________.
U/L bit (Universal / Local)
Globally unique/universal
Locally administered
90
Why is the 7th bit inverted?
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]
91
Explain how an IPv6 address is built with a modified EUI-64. (i.e. Modified with a flipped bit).
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)
92
Draw Prof Messer's chart for flipping the 7th bit of an EUI-64, and explain how to use it.
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).
93
18:b4:30:10:7b:61
Convert the above MAC address to EUI-64.
1ab4:30ff:fe10:7b61
94
a0:21:b7:63:40:3f
Convert the above MAC address to EUI-64.
a221:b7ff:fe63:403f
95
34:62:88:dc:85:2f
Convert the above MAC address to EUI-64.
3662:88ff:fedc:852f
96
What are the two types of network diagrams?
logical and physical
97
What is a logical diagram?
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)
98
What is a physical diagram?
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)
99
What is the main factor that determines the kind of diagram you'll use?
Network topology
[Don't quite understand how...]
100
Topology refers to what?
the arrangement of physical or logical aspects of a network
101
What are the four basic types of network topologies?
Bus
Ring
Star
Mesh
[Note: there are a wide range of derivations in topologies, but they generally all stem from these four basic formats]
102
What is a bus topology?
(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
103
What are the advantages and disadvantages of a bus topology?
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
104
What is a ring topology?
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.
105
What are the advantages and disadvantages of a ring topology?
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
106
What is a star topology?
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.
107
What are the advantages and disadvantages of a star topology?
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
108
What is a mesh topology?
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.
109
What are the advantages and disadvantages of a mesh topology?
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
110
What is a hybrid topology, and what is its purpose?
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.
111
What are the two types of wireless topology identified by 802.11, and the third that has become more common?
- 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]
112
BIA stands for _________.
Burned in Address
113
What is a BIA?
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.]
114
LAN stands for __________.
Local Area Network
115
What is a LAN?
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.
116
What are two very common types of LANs?
Ethernet
| 802.11 wireless
117
WLAN stands for __________.
Wireless LAN
[Careful: Do not confuse with WAN]
118
What is a WLAN?
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.
119
MAN stands for __________.
Metropolitan Area Network
120
What is a MAN?
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.
121
WAN stands for __________.
Wide Area Network
122
What is a WAN?
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).
123
CAN stands for __________.
Campus Area Network (or Corporate Area Network)
124
What is a CAN?
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)
125
SAN stands for __________.
Storage Area Network
126
What is a SAN?
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.
127
NAS stands for __________.
Network Attached Storage
128
What is NAS?
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).
129
PAN stands for __________.
Personal Area Network
130
What is PAN?
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)
131
Name three common wireless PAN technologies.
Bluetooth, IR, and NFC
132
Name a few common examples of PANs.
- Automobiles (integrated w/ phone for audio output)
- Mobile phones connected to wireless headsets
- Health-monitoring devices (e.g. workout telemetry)
133
IoT stands for __________.
Internet of Things
134
What is IoT?
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.
135
Name two very common examples of IoT.
Wearable technology (e.g. smart watches, health monitors, glasses)
Home Automation (e.g. video doorbells, smart thermostats, robotic vacuums, Internet-connected garage doors)
136
Name some of the most common technologies / topologies / protocols used in IoT (x7).
```
802.11
Bluetooth
IR
RFID
NFC
Z-Wave
Ant / ANT+
```
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 ________.
home automation (e.g. controlling lights, locks, garage doors)
wireless mesh
ISM band (Industrial, scientific, and medical)
900 MHz
802.11
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 ________.
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
139
Bluetooth is often used for ________, providing ______ over ________.
Connecting our mobile devices (Smartphones, tethering, headsets and headphones, health monitors, automobile and phone integration, smartwatches)
high speed communication
short distances
140
NFC stands for ________.
Near field communication
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 ________
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
142
IR stands for _______.
Infrared
143
IR is most commonly used for ________, but is also included in many ________. It was previously used for ________ and _______, but no longer.
Remote controls for entertainment centers
Smartphones, tablets, smart watches
File transfers
Printing
144
RFID stands for ________.
Radio-frequency identification
145
Name four common uses for RFID
- Access badges
- Inventory / assembly line tracking
- Pet / animal identification
- Anything that needs to be tracked
146
Explain how RFID works.
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.
147
802.11 is a _______ technology, managed by the _______ committee and tested for interoperability by _______.
wireless networking
IEEE LAN/MAN Standards Committee (IEEE 802)
Wi-Fi Alliance
148
List the five 802.11 wireless networking standards in the order of their introduction (along with the years they were introduced).
802. 11a (1999)
802. 11b (1999)
802. 11g (2003)
802. 11n (2009)
802. 11ac (2014)
149
802.11a operates in the ____ frequency range, with throughputs up to ________.
```
5 GHz (or other frequencies w/ special licensing)
54 Mbit/s
```
150
802.11b operates in the ____ frequency range, with throughputs up to ________.
2.4 GHz
11 Mbit/s
[Be careful: It's counter-intuitive, but the first standard was NOT the slowest. ]
151
802.1a was significantly faster than 802.1b, but explain its major disadvantage.
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]
152
What was the other disadvantage of 802.1b compared to 802.1a, other than speed?
More frequency conflict (e.g. Baby monitors, cordless phones, microwave ovens, Bluetooth)
153
802.11g operates in the ____ frequency range, with throughputs up to ________.
2.4 GHz
54 Mbit/s
[Messer says a little bit less throughput than 802.11a even though max is supposedly the same]
154
Basically, 802.11g combined the frequency (and better range) of the _________ standard, with the higher speed of the ________ standard.
802. 11b
| 802. 11a
155
802.11g was backwards compatible with ________, meaning __________.
802.11b
| An 802.11 access point would work with 802.11 client
156
802.11g suffered the same frequency conflict problems as __________.
802.11b
157
802.11n operates in the ____ frequency range, with throughputs up to ________.
5 GHz and/or 2.4 GHz
| 600 Mbit/s
158
802.11n achieves its faster speeds by using ______ channel widths (a lot more bandwidth), and four _______.
40MHz channel widths
| 4 antennas
159
802.11n was the first wireless networking standard to use what?
MIMO (pronounced "my moe")
160
MIMO stands for ________.
multiple input, multiple output
161
What is MIMO?
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)
162
802.11ac operates in the ____ frequency range, with throughputs up to ________.
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
163
802.11ac achieves its faster speeds by using ______ channel widths (a lot more bandwidth), increased ______, denser _______, and eight _______.
80 MHz or 160 MHz
channel bonding (bonds channels together to support larger bandwidth)
denser signaling modulation (faster data transfer)
8 antennas
164
MU-MIMO stands for _______.
Multi-user MIMO
165
What is MU-MIMO?
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.
166
The number of available streams in 802.11n and 802.11ac are depending upon what?
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)
167
What frequencies are currently used in 802.11 wireless technologies?
2.4 GHz, 5 GHz, or sometimes both
168
Explain how channels work in 802.11 wireless technologies.
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.
169
When you're configuring multiple access points to communicate, what's important to remember about channels?
To avoid conflicts, you want to choose channels that don't overlap with each other
170
When referring to 802.11 wireless standards, explain what bandwidth mean. And how the standards increase it.
The amount of frequency being used at any particular time. Can be increased by using more frequency ranges.
171
Give channel bandwidths for the five 802.11 standards.
802. 11a - 20 MHz
802. 11b - 22 MHz
802. 11g - 20 MHz
802. 11n - 20 MHz or 40 MHz (using two contiguous 20 MHz bonded channels)
802. 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]
172
What are some things to consider about power level controls (i.e. how much signal you're sending out) on access points?
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.
173
What are two big considerations when it comes to wireless receivers?
Antennas. You may have a choice. (e.g. high gain antenna)
Location, location, location.
174
Explain the difference between omnidirectional and directional antennas.
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)
175
Wireless antenna performance is measured in _____. Power is doubled with every ________.
dB (decibels)
3dB of gain
(e.g. 4dB is not twice as powerful as 3dB. The increase is logarithmic instead of linear)
176
List four survey tools you can use when setting up or evaluating a wireless network.
- 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)
177
Give a very simple explanation of how cellular networks function.
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.
178
What are the three main cellular network standards that have been used?
GSM, CDMA, LTE
179
The two primary standards in the early days of cellular networks were _____ and ______. They worked on ____ networks.
GSM
CDMA
2G
180
What's the primary weakness of GSM and CDMA?
Poor data support. Originally designed for voice communication and used circuit-switching. Eventually received some minor upgrades for some packet-switching.
181
GSM stands for _______.
Global System for Mobile Communications
182
What is GSM?
- 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
183
TDMA stands for ________.
Time Division Multiple Access
184
What is TDMA?
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).
185
CDMA stands for ________.
Code Division Multiple Access
186
What is CDMA?
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.
187
LTE stands for ________.
Long Term Evolution
188
What is LTE?
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)
189
LTE supports download rates of _______. LTE-A (LTE Advanced) supports download rates of _______.
150 Mbit/s
| 300 Mbit/s
190
SaaS stands for ________.
Software as a Service
191
What is SaaS?
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)
192
IaaS stands for ________.
Infrastructure as a Service
193
What is IaaS?
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)
194
IaaS is also known as _________.
HaaS (Hardware as a Service)
195
PaaS stands for ________.
Platform as a Service
196
What is PaaS?
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]
197
What are the trade-offs between IaaS and PaaS?
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]
198
What is a cloud deployment model?
It's the specific configuration of environmental parameters. Basically, who controls the cloud infrastructure and where it's located.
199
What are the four main cloud deployment models?
Public
Private
Community
Hybrid
[There's also multiclouds and poly clouds, but not on the exam]
200
Describe the public cloud deployment model, along with pros and cons.
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
201
Describe the private cloud deployment model, along with pros and cons.
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]
202
Describe the community cloud deployment model, along with pros and cons.
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
```
203
Describe the hybrid cloud deployment model, along with pros and cons.
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.
204
Discuss three different ways to connect to a cloud.
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)
205
CASB stands for ________.
Cloud access security broker (pronounced 'caz-bee')
206
What is a CASB?
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)
207
DNS stands for ________.
Domain Name System
208
What is DNS?
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.)
209
TLD stands for ________.
top-level domain
210
What is a TLD?
The last level of every FQDN
211
What are the two types of TLD?
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)
212
Describe the DNS hierarchy.
-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
213
FQDN stands for ________.
Fully Qualified Domain Name
214
What is FQDN, and what are its four parts?
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
215
In the DNS process, what is a resolver?
Any device (e.g. a laptop) trying to find an IP address associated with domain name
216
What are the four types of DNS servers?
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]
217
What is a root server?
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]
218
What is a TLD name server?
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.
219
What is an authoritative server?
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']
220
What is a local name server?
(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
221
Where would you go to find out your local DNS server?
cmd > ipconfig /all
222
What's the difference between internal, external, and 3rd party DNS?
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
223
What is a Resource Record (RR), and what are some common types?
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
224
What is an A record?
IPv4 address record. Returns a 32-bit IPv4 address, most commonly used to map hostnames to an IP address of the host
225
What is an AAAA record?
IPv6 address record. Returns a 128-bit IPv6 address, most commonly used to map hostnames to an IP address of the host.
226
What is a CNAME record?
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.
227
What is an SRV record?
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]
228
What is an MX record?
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
229
What is an NS record?
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]
230
What is a PTR record?
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.)
231
What is a TXT record?
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]
232
What is SPF?
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]
233
What is DKIM?
Domain Keys Identified Mail. A method for signing outgoing mail, validated by mail server. You put your public key in the DKIM TXT record.
234
Describe the four steps involved in process of DHCP leasing. (Remember, this applies to IPv4 only.)
* 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]
235
Describe some of the challenges a large organization faces in managing DHCP.
* 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
236
What is a DHCP Relay / IP Helper?
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.
237
Explain how DHCP Relay / IP Helper works.
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]
238
IPAM stands for ________.
IP Address Management
239
What is IPAM?
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
240
What is a scope?
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
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.
reservation
| exclusion
242
What are the three types of DHCP address allocation?
Dynamic, Automatic, and Static
243
What is Dynamic DHCP allocation?
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.)
244
What is Automatic DHCP allocation?
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.)
245
What is Static DHCP allocation?
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)
246
Describe the DHCP lease process.
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).
