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Network+ > Messer - 1. Networking Concepts (Part 1 of 2) > Flashcards

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

1
Q

To move data (e.g. HTTP) across a network, we need to package it up, encapsulate it within ___________ or ____________, which then needs to be encapsulated within ___________, which is then encapsulated within _____________.

A

TCP or UDP
IP
Ethernet

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2
Q

TCP and UDP are transported inside of, and encapsulated by ________.

A

IP Protocol

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3
Q

TCP and UDP operate at which layer of the OSI Model?

A

Layer 4 (Transport)

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4
Q

__________ allows us to use many different applications at the same time across a network, and is a nice feature of TCP and UDP.

A

Multiplexing

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5
Q

TCP stands for _____________.

A

Transmission Control Protocol

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6
Q

UDP stands for ________________.

A

User Datagram Protocol

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7
Q

How do TCP and UDP differ in terms of connections?

A

TCP is connection-oriented. A formal connection is made between separate devices on a network, data is transferred, and then the connection is formally terminated.

UDP is “connectionless.” There is no formal opening or closing of a connection. Data is sent whenever available, without acknowledgment from receiver.

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8
Q

How do TCP and UDP differ in terms of reliability?

A

TCP is “reliable.” It sends numbered data so if data is lost or out of order, it can recover from the error, re-order, and/or re-transmit the data.

UDP is “unreliable.” No error recovery. No re-ordering of data or retransmission.

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9
Q

In what way can UDP’s “connectionless unreliability” be an advantage?

A

No unnecessary overhead!

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10
Q

What is the purpose of a port number?

A

Port numbers are associated with different applications so data can be directed to the correct place within a device. (e.g. Port 80 - unencrypted web traffic)

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11
Q

What is a socket?

A

IP address + port number

[See notes - Feel like I’m missing stuff here]

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12
Q

What are the two types of port numbers?

A

Non-ephemeral / permanent (Commonly used by applications or services running on a server)

Ephemeral / temporary (Clients usually send randomly chosen port # when sending data)

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13
Q

TCP and UDP ports can be any between __________ and ___________.

A

0 and 65,535

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14
Q

Ports 0 to 1,023 are ______________.
Ports 1,024 to 49,151 are _________.
Ports 49,152 to 65,535 are __________.

A

System or well-known ports
User or registered ports
Dynamic, private, or ephemeral ports

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15
Q

What happens when TCP and UDP try to use the same port number simultaneously?

A

Nothing. There’s no conflict. e.g. One application can use TCP port 80 and another can use UDP port 80. (But wouldn’t normally see this.)

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16
Q

If we were to closely inspect an IP packet, what five things would we find?

A 
Source IP Address
Destination IP Address
TCP/UDP Source Port (randomly selected)
TCP/UDP Destination Port
Application Data (e.g HTTP, VoIP, email data)
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17
Q

ICMP stands for ____________.

A

Internet Control Message Protocol

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18
Q

What is the purpose of ICMP?

A

It’s like text messaging for network devices. Devices can request and reply to administrative requests (e.g. “Hey, are you there?”). Can let other devices know things aren’t going well (e.g. trouble communicating).

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19
Q

Like TCP/UCP, ICMP is carried by ___________. However, it is not used for ______________.

A

IP

data transfer

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20
Q

Telnet stands for __________________.

A

Telecommunication Network

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21
Q

Telnet port?

A

tcp/23

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22
Q

What is the purpose of Telnet?

A

Log in to devices remotely and access via text-based console. Way to communicate to and administer servers, routers, switches, and other devices.

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23
Q

Why isn’t Telnet the best choice for production systems?

A

It’s non-encrypted (e.g. user name and password in the clear)

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24
Q

SSH stands for _________________.

A

Secure Shell

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25
Q

SSH port?

A

tcp/22

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26
Q

What is the purpose of SSH?

A

Same as Telnet, but encrypted.

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27
Q

DNS stands for _________________.

A

Domain Name System

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28
Q

DNS port?

A

udp/53

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29
Q

SMTP stands for _________________.

A

Simple Mail Transfer Protocol

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30
Q

What is the purpose of DNS?

A

Converts IP addresses to more human-friendly domain names (e.g. 162.159.246.164 = www.professormesser.com)

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31
Q

SMTP port?

A

tcp/25

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32
Q

What is the purpose of SMTP?

A

Sending email (not receiving!)

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33
Q

FTP stands for _________________.

A

File Transfer Protocol

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34
Q

FTP Port?

A

tcp/20 (active mode data - actual data transfer)

tcp/21 (control - various commands)

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35
Q

What is the purpose of FTP?

A

Transferring files between systems

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36
Q

SFTP stands for _________________.

A

Secure File Transfer Protocol

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37
Q

SFTP port?

A

tcp/22

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38
Q

SFTP uses __________ as its underlying protocol, and therefore uses the same port number.

A

SSH

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39
Q

SFTP stands for _________________.

A

Trivial File Transfer Protocol

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40
Q

TFTP port?

A

udp/69 [think promiscuous]

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41
Q

What are the two main difference between TFTP and FTP / SFTP?

A

1) TFTP only reads and writes files. Lacks all other functionality (e.g. directory listings, resuming interrupted file transfers, etc.)
2) No username / password for authentication

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42
Q

DHCP stands for _________________.

A

Dynamic Host Configuration Protocol

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43
Q

DHCP port?

A

udp/67
udp/68

[Note: I believe this is for DHCPv4 only. I think DHCPv6 uses udp/546 (client) and udp/547 (server)]

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44
Q

DHCP assigns a ___________ to a device when that device ___________.

A

IP Address

First starts up

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45
Q

What is the purpose of DHCP?

A

Automatically configure IP address, subnet mask, DNS settings, etc.

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46
Q

DHCP requires a _____________, which in a small organization or home is often integrated into a ________________.

A

DHCP server

SOHO router

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47
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.)

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48
Q

DHCP assigns __________ to devices in real-time from a _____________ as part of a ____________, which must be renewed at set intervals.

A

IP addresses
pool
lease

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49
Q

Every device has a unique identifier known as a ____________, which DHCP servers use for assigning _____________.

A

MAC Address

IP Addresses

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50
Q

HTTP stands for _________________.

A

Hypertext Transfer Protocol

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51
Q

HTTP port?

A

tcp/80

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52
Q

What is the purpose of HTTP?

A

Web server communication

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53
Q

HTTPS stands for _________________.

A

Hypertext Transfer Protocol Secure

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54
Q

HTTPS port?

A

tcp/443

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55
Q

SNMP stands for _________________.

A

Simple Network Management Protocol

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56
Q

SNMP port?

A

udp/161

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57
Q

What is the purpose of SNMP?

A

Allows admins to monitor and configure network devices remotely. (e.g. servers, switches, routers, printers, etc.) You can gather a ton of information, like bandwidth being used, errors, device temps, even how much printer paper / toner is left.

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58
Q

Name two characteristics of SNMP v1

A

Structured tables

Unencrypted

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59
Q

Name three characteristics of SNMP v2

A 
Bulk transfers (easily request and receive a lot of info)
Data type enhancements
Still unencrypted
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60
Q

Name three characteristics of SNMP v3

A

Message integrity
Authentication
Encryption

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61
Q

RDP stands for _________________.

A

Remote Desktop Protocol

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62
Q

RDP port?

A

tcp/3389

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63
Q

What is the purpose of RDP?

A

Share a desktop from a remote location (e.g. allow help desk technician, remote administrator, scammer to see the screen of a remote computer)

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64
Q

The Windows application that uses RDP is called ______________.

A

Remote Desktop Connection

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65
Q

NTP stands for _________________.

A

Network Time Protocol

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66
Q

NTP port?

A

udp/123

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67
Q

What is the purpose of NTP?

A

To synchronize clock across network devices

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68
Q

Why is clock synchronization critical?

A

Log files, authentication, outage details

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69
Q

SIP stands for _________________.

A

Session Initiation Protocol

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70
Q

SIP port?

A

tcp/5060

tcp/5061

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71
Q

What is the purpose of SIP?

A

Voice over IP (VoIP). Setting up and managing sessions. Calling, ringing, hanging up.

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72
Q

Beyond voice communication, SIP is also used for ____________, ________________, and ______________________.

A

Video conferencing
Instant messaging
File transfers

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73
Q

Like SIP, another popular VoIP protocol is ___________________.

A

H.323

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74
Q

SMB stands for _________________.

A

Server Message Block

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75
Q

SMB port?

A

tcp/445

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76
Q

What is the purpose of SMB?

A

Protocol used by Microsoft Windows for sharing files, printers, etc.

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77
Q

SMB is also called _______________, which stands for ___________________.

A

CIFS (Common Internet File System)

[Technically, CIFS was a particular implementation of SMB that’s now obsolete. But people often use terms interchangeably.]

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78
Q

When SMB runs over tcp/445, it is a direct communication that does not rely on ____________ transport (like it did in the past).

A

NetBIOS

[Hope I have this one right. Very confusing info out there]

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79
Q

POP3 stands for _________________.

A

Post Office Protocol version 3

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80
Q

POP3 port?

A

tcp/110

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81
Q

What is the purpose of POP3?

A

Basic email receiving functionality. (Not sending, like SMTP!)

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82
Q

IMAP stands for _________________.

A

Internet Message Access Protocol

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83
Q

IMAP port?

A

tcp/143

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84
Q

What is the purpose of IMAP?

A

More advanced email receiving functionality. (Not sending, like SMTP!)

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85
Q

What is the current version of IMAP?

A

v. 4

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86
Q

What’s the primary difference between POP3 and IMAP?

A

POP3 retrieves messages from an email server (deleting them from server in the process).

IMAP does not remove messages, and allows for synchronization of inbox among multiple clients.

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87
Q

LDAP stands for _________________.

A

Lightweight Directory Access Protocol

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88
Q

LDAP port?

A

tcp/389

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89
Q

What is the purpose of LDAP?

A

Authentication protocol for directory services. Used as database to manage user and group privileges, allowing access to network devices such as printers, etc.

[This is a really tricky one. Not sure I got that entirely right.]

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90
Q

LDAPS stands for _________________.

A

Lightweight Directory Access Protocol Secure

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91
Q

LDAPS port?

A

tcp/636

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92
Q

LDAPS is a ___________ implementation of LDAP over _________.

A

non-standard

SSL

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93
Q

What is the purpose of H.323?

A

Manages Voice over IP (VoIP) sessions (e.g. call, ring, hang up). (See also SIP)

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94
Q

What does OSI stand for?

A

Open Systems Interconnection

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95
Q

The OSI model describes what?

A

The seven layers computer systems use to communicate over a network

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96
Q

Mnemonic for remembering OSI Model?

A

A Priest Saw Two Nuns Doing Pushups
All People Seem to Need Data Processing

Reverse: Please Do Not Throw Sausage Pizza Away

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97
Q

What is Layer 7 of the OSI model?

A

Application

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98
Q

What is Layer 6 of the OSI model?

A

Presentation

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99
Q

What is Layer 5 of the OSI model?

A

Session

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100
Q

What is Layer 4 of the OSI model?

A

Transport

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101
Q

What is Layer 3 of the OSI model?

A

Network

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102
Q

What is Layer 2 of the OSI model?

A

Data Link

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103
Q

What is Layer 1 of the OSI model?

A

Physical

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104
Q

The highest layer of the OSI Model is ______________, and the lowest is ______________.

A

Application

Physical

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105
Q

Layer 1 (Physical) involves what?

A

The physics of a network. The signaling, cabling, fiber optics, connectors, tools like punch-downs. Not about protocols. A physical layer problem would be something like a bad cable.

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106
Q

Layer 2 (Data Link) involves what?

A

Device-to-device data transfer within a network. Defines protocols for that communication, like DLC, LLC, PPP. Switching, bridging, or having two devices communicate using MAC addresses and Ethernet Frames.

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107
Q

Layer 3 (Network) involves what?

A

Communication between networks. This is the “routing” layer. Routers using IP addresses, fragmenting frames / data to traverse different networks

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108
Q

Layer 4 (Transport) involves what?

A

The functional and procedural means of transferring packets. This is the “post office” layer. It’s all about TCP and UDP, the most common protocols for transferring data across a network. TCP and UDP are almost synonymous with Transport Layer

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109
Q

Layer 5 (Session) involves what?

A

Connections between computers. It establishes, manages, and terminates connections between local and remote application. Establishes procedures for checkpointing, suspending, restarting, and terminating a session. In modern TCP/IP system, session layer is non-existent and simply part of the TCP protocol.

[Borrowed from Wikipedia for this. Prof. Messer was pretty unclear]

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110
Q

Layer 6 (Presentation) involves what?

A

Transforming data into a form an application accepts, or formatting application data to be sent across a network. May involve character encoding, encryption / decryption (SSL / TLS), or compression. Sometimes called “Syntax Layer.” Often combined with Layer 7 (Application).

[Odd that Presentation is not the layer involving user interaction.]

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111
Q

Layer 7 (Application) involves what?

A

Users interacting directly with software. It’s the layer we see when using a browser window, transferring a file, reading email. It’s all about “your eyes.”

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112
Q

Switches operate at what layer of the OSI model?

A

Layer 2 (Data Link)

[Intra-network]

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113
Q

Hubs operate at what layer of the OSI model?

A

Layer 1 (Physical)

[No protocols. Just raw data transfer]

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114
Q

Routers operate at what layer of the OSI model?

A

Layer 3 (Network)

[Between networks]

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115
Q

SOHO stands for ____________.

A

Small Office / Home Office

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116
Q

What is a SOHO Lan?

A

A small local area network (LAN) that typically consists of fewer than 10 computers.

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117
Q

What are an Ethernet Frame’s THREE most basic parts?

A

Header
Encapsulated Data
Trailer

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118
Q

What are an Ethernet Frame’s full EIGHT parts?

A

Header (Preamble, SFD, Destination MAC, Source MAC, and Type)
Encapsulated data (Data and Pad)
Trailer (FCS)

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119
Q

SFD stands for ____________.

A

Start Frame Delimiter

Designates end of an Ethernet Frame’s preamble

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120
Q

FCS stands for ____________.

A

Frame Check Sequence

CRC checksum of Ethernet Frame for error-checking

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121
Q

An Ethernet Frame is found at what layer of the OSI Model?

A

Layer 2 (Data Link)

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122
Q

An Ethernet Frame’s payload contains data from what layer of the OSI Model?

A 
Layer 3 (Network) and higher
(e.g. IP info, TCP data, browsing info)
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123
Q

PDU stands for ____________.

A

Protocol Data Unit

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124
Q

What is a PDU?

A

A specific block of information transferred over a network

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125
Q

A PDU is found at what layer of the OSI Model?

A

All layers

But it’s called different things at each layer

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126
Q

What is the PDU of OSI Layer 1 (Physical)?

A

Raw bits (1s or 0s) transmitted physically via the hardware

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127
Q

What is the PDU of OSI Layer 2 (Data Link)?

A

A frame (or series of bits)

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128
Q

What is the PDU of OSI Layer 3 (Network)?

A

A packet that contains the source and destination address

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129
Q

What is the PDU of OSI Layer 4 (Transport)?

A

A segment that includes a TCP header and data

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130
Q

What is the PDU of OSI Layer 5 (Session)?

A

The data passed to the network connection

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131
Q

What is the PDU of OSI Layer 6 (Presentation)?

A

The data formatted for presentation

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132
Q

What is the PDU of OSI Layer 7 (Application)?

A

The data received or transmitted by a software application

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133
Q

MAC Address stands for ____________.

A

Media Access Control Address

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134
Q

What is a MAC Address?

A

The unique “physical” address of a network device (also known as EUI-48)

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135
Q

A MAC Address is ________ bits / ________ bytes in length, and is displayed in ____________ format.

A

48
6
hexadecimal

(e.g. 8c:2d:aa:4b:98:a7)

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136
Q

A MAC address can be separated into what two halves?

A

Manufacturer - Organizationally Unique Identifier (OUI)

Serial Number - Network Interface Controller-Specific

137
Q

A hub is _______-duplex, and a switch is (usually) ________-duplex.

A

Half

Full

138
Q

What are the three main differences between a half-duplex and full-duplex Ethernet network?

A

Half-duplex:
Cannot send and receive data simultaneously
All traffic sent to all devices
Collisions possible

Full duplex:
Can send and receive data simultaneously
Traffic intelligently directed to appropriate device
No collisions

139
Q

CSMA/CD stands for ____________.

A

Carrier Sense Multiple Access with Collision Detection

140
Q

What is CSMA/CD?

A

An early ethernet protocol that controlled communication in half-duplex networks

141
Q

What does CS (Carrier Sense) mean in CSMA/CD?

A

Every node on network must listen for a period of no activity before trying to send a message

142
Q

What does MA (Multiple Access) mean in CSMA/CD?

A

Once a period of no activity occurs, every network node has equal opportunity to transmit a message

143
Q

What does CD (Collision Detect) mean in CSMA/CD?

A

If two nodes on network start transmitting at the same time, the nodes will detect collision and take appropriate action

144
Q

What are the three basic steps of CSMA/CD operation?

A

1) Listen for an opening (don’t transmit if network busy)
2) Once network is clear, attempt to send data
3) Handle collisions (Transmit jam signal so all devices know. Wait exponential back-off time and restart process)

145
Q

How did CSMA/CD improve original CSMA performance?

A

By terminating transmission as soon as collision detected, thus shortening time required before a retry could be attempted.

146
Q

Why do modern Ethernet networks no longer need CSMA/CD?

A

Because in modern Ethernet networks, built with switches and full-duplex connections, each Ethernet segment, or collision domain, is now isolated.

147
Q

Unlike a _________, which sends traffic to all interfaces / devices, a _____________ intelligently determines where traffic needs to go and sends to only that interface / device.

A

Hub

Switch

148
Q

CSMA/CA stands for ____________.

A

Carrier Sense Multiple Access with Collision Avoidance

149
Q

What is CSMA/CA and where is it used?

A

A newer ethernet protocol that controls communication in wireless networks (which are still half-duplex)

150
Q

Why doesn’t CSMA/CD work for wireless networks?

A

Wireless networks suffer from the “hidden node problem” or “hidden terminal problem.” Because nodes on a wireless network may not be in range of each other, they can not communicate directly, which makes collisions impossible to detect.

151
Q

What are the three basic steps of CSMA/CA operation?

A

1) Listen for an opening (don’t transmit if network busy)
2) Once network is clear, wait random time and then attempt to send data
3) Wait for acknowledgement (ACK) from recipient. If not received, wait exponential back-off time and restart process

[So two main differences between CA and CD is random wait time prior to sending data, and the ACK handshake in lieu of collision detection]

152
Q

RTS/CTS stands for ____________.

A

Ready to Send / Clear to Send

153
Q

What is RTS/CTS?

A

An optional protocol used by CSMA/CA to address “hidden node problem” and reduce probability of collisions.

154
Q

How does RTS/CTS work?

A

A wireless device asks permission to transmit from access point, which then grants permission. (i.e. Access point acts as traffic controller)

155
Q

What is the downside of RTS/CTS?

A

Introduces latency by adding another step in the CSMA/CA process. (Prior to the ACK handshake.)

156
Q

In what situation would it better to have RTS/CTS disabled?

A

When a network is small and doesn’t have any terminals / nodes that are out of range of each other. (i.e. isn’t susceptible to the “hidden node” problem)

157
Q

What is a collision?

A

When two nodes attempt to transmit data simultaneously, causing data loss. [Should move this card up higher]

158
Q

_______ is the network device responsible for forwarding or dropping frames.

A

A switch

159
Q

When does a switch drop frames?

A

When frames are corrupted

160
Q

A switch constantly updates its internal list of __________ based on _______________.

A

MAC addresses [and associated interfaces, I believe]

source MAC address of incoming traffic

161
Q

What are some alternate names for a switch’s Mac Address table?

A

CAM table, MAC forward table, MAC filter table, switching table, bridging table

162
Q

A switch maintains a _____-free environment, and uses _______ Protocol to do so.

A

loop

Spanning Tree Protocol (STP)

163
Q

What would F0/1, F0/2, F0/3 indicate on a switch?

A

These are Fast Ethernet Interfaces. The first number is card number and second is interface number. (e.g. F0/2 would mean Slot 0 / Interface 2)

164
Q

What does it mean if an Ethernet’s interface begins with G instead of F? (e.g. G0/1 v. F0/1)

A

This is a Gigabit Interface.

165
Q

What is the speed difference between Fast Ethernet and Gigabit Ethernet?

A

Fast Ethernet has max speed of 100 Mbps

Gigabit Ethernet has max speed of 1,000 Mbps (10x faster)

166
Q

What happens when a switch has a frame to transmit, but doesn’t have the destination MAC address in its table?

A

The switch performs a unicast flood, which is when a switch receives a unicast frame and treats it as a broadcast frame, flooding the frame to everyone. When intended unknown device receives frame, it replies to sender and switch can then note the device’s interface location in MAC address table.

(Note 1: this is how hubs used to work.)
(Note 2: This is not the same as MAC flooding, a type of network attack)

167
Q

ARP stands for ____________.

A

Address Resolution Protocol

168
Q

What is ARP?

A

A method for workstations (note: not switches) to discover MAC addresses of devices across a network in order to communicate with them. Does this by sending ARP Broadcast, asking for MAC address of a particular IP address on the network.

169
Q

What should you type at command line to view workstation’s local ARP table?

A

-arp -a

170
Q

What is a collision domain?

A

A segment of a network where packet collisions can occur

171
Q

Each port on a ______ is in the same collision domain. But each port on a _____, ______, or ______ is in a separate collision domain, which limits impact of collisions.

A

hub

bridge, switch, or router

172
Q

Today, we’ve effectively removed collision domains by adding _______ with _______ communication.

A

switches

full-duplex

173
Q

All ports on a hub or a switch are in the same ______, and all ports on a router are in a different __________.

A

broadcast domain

174
Q

What is a broadcast? Give three examples.

A

When a device sends info and everyone on a local IPv4 network receives it (within the limited scope of a broadcast domain)

ARP requests (seeking MAC address based on ipv4)
Operating system notifications
some dynamic routing protocols

175
Q

What is a potential problem with broadcasts, and how can it be resolved?

A

If a network has too many devices, broadcasts can slow things down. One way to limit broadcasts is to separate the network with a router in the middle.

[My question is: If broadcasts can be stopped without an issue, why were they necessary in the first place?)

176
Q

What is a unicast?

A

When one device sends info to another device (one-to-one relationship). Common in web browsing, file transfers, etc.

Note: There are two devices in a unicast

177
Q

What is the major weakness of unicasts?

A

Doesn’t always scale optimally (e.g. for real-time streaming live media event)

178
Q

Instead of using broadcasts, IPv6 networks use _______.

A

multicasts

179
Q

What is the difference between a broadcast and multicast?

A

Broadcast is one-to-all. Multicast is one-to-many. Instead of delivering info to all devices, only sends to interested / subscribed systems.

180
Q

What is the major weakness of multicasts

A

Difficult to scale across large networks because all devices need to know how to deal with it. (So both broadcasts and multicasts have scaling issues.)

181
Q

A ________ is the building block of network communication, and is transmitted by different protocols depending on the particular OSI layer.

A

Protocol Data Unit (PDU)

182
Q

MTU stands for ____________.

A

Maximum Transmission Unit

183
Q

What is a Maximum Transmission Unit (MTU)?

A

The size of the largest Protocol Data Unit (PDU) that can be communicated in a single network layer transaction.

Technically, refers to the size of an IP packet on the network layer. But people sometimes refer to Ethernet maximum frame size as MTU.

184
Q

A Maximum Transmission Unit (MTU) is measured in what?

A

Bytes (i.e. an octet of 8 bits)

185
Q

The _____ protocol uses Maximum Transmission Unit (MTU) to determine the maximum size of each packet.

A

Transmission Control Protocol (TCP)

186
Q

What is the upside and downside of a larger Maximum Transmission Unit (MTU)?

A

The upside is greater efficiency (more data / less overhead). The downside is larger packets are slower and cause delays.

187
Q

What happens when you try to transmit a Protocol Data Unit (PDU) that exceeds the Maximum Transmission Unit (MTU)?

A

The data is fragmented (i.e. broken into smaller pieces)

[From what I understand, this can occur at Data Link layer as well as Network layer]

188
Q

What are the downsides of fragmentation?

A

Increased overhead
If you lose fragment, you lose entire packet
Sometimes you don’t know fragmentation is happening

189
Q

Why is it sometimes necessary to manually configure MTUs?

A

Because it is difficult to the know MTU for an entire path. And automated methods are often inaccurate (especially when ICMP is filtered for security reason). Fortunately, MTUs don’t need to be configured often. Usually once is enough.

[Unclear what he means by “entire path.” Through the OSI layers?]

190
Q

The default Ethernet MTU size is ______,

A

1,500 bytes

[Be careful. This refers to max size of an IP packet or other payload that fits inside an Ethernet Frame. The Ethernet Frame itself will be a bit bigger due to headers]

191
Q

What size might you expect an Ethernet Frame to be if it contains an IP packet that is 1,500 bytes?

A

1,518 bytes (Standard Ethernet header of 14 bytes and FCS of 4 bytes at the end)

192
Q

What are two primary concerns when troubleshooting MTUs?

A

1) Tunneled traffics (e.g. VPNs). Because you need to put additional headers around your data. Tunnel may be smaller than your local Ethernet segment.
2) Some apps don’t want their data fragmented. Might send packets with a Don’t Fragment (DF) set in IP header

193
Q

What’s a good troubleshooting method for figuring out the largest MTU you can use?

A

ping -f -l 1472 8.8.8.8

-f means don’t fragment
-l specifies length
The IP is Google’s DNS server

Just keep lowering the length until the ping succeeds.

194
Q

What is network segmentation, and why might it be used?

A

Dividing a computer network into smaller physical or logical components. Helpful for security, performance, and separating different logical areas of a network.

(May also be referred to as network segregation, network partitioning, and network isolation)

195
Q

What is a LAN?

A

A local area network (LAN) is a collection of devices connected together in one physical location, such as a building, office, or home. A LAN can be small or large, ranging from a home network with one user to an enterprise network with thousands of users and devices in an office or school.

Regardless of size, a LAN’s single defining characteristic is that it connects devices that are in a single, limited area.

196
Q

What is a VLAN?

A

A virtual local area network (VLAN) is a logical group of workstations, servers and network devices that appear to be on the same LAN despite their geographical distribution. A VLAN allows a network of computers and users to communicate in a simulated environment as if they exist in a single LAN and are sharing a single broadcast and multicast domain.

[Another definition I saw somewhere: any broadcast domain that is segregated and isolated at the data link layer OSI layer 2]

197
Q

What are some reasons for using a VLAN?

A

VLANs are implemented to achieve scalability, security and ease of network management and can quickly adapt to changes in network requirements and relocation of workstations and server nodes.

198
Q

What is a 802.1Q Trunk, and why is it necessary?

A

An 802.1Q Trunk is a single physical connection between two switches that allows for numerous VLANs to be transmitted over that connection. (Think how a single tree trunk can support numerous branches.)

Without a trunk, having VLANs on multiple switches wouldn’t scale well. There simply aren’t enough available interfaces / ports.

199
Q

802.1Q is often abbreviated as _________.

A

Dot1q

200
Q

Prior to 802.1Q, there was a trunking protocol called _______ which is no longer used.

A

ISL (Inter-Switch LInk

201
Q

In terms of how it passes data, 802.1Q Trunking involves taking a normal _______ and adding an additional _______, which includes a _______ and _______.

A

Ethernet Frame
VLAN header field
TPID (Tag Protocol Identifier) (Identifies protocol)
VLAN ID (Identifies destination)

202
Q

A VLAN header field is ______ bits in length. It contains a TPID, which is _____ bits long. And a VLAN ID, which is ______ bits long. This allows enough ids for ______ VLANs per trunk.

A

32 bits long
16 bits long
12 bits long
4,094 VLANs per trunk

[The remaining 4 bits is for Quality of Service (QoS)]

203
Q

Describe how Cisco assigns VLAN IDs.

A

Normal Range: 1 to 1,005
Extended Range: 1,006 to 4,094
Reserved: 0 and 4,095

204
Q

STP stands for _____________.

A

Spanning Tree Protocol

205
Q

What is the purpose of STP?

A

Spanning Tree Protocol (STP) prevents loops on switched networks. Loops occur when two switches are connected with more than one cable, allowing them to send traffic back and forth forever (or until a cable is pulled). This can bring down a network.

206
Q

Spanning Tree Protocol (STP) is IEEE Standard ______.

A

8021.D

[“D” is for “what dumbass plugged in a second cable?”]

207
Q

There is only one _______ designated on any STP network. And on all the other switches, there is one interface designated as _______, which is the interface located __________.

A

root switch
root port
closest to the root switch

208
Q

What are the three types of interfaces configured automatically through STP?

A 
Root Port (RP) - Allows traffic to traverse this particular interface
Designated Port (DP) - The other interfaces on switch that allow traffic
Blocked Port (BP) - Any interface on a switch that might create a loop
209
Q

When a switch’s port has been configured to use STP, it can be in five different states. What are they?

A

Blocking: All traffic is stopped and port does not participate in frame forwarding. When initializing, this is the default state for all ports. (20 seconds)

Listening: If a port is a designated or root port, it moves to the listening state where it listens for changes in topology. No data transmission occurs at this point. Non-designated ports stay in the blocking state. (15 seconds)

Learning: Designated and root ports prepare to participate in frame forwarding and begin to populate the CAM table (i.e. MAC Address table). (15 seconds)

Forwarding: Designated and root ports are now actively forwarding frames.

Disabled: Administrator has turned off the port.

210
Q

What is a side effect of STP?

A

Traffic can take a longer, more circuitous path than we might expect, as it navigates around blocked ports.

211
Q

What happens in an STP network, when a change occurs, like a failed or disconnected switch?

A

STP has to converge the network and restructure which devices are connected through the Spanning Tree (and presumably which ports are active).

212
Q

RSTP stands for _____________.

A

Rapid Spanning Tree Protocol

213
Q

What is RSTP?

A

Much-needed update to STP, and the latest standard. It has a faster convergence process, reducing the wait time from 50 seconds to 6 seconds. Backwards compatible with STP. Can mix both in same network. Very similar processes.

214
Q

Rapid Spanning Tree (RSTP) is IEEE Standard ______.

A

8021.W

[“W” is still for “what dumbass plugged in a second cable?”]

215
Q

When you connect a switch to an Ethernet device, you need to make sure both have identical ________ and ________ settings. One way to ensure this is to enable __________.

A

speed (e.g. 10, 100, 1,000, or even faster)
duplex (e.g. half-duplex v. full-duplex)
auto-negotiate (v. manual)

216
Q

SVI stands for _____________.

A

Switch Virtual Interface (SVI)

217
Q

What is SVI?

A

A Switch Virtual Interface (SVI) is a virtual layer 3 interface on a switch that can route to other broadcast domains (or VLANs). It allows traffic to be routed between VLANs by providing a default gateway for the VLAN (without having an actual physical router).

[Remember that switches operate on layer 2]
[Confusing concept. Wasn’t mentioned by Prof. Messer]

218
Q

What is a Data VLAN?

A

A separate VLAN configured to transport traffic generated by end devices such as computers, servers, printers, access points, etc (i.e. user-generated data).

219
Q

What is a Management VLAN?

A

A separate VLAN for managing the switch from a remote location by using protocols such as telnet, SSH, SNMP, syslog etc. Normally the Management VLAN is VLAN 1, but you can use any VLAN as a management VLAN. Cisco recommends not to use VLAN 1 and not to use any VLAN that carries user data traffic as Management VLAN.

220
Q

What is a Default VLAN?

A

The primary VLAN which is loaded onto a managed switch after booting up. A new, out-of-the-box switch normally has all its ports assigned to VLAN 1 by default. This means that if you connect multiple devices on any number of physical ports on the switch, by default, all devices will be able to communicate with each other.

[From what I understand, Default VLAN will always be assigned to VLAN 1. Cannot be changed.]

221
Q

What is a Native VLAN?

A

A designated destination for untagged traffic. (i.e. traffic where the frames have not been encapsulated with 802.1q tags.) When a Cisco switch receives an Ethernet frame without a tag on an 802.1Q enabled interface, it will assume that it belongs to the native VLAN.

[I do wonder WHY you would have untagged frames in the first place]

[From what I understand, by default, the Native VLAN will be assigned to VLAN 1. But unlike the Default VLAN, this can be changed.]

[Native VLANs can pose a security risk]

222
Q

Explain the difference between an Access Port and a Trunk Port.

A

An access port is assigned to a single VLAN. The frames that arrive on an access port are assumed to be part of the access VLAN, and are therefore untagged. This port type is configured on switch ports that are connected to devices with a normal network card (e.g. a workstation).

A trunk port is connected to another switch. This port type can carry traffic of multiple VLANs. Therefore, frames must be tagged.

223
Q

What is a DMZ?

A

A demilitarized zone (DMZ) is a physical or logical subnetwork that contains and exposes an organization’s external-facing services to an untrusted, usually larger, network such as the Internet. (i.e. Allows people outside the network to access some resources, without accessing others.)

224
Q

PoE stands for _____________.

A

Power over Ethernet

225
Q

What is PoE?

A

Power over Ethernet (PoE) provides power over an Ethernet cable in addition to data. (i.e. One wire for both network and electricity.) Often used in VoIP phones, remote security cameras, and wireless access points. Helpful in difficult-to-power areas.

[Really started with VoIP phones. Folks wanted them to operate like old-fashioned landlines, which were powered by a single phone cable]

226
Q

PSE stands for _____________.

A

Power Sourcing Equipment

227
Q

What is PSE?

A

Power sourcing equipment (PSE) are devices that provide power on the Ethernet cable (PoE). They are available as End-spans or Mid-spans

228
Q

Explain the difference between Endspan and Midspan.

A

PSE devices are available as End-spans or Mid-spans. An End-span device is usually a network switch that can provide PoE power on each port. End-span PSEs typically are used in new installations where a new switch or router is required. Mid-span devices are often added to an existing network to add PoE capabilities.

229
Q

Explain the difference between Mode A and Mode B.

A

In PoE, Mode A refers to power being injected onto the Ethernet cable on pins 1,2,3, and 6 and is usually found in End-span devices. Mode B means injecting power onto pins 4,5,7, and 8 and is usually found in Midspan devices.

230
Q

Original PoE specification: IEEE _________
Wattage: ________
Max current: ________

A

PoE: IEEE 802.3af-2003
15.4 watts DC power
Maximum current of 350 mA

231
Q

Update PoE+ specification: IEEE _________
Wattage: _______
Max current: _______

A

PoE+: IEEE 802.3at-2009
25.5 watts DC power
Maximum current of 600 mA

232
Q

What is port mirroring?

A

Used on a network switch to send copy of network packets seen on one switch port (or an entire VLAN) to a network monitoring connection on another switch port. Commonly used for de-bugging / troubleshooting or intrusion detection.

aka network tap or switch port analyzer (SPAN)

233
Q

IPS / IDPS stands for _____________.

A

Intrusion Prevention System (IPS) or Intrusion Detection and Prevention System (IDPS)

234
Q

What is routing?

A

The process of selecting a path for traffic (i.e. IP packets) in a network or across multiple networks.

235
Q

When forwarding traffic, routers only know ______. Forwarding decisions are based on _________.

A

the next step or “hop”

destination IP address

236
Q

What is a routing table?

A

A database that keeps track of paths, like a map, and uses these to determine which way to forward traffic

237
Q

What are the two main kinds of routing?

A

static and dynamic

238
Q

What’s the difference between static and dynamic routing?

A

In static routing, the administrator determines the routes by manually updating routing tables.

In dynamic routing, the routing tables are updated automatically in (almost) real-time, as routers send route updates to other routers.

239
Q

What are the advantages and disadvantages of static routing?

A

Advantages:

    - Easy to configure and manage on smaller networks
    - No overhead from routing protocols (CPU, memory, bandwidth)
    - Easy to configure on sub networks (only one way out)
    - More secure - no routing protocols to analyze

Disadvantages:

    - Difficult to administer on larger networks
    - No automatic method to prevent routing loops (which are easy to create)
    - If there's a network change, you have to manually update the routes
    - No automatic rerouting if an outage occurs

[Obviously, these are reversed for dynamic routing]

240
Q

What is a default route?

A

The route that takes effect when no other route is available for an IP destination address. (i.e. when no specific address of a next-hop host is available from the routing table)

241
Q

A default route is also known as the __________.

A

“gateway of last resort”

242
Q

AS stands for _____________.

A

Autonomous System

243
Q

What is AS?

A

Autonomous System (AS) is a connected group of one or more IP prefixes run by one or more network operators which has a SINGLE and CLEARLY DEFINED routing policy. (As defined by RFC 1930, Section 3)

244
Q

IGP stands for _____________.

A

Interior Gateway Policy

245
Q

What is IGP?

A

Protocol used for exchanging routing information between gateways (commonly routers) WITHIN an autonomous system (AS).

246
Q

EGP stands for _____________.

A

Exterior Gateway Policy

247
Q

What is EGP?

A

Protocol used for exchanging routing information between gateways ACROSS different, neighboring autonomous systems (AS).

[Note: Can refer to a specific obsolete protocol used in the 1980s. Or can refer to a class of protocols, including BGP, that are still used today]

248
Q

Name three IPv4 Dynamic Routing Protocols used by IGP.

A
  • OSPFv2 (Open Shortest Path First)
  • RIPv2 (Routing Information Protocol version 2)
  • EIGRP (Enhanced Interior Gateway Routing Protocol) (Cisco systems)

[Should maybe make separate cards for each of these]

249
Q

Name three IPv6 Dynamic Routing Protocols used by IGP.

A

OSPFv3 (Open Shortest Path First)
RIPng (RIP next generation) (Routing Information Protocol)
EIGRP for IPv6 (Enhanced Interior Gateway Routing Protocol)

250
Q

BGP stands for _____________.

A

Border Gateway Protocol

251
Q

What is BGP?

A

Depending on how you define EGP, it is either:

a) The successor / replacement for EGP

or

b) The most popular type of EGP currently in use

252
Q

What are dynamic routing protocols?

A

Protocols that allow routers to share information about the network with other routers to allow them to select the best path to reach a destination. (Different routing protocols have different ways of determining best path, and of recovering from network changes like an outage.)

253
Q

Name three examples of dynamic routing protocols.

A

Distance-vector
Link-state
Hybrid

254
Q

How does a distance-vector routing protocol determine an optimal route?

A

The deciding “vector” is the “distance” of another network (i.e. how many “hops” away it is).

255
Q

What are the pros and cons of distance-vector routing?

A

Pros:

- Usually automatic (very little configuration)
- Good for smaller networks

Cons:

- A route with more hops (greater distance) might actually be faster!
- Doesn't scale well to very large networks
256
Q

What are three examples of distance-vector routing?

A

RIP, RIPv2, and Cisco’s EIGRP

257
Q

How does a link-state routing protocol determine an optimal route?

A

Concerned with quality and speed of connection (as opposed to “hops” or distance)

258
Q

What are the pros and cons of link-state routing?

A

Pros:

- Speed obviously
- Flexible and scalable, used most often in large networks.

Cons:
-Requires more memory and processing power than distance-vector

259
Q

What is an example of a link-state routing protocol

A

OSPF

260
Q

How does a hybrid routing protocol determine an optimal route?

A

A little link-state, a little distance-vector. (i.e. So it’s looking at distance or number of hops as well as connectivity / speed).

261
Q

What is an example of a hybrid routing protocol?

A

BGP (Border Gateway Protocol). Determines route based on paths, network policies, or configured rule-sets

262
Q

A subnet mask is used to divide an ________ into two parts. One part identifies _________, and other identifies ________.

A

IP address
network
host (computer)

263
Q

1 byte = ____ bits

A

8

264
Q

32 bits = _____ bytes

A

4

265
Q

An IPv4 address is ______ bits (or _____ bytes)

A

32

4

266
Q

An IPv6 address is ______ bits (or ____ bytes).

A

128

16

267
Q

What is the major advantage of IPv6 over IPv4?

A

Allows for a LOT more IP addresses, so much more scalable for all people / devices on the planet.

268
Q

Describe how to compress an IPv6 address.

A

1) Remove leading zeroes in each section

2) Abbreviate 2+ consecutive groups of zeroes with double colons (You can only do this once per address)

269
Q

In order to de-compress an IPv6 address, you need to remember what?

A

That an IPv6 contains 8 groups of 4 (You may not be able to expand the double colons without knowing this)

270
Q

What is dual-stack-routing?

A

A technique that involves running both IPv4 and IPv6 on a network. Interfaces are assigned multiple address types and router maintains both IPv4 and IPv6 routing tables.

271
Q

What is tunneling?

A

When one protocol encloses (i.e. encapsulates) in its datagram another complete data packet that uses a different communications protocol. Often used for privacy or security (e.g. VPN or SSH), but can also be used for handling IPv6 traffic on an IPv4 network (or vice versa).

272
Q

What is 6to4 tunneling?

A

An IPv6 transition technique that involves encapsulating IPv6 packets into IPv4 for transport across an IPv4 network.

[Notice it’s 6 TO 4, as opposed to 4 IN 6]

273
Q

What is 4in6 tunneling?

A

involves encapsulating IPv4 packets into IPv6 for transport across an IPv6 network.

[Notice it’s 4 IN 6, as opposed to 6 TO 4]

274
Q

A 6to4 address is immediately recognizable because it always begin with _______.

A

2002

e.g. 2002:CB00:71FF:0:fe64:3486:d398:3346

275
Q

6to4 tunneling requires a _______ and uses IP Protocol ______.

A

relay router

IP Protocol 41

276
Q

What are Taredo / Miredo?

A

Common IPv6 transition configuration that tunnels IPv6 through a NAT translated IPv4 network without need for a special IPV6 router.

Taredo is for Windows. Miredo is an open source version of Taredo for Linux, BSD Unix, and Mac OS X

277
Q

What is a node?

A

Basically any device on a network capable of sending, receiving, or forwarding data that has some form of identification (e.g. MAC address or IP Address).

Examples: Computers, routers, modems, switches, hubs, bridges, servers, and printers

278
Q

What’s the difference between a node and host?

A

A host is a type of node, usually an endpoint that provides data or a service, that has an IP address. (e.g. a server, possibly a printer, but not a router)

All hosts are nodes, but not all nodes are hosts.

279
Q

NDP stands for _____________.

A

Neighbor Discovery Protocol

280
Q

What is NDP in general?

A

Protocol used for IPv6 traffic that allows different nodes to advertise their existence to neighbors, and learn about existence (and availability) of neighbors.

281
Q

Instead of using broadcast like IPv4, NDP operates using _____ with ______.

A

multicast

ICMPv6

282
Q

Name five general services NDP provides for IPv6 devices.

A 
Automatic address configuration (SLAAC)
Duplicate address detection (DAD)
Router discovery (RS / RA)
MAC discovery
MTU discovery
283
Q

SLAAC stands for _____________.

A

Stateless Address Autoconfiguration

284
Q

What is SLAAC?

A

An NDP (Neighbor Discovery Protocol) service for IPv6 that automatically configures an IP address without a DHCP server.

285
Q

DAD stands for _____________.

A

Duplicate Address Detection

286
Q

What is DAD?

A

An NDP (Neighbor Discovery Protocol) service for IPv6 that prevents duplicate IP address.

287
Q

RS and RA stand for _____________.

A

Router Solicitation (RS) and Router Advertisement (RA)

288
Q

What is RS and RA?

A

Part of the NDP (Neighbor Discovery Protocol) service for IPv6 that involves router discovery.

289
Q

Describe how router discovery works in the Neighbor Discovery Protocol (NDP).

A
  • Routers send RS (router solicitation) messages to all IPv6 routers using ff02::2 address
  • Routers are listening for this. Will send back a unicast frame with RA (router advertisement) address of that local router

(Routers also send unsolicited RA messages from multicast destination of ff02::1)

290
Q

RAs are often used to transfer IPv6 address info, prefix value, and prefix length. What are the prefix value and length?

A

prefix value = IPv6 network

prefix length = Local subnet mask

291
Q

NS and NA stand for _____________.

A

Neighbor Solicitation (NS) and Neighbor Advertisement (RA)

292
Q

What is NS and NA?

A

Basically, it’s how devices in an IPv6 network discover the MAC addresses of other network devices so they can communicate. Because remember, IPv6 does not use Address Resolution Protocol (ARP).

293
Q

Briefly describe how NS and NA work.

A
  • Neighbor Solicitation (NS) - Sends out IPv6 address as multicast to get MAC address (Might also send out NS to test whether IP address is already taken or available)
  • Neighbor Advertisement (NA) - Device with that IPv6 address sends back MAC address
294
Q

What’s the fundamental difference between RS/RA and NS/NA?

A

RS/RA is for router discovery. NS/NA is for devices like workstations to find MAC address of other devices.

295
Q

What is traffic shaping (aka packet shaping)?

A

Controlling bandwidth usage (e.g. who uses it, when, and for what purpose). Involves setting higher priority for important apps.

[I believe it could be considered a QoS method]

296
Q

QoS stands for _____________.

A

Quality of Service

297
Q

What is QoS?

A

Describes the strategies used to manage and increase the flow of network traffic. Enables administrators to predict bandwidth use, monitor that use, and control it to ensure that bandwidth is available to the applications that need it most (e.g. latency sensitive apps)

298
Q

What is the difference between latency sensitive and latency insensitive apps? Give examples.

A

Latency sensitive apps need bandwidth for quick delivery, and are therefore prioritized by QoS methods. (e.g. videoconferencing, streaming video, and VoIP)

Latency insensitive apps would include web traffic, faxing, or large backups via FTP.

299
Q

Two popular standards / methods of implementing QoS are ______ and _______.

A

CoS
DiffServ

[Messer refers to these as standards of QoS. But one of my books refers to them as components of QoS. A little unclear]

300
Q

CoS stands for _____________.

A

Class of Service

301
Q

What is CoS?

A

A QoS standard / component that differentiates types of payloads being transmitted. Usually applied in intranet (not from ISP). Involves Ethernet frame headers in 802.1Q trunks. So between switches in OSI Layer 2 (Data Link).

[See also DiffServ]

302
Q

DiffServ stands for _____________.

A

Differentiated Services

303
Q

What is DiffServ?

A

A QoS standard / component that differentiates types of payloads being transmitted.
QoS bits are enabled in the IPv4 header by routers in OSI Layer 3 (Network).

[See also CoS]

304
Q

DSCP stands for _____________.

A

Differentiated Service Code Point

305
Q

What is DSCP?

A

These are the QoS values placed in the DS (Differentiated Services) field in an IPv4 header by DiffServ.

306
Q

NAT stands for _____________.

A

Network Address Translation

307
Q

What is the purpose of NAT?

A

A process/technology where a router translates an internal host’s private IP address into its public IP address for outgoing traffic, and vice versa for incoming traffic.

Allows many computers to “hide” behind a single IP Address. Important due to IPv4 address pace being exhausted. (Also helps with security.)

308
Q

We use _____ IP addresses inside a network, which are then NATed to ______ IP addresses when connecting to the Internet. When there’s a response from outside the network, ______ IP addresses are NAT translated back to ______ IP addresses.

A

private
public
public
private

[NOTE: NAT allows you to use whatever addressing scheme you want, but common to use private IP addresses]

309
Q

_______ IP addresses are not routable across the Internet.

A

Private

310
Q

RFC 1918 designates the following ranges as private IPv4 addresses.

A
  1. 0.0.0 - 10.255.255.255
  2. 16.0.0 - 172.31.255.255
  3. 168.0.0 - 192.168.255.255
311
Q

PAT stands for _____________.

A

Port Address Translation

312
Q

What is PAT?

A

A common type of NAT where all systems on a LAN are translated to the same IP address, but with different port number assignments. And then the router will place its own port number on the outward-facing IP address. (e.g. 10.10.20.50:3233 -> 94.1.1.1:1055)

The router maintains a NAT Table to track its translations so inbound replies can be transmitted back to original client.

313
Q

PAT is also known as ________.

A

NAT overload

314
Q

What is the main shortcoming of PAT?

A

The NATed addresses are dynamic / temporary, and communication with Internet must be initiated by internal client. So not good for services that need to be permanently accessible from Internet. (e.g. email or web server)

[I think this is accurate]

315
Q

SNAT stands for _____________.

A

Static Network Address Translation

316
Q

What is SNAT?

A

A one-to-one mapping of a private IP address to a static unchanging public IP address. This enables an internal system, such as a mail server, to have a private IP address and still be reachable over the Internet.

[This has more to do with incoming traffic. Does not have the same dynamic / temporary shortcomings of PAT. Note that ports are not used, so it’s a one-to-one translation, meaning you DO need to use additional public IP addresses. Wasteful in that regard.]

[There’s also Dynamic NAT, which does the same kind of one-to-one mapping, but it draws IP address from pool of first available. Deals more with outbound traffic. Not to be confused with Destination NAT.]

317
Q

DNAT stands for _____________.

A

Destination Network Address Translation

318
Q

What is DNAT?

A

A kind of NAT that provides 24x7 access from outside network to a service hosted inside network. Used to direct authorized inbound traffic to appropriate services or apps on network. (e.g. Web server, gaming server, security system, etc.). We map / configure external IP + port number to an internal IP + port.

[So this is about incoming traffic. Interestingly, Messer says SNAT and DNAT are basically synonyms. Another book distinguishes them, but it’s not clear how. This appears to use port numbers, whereas SNAT doesn’t. Very confusing]

319
Q

DNAT is also known as ________.

A

Port Forwarding

[As in Destination NAT. Not Dynamic NAT]

320
Q

ACL stands for _____________.

A

Access Control List

321
Q

What is an ACL?

A

A list of allowed or nonallowed services, ports, websites, etc.

  • A way to allow or disallow traffic to parts of our network (i.e. a packet filter)
  • Can be used for NAT, QoS, etc.
  • Commonly configured in router
  • Can apply to ingress traffic (incoming), egress traffic (outgoing), or both
  • Can evaluate on different criteria (e.g. source IP, destination IP, TCP and UDP port numbers, ICMP, etc.)
322
Q

______ is a networking device, either hardware or software based, that can protect internal networks from public networks and control access between specific network segments. Its rules can be considered an ACL.

A

Firewall

323
Q

What are tuples, and what are their relationship to firewalls?

A

Tuples are an ordered list, like an array, except it’s immutable (unchanging). They’re basically the columns in a firewall policy used to determine whether to block or allow traffic (e.g. Source IP, destination IP, port number, time of day, application, etc.).

[pronounced “tupple”]

324
Q

A firewall follows a logical path through its rules, looking for a match to ____, usually ordered _____ to ______.

A

allow
top to bottom

[Once it finds a match, it will allow and skip the rest]

325
Q

Firewall rules can be very general or very specific. Usually, the ______ rules are at the top.

A

Specific

326
Q

What does “implicit deny” mean in regards to firewalls?

A

It means default denial. Most firewalls are written with a denial at the bottom, so if you’ve gone through every single allow rule, and there’s no match, access is denied.

327
Q

Give an example of what a row in a web server firewall ruleset might look like.

A

Rule Number Remote IP Remote Port Local Port Protocol Action
1 ALL ANY 22 TCP Allow

328
Q

What is circuit switching? Give examples.

A

A dedicated, physical transmission channel (i.e. circuit) is established between endpoints before data ever passes, and reserved until disconnected. (Basically always uses phone lines?)

Examples:

  • POTS / PSTN (e.g. landline phone technologies)
  • T1 / T3 (or E1 / E3 in Europe) (creates circuit between two sites)
  • ISDN (uses phone number to call another ISDN modem)

[See also: packet switching]

329
Q

What are the advantages / disadvantages of circuit switching?

A

Advantages: Connection is always there if you need it. More reliable. Better audio quality. Generally more secure. (Communication paths are exclusive to two parties)

Disadvantages: Inefficient use of network bandwidth. Networks more expensive to use, build, maintain

330
Q

POTS stands for _____________.

A

Plain Old Telephone Service

331
Q

PSTN stands for _____________.

A

Public Switched Telephone Network

332
Q

ISDN stands for _____________.

A

Integrated Services Digital Network

333
Q

What is packet switching? Give examples.

A

Messages are broken into smaller pieces called packets and sent across a network shared with everyone. Each packet is assigned a source, destination, and intermediate node addresses. (Basically always uses Internet?)

Examples:

  • SONET (Synchronous Optical Network) [fiber optics]
  • ATM (Asynchronous Transfer Mode) [Actually both packet and circuit switching??]
  • DSL (Digital Subscriber Line) [
  • Frame relay
  • MPLS (Multiprotocol Label Switching)
  • Cable modem
  • Satellite
  • Wireless network (home)

[Hopefully Messer discusses some of these later?]

334
Q

What are the advantages / disadvantages of packet switching?

A

Advantages: Transmits data fastest way possible. Multiple users share same network. More efficient use of bandwidth. Cheaper networks.

Disadvantages: Poor connections and call quality. More vulnerable to security threats. Unpredictable latency

335
Q

SDN stands for _____________.

A

Software Defined Networking

336
Q

What is SDN?

A

An approach to networking that allows network administrators to programmatically manage network behavior dynamically via open interfaces and provide abstraction of lower-level functionality.

SDN (software-defined networking) centralizes the control of data flow by using software. In this process determinations that were traditionally handled by routers and switches, are now handled by the SDN controller. The SDN controller integrates the functions of device configuration and device management into a single software interface. This simplifies device management as every physical or virtual device can be accessed, monitored and configured. The software interface or dashboard allows administrators to control devices simultaneously as a group, making it a clear alternative to individual device access. SDN will play a major role in Cloud technologies.

337
Q

What are some of the advantages of SDN?

A
  • Agile / flexible: Changes can be made dynamically on the fly at any time. (e.g. More capacity can be provided on network where it’s needed)
  • Centrally managed: One central console. Don’t need to login multiple places. Can control entire network from one screen

-Programmatically configured: Automation. No human intervention needed (e.g. if network becomes congested or needs more resources, can
be deployed automatically)

-Open standards / vendor neutral: A standard interface to the network (i.e. For the software part of it)

338
Q

What is Distributed Switching?

A

Allows for a single physical switch to manage multiple virtual hosts, which each contain things like web server, database server, test server, etc. Allows for separation of these virtual devices into their own VLANs. You can group these resources, so web servers are on their own VLAN, database servers on another, etc.

Provides a centralized control point for VMs and virtual server clusters across multiple points. This simplifies network management and reduces errors. On each physical host, an agent is installed. A supervisor module on the distributed switch then controls the hosts.

[Had a VERY hard time finding decent info on this. Not sure how accurate this is.]

339
Q

h.323 port?

A

tcp/1720

Network+ (8 decks)

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