Block 4 Networking Flashcards
1
Q
Hub
A
Operates at the physical layer and does not separate collision domains
2
Q
Repeater
A
Operates at the physical layer and boosts signals, twisted pair max length of 100m
3
Q
Modem
A
Operates at the physical layer and converts from analog to digital
4
Q
Media converter
A
Operates at the physical layer and allows connection between different media types
5
Q
NIC
A
Network Interface Controller, allows physical and data link layer connections
6
Q
Bridge
A
Operates in the data link layer, reduces amount of traffic on a LAN by dividing collision domains
7
Q
Switch
A
Operates at the data link layer, each port is a collision domain
8
Q
Wireless access point
A
Allows wireless access to wired network
9
Q
Router
A
Operates at the network layer, connects two or more networks by forwarding packets between them, breaks up broadcast domains
10
Q
How do routers select the best path for network packets
A
Using it’s routing table
11
Q
Firewall
A
Operates between the network and transport layers, allows monitoring and control of network traffic
12
Q
How do firewalls work?
A
They act on pre-determined rules to enable a barrier between trusted and untrusted connections and devices
13
Q
What are the layers in the OSI model?
A
Physical, Data Link, Network, Transport, Session, Presentation, Application
14
Q
What are the layers in the old TCP/IP Model?
A
Link, Internet, Transport, Application
15
Q
What are the layers in the new TCP/IP model?
A
Physical, Data Link, Network, Transport, Application
16
Q
What is the PDU of the application layer?
A
Data
17
Q
What is the PDU of the transport layer?
A
Segment (TCP), Datagram (UDP)
18
Q
What is the PDU of the network layer?
A
Packet or IP Datagram
19
Q
What is the PDU of the data link layer?
A
Frame
20
Q
What is the PDU of the physical layer?
A
Bit
21
Q
What are some application layer protocols and services?
A
HTTP/S, POP3, SMTP, DNS, FTP, Telnet, SSH
22
Q
What are some transport layer protocols and services?
A
TCP, UDP
23
Q
What are some network layer protocols and services?
A
IP, ARP, ICMP, IPv4/Ipv6
24
Q
What are some application/presentation/session layer devices?
A
Clients, servers, application layer security appliances
25
What devices operates between the transport and network layers?
Firewall
26
What are some network layer devices?
Router, multilayer switch
27
What are some data link layer devices?
Switch, bridge, wireless AP
28
What device operates between the data link and physical layer?
The NIC (Network Interface Controller)
29
What are some physical layer devices?
Hub, modem, repeater, cables, media converters
30
What are the different network topologies?
Bus, ring, star, mesh, hybrid
31
In a bus topology how many nodes will a failure affect?
All of them
32
Are rings unidirectional or bidirectional?
They can be both but if it's unidirectional a secondary link is needed for redundancy
33
What two devices can be used to set up a star topology?
Switch and hub
34
If a star topology is set up using a switch it's a logical what?
Star
35
If a star topology is set up using a hub it's a logical what?
Bus
36
What are the advantages of a mesh topology?
Extremely reliable, provides redundancy and fault tolerance between devices
37
What are the disadvantages of a mesh topology?
High administrative overhead, full mesh requires exponentially more cabling
38
What are the advantages of a hybrid topology?
Flexible, reliable, increased fault tolerance, easy to expand, network faults can be easily diagnosed and corrected without affecting the rest of the network
39
What are the disadvantages of a hybrid topology?
Difficult to manage and expensive
40
Circuit-Switched Network
A sequence of links between two nodes is determined ahead of the actual communication, data is sent as a stream of bits
41
Packet Switched Network
Routers determine packet addressing, processes digital signals and routes information through multiple pathways
42
In which type of network does each data unit know the entire path address which is provided by the source?
Circuit switched
43
Resource reservation is a feature of what type of network?
Circuit switched
44
In which type of network does each data unit know only the final destination address and the path is determined by routers?
Packet switched
45
Virtual Circuit
The process of providing a connection oriented service between two hosts over a packet-switched network (TCP)
46
Supernetting
Routing protocols can summarize address of several networks into one
47
What are some advantages of supernetting?
Shrinks the routing table, improvers routing performance, quicker to send
48
Discontiguous Network
Two networks of the same classful networks are separated by a different network address
49
What is a limitation of older routing protocols?
The do not support discontiguous networks
50
What are the steps in Variable Length Subnet Masks (VLSM)?
- Order host requirements from largest to smallest
- Determine number of host bits needed
- Create smallest subnet needed for that host requirement
- Continue until all host requirements are met
51
What are some features of IPv4 that don't exist in IPv6?
Subnet masks, network address, and broadcast address
52
What are the first 48 bits of an IPv6 address reserved for?
Networking/routing (usually from ISP)
53
What are bits 49-64 of an IPv6 address used for?
Subnets
54
What are the last 64 bits of an IPv6 address used for?
Hosts
55
In IPv6 once you determine the number of subnet bits you need what number do you add that to to get the mask?
48
56
Who developed the TCP/IP network model?
Defense Advanced Research Project Agency (DARPA)
57
Who developed the Open Systems Interconnect (OSI) model?
The International Organization for Standardization (ISO)
58
When was the TCP/IP model adopted?
The 1990s
59
Who developed the TCP/IP model?
It was a DoD led effort
60
What does TCP/IP use to define standardization protocols?
Request for Comments (RFC)
61
What is a Protocol Data Unit (PDU)?
Its a generic term for a unit of information being transmitted at a specific layer
62
What do application layer protocols do?
Provide services to the application software running on a computer, defines how programs interface with transport layer, functions include identifying communication partners, determining resource availability, and synchronizing communication
63
What is the DHCP protocol used for?
Assigning IP addresses
64
What ports does DHCP usually use?
UDP port 67 (client to server, broadcast)
UDP port 68 (server to client, unicast)
65
What will the server assign in DHCP?
IP address, lease, subnet mask, default gateway and possibly other options
66
DHCP uses what process?
Discover, Offer, Request, Acknowledge (DORA)
67
What is the Discover step in the DORA process?
Sent by the DHCP client to find a DHCP server (broadcast)
68
What is the Offer step in the DORA process?
Sent by the DHCP server to offer IP address and other parameters (unicast)
69
How do DHCP servers detect conflicts?
By using pings. They ping the address and if someone is using it the server receives a response
70
What is the Request step in the DORA process?
Reply from a client to the server accepting the offer. Contains server ID option so all DHCP servers know an offer was accepted (broadcast)
71
What is the Acknowledge step in the DORA process?
Sent by the DHCP server to acknowledge final phase and deliver DHCP lease information (unicast). Client will ARP new IP to verify it doesn't overlap another
72
DNS
- TCP/UDP - port 53
- Hierarchical naming system
- Translates domain names into IP addresses
73
True/False DNS is a world wide service?
True
74
HTTP
- TCP 80 [8008, 8080]
- Protocol for the internet
- Request/response
- In between client and server may be several intermediaries
75
What does HTTP use for reliability?
TCP
76
How are servers identified in http?
URIs and URLs
77
HTTPS
- TCP 443
- URI/URL scheme used to indicate a secure HTTP connection
- Encrypts with digital certificate
- If NTP is not synchronized cert signing can fail
- Self signed certs provide confidentiality but don't confirm identity
78
File Transfer Protocol (FTP)
- Default data TCP 20
- Control TCP 21
- Does not encrypt or protect data in transit
- Does not guarantee identity of sender or receiver
- Does provide authentication options
79
TFTP
- UDP port 69
- Very basic form of FTP
- Can only read and write files (or mail) from/to server
- No provisions for user authentication
- Typically used for storage and retrieval of Cisco IOS and Catalyst switch configuration files
80
TELNET
- Used for remote terminal connection
- TCP port 23
- Non secure
81
SSH
- Used for remote terminal connection
- TCP port 22
- Encrypted remote access
82
NTP
- UDP port 123
- Synchronize computer clock times in a network
- can use radio and satellite systems
83
Transport Layer Services
Provides services to higher layer protocols and communication session management between hosts
84
What are the transport layer services?
Transmission Control Protocol (TCP)
User Datagram Protocol (UDP)
85
What is the difference between TCP and UDP?
Stateful vs Stateless or Connection Oriented vs Connectionless
86
What are the two functions of TCP?
1. Flow control provided by sliding windows
2. Reliability provided by sequence numbers and acknowledgments
87
What does TCP guarantee?
- Delivery of data
- Guarantees packets will be delivered in the same order in which they were sent
88
What are some features of TCP?
- Breaks messages into segments
- Resends anything that is not received
- Reassembles messages from the segments
- TCP supplies a virtual circuit between end-user applications
89
What are the first 16 bits of a TCP header?
Source port
90
What are bits 16 to 31 of a TCP header?
Destination port
91
What are bits 32 to 63 or a TCP header?
Sequence number
92
What are bits 64 to 95 of a TCP header?
Acknowledgment number
93
What are bits 112 to 127 of a TCP header?
Window size
94
What are bits 128 to 143 of a TCP header?
Checksum
95
How does TCP synchronize?
- Initial Sequence Numbers (ISN)
- SYN (for synchronize) control bit
- ACK (for acknowledge) control bit
- Three was handshake
96
TCP Window Size
- Flow control mechanism
- # of messages transmitted before ack needed
- More efficient use of bandwidth
97
User Datagram Protocol (UDP)
Message based connectionless protocol, non-guaranteed datagram delivery
98
What is the UDP header length?
64
99
What are the first 16 bits of the UDP header?
Source port
100
What are bits 16 to 31 of the UDP header?
Destination port
101
What are bits 32 to 47 of the UDP header?
Length
102
What are bits 48 to 63 of a UDP header?
Checksum
103
What must be depended on for reliability when using UDP?
Upper layer protocols
104
What are some protocols that use UDP?
TFTP, SNMP, DNS client requests
105
What allows multiple programs to share one connection simultaneously?
Ports
106
What identifies which specific services/applications are available for clients to connect to and use?
Open TCP/UDP ports
107
What is port 80 normally used for?
HTTP using TCP
108
What is port 443 normally used for?
HTTPS using TCP
109
What is port 22 normally used for?
SSH using TCP
110
What is sockets purpose?
They're used to track different concurrent network sessions
111
What do sockets consist of?
IP address, Transport protocol (TCP or UDP), and port number (source and destination)
112
What is the range of well known/system ports?
0-1023
113
What organization are the well known/system ports controlled by?
Internet Assigned Numbers Authority (IANA)
114
What is the range of user/registered ports?
1024-49151
115
What is the range for dynamic/ephemeral ports?
49152-65535
116
OS's Windows XP and older can only use dynamic ports up to what number?
5000
117
What is it called when different layers work together on the same system?
Adjacent-layer interaction
118
What is it called when one system communicates with the same layer on a different system?
Same-layer interaction
119
What is the main protocol of the network layer?
Internet protocol (IP)
120
What are common protocols of the network layer?
IPv4, IPv6, ARP, ICMP
121
Are IP packets related to each other?
No they are treated as independent units without any relation to any other unit of data
122
122
What is data encapsulated at the network layer called?
IP payload
123
What are the maximum and minimum lengths of an IP header?
60 bytes max, 20 bytes min
124
What are the two main parts of an IPv6 packet?
The header and the payload
125
How long is an IPv6 header?
The first 40 bytes
126
What is the first thing in an IPv6 header?
A 4 bit tag indicating the version
127
What are bits 4-11 of an IPv6 header?
Traffic class
128
What are bits 12-31 of an IPv6 header?
Flow label, used for Q0S management
129
What are bits 32 to 47 of an IPv6 header?
Payload length
130
What are bits 48 to 55 of an IPv6 header?
Next header
131
What are bits 56 to 63 of an IPv6 header?
Hop limit
132
What are bits 64 to 191 of an IPv6 header?
Source address
133
What are bits 192 to 319 of an IPv6 header?
Destination address
134
What are the two parts of the contents of an IPv6 packet?
Extension header and upper layer protocol data unit (payload)
135
What are IPv6 extension headers used for?
To move fields that are variable length from IPv4 headers into the packet
136
Address Resolution Protocol (ARP)
- Maps a known IP address to a MAC sub-layer address
- Allows communication on ethernet LAN
- Determines a destination address for a packet by checking the ARP cache table
- Sends broadcast if the destination is unknown
137
What is local ARP?
Resolve an address when both host and destination share the same media or wire
138
ICMP
- Provides feedback about problems in the network
- Usually formed from a normal IP packet that has generated an ICMP response
139
How does data link encapsulation and addressing (MAC) handle errors?
It detects them but does not recover
140
Frame Check Sequence (FCS)
Provides a method for receiving NIC to determine whether the frame experienced transmission errors
141
What happens if the data link layer detects an error?
The receiver discards the frame
142
What are the primary protocols of the data link layer?
Ethernet and PPP
143
Physical Address (MAC)
- Hardware address, ethernet address
- Burned into card
- Can't be changed but can be spoofed
144
What is the breakdown of MAC addresses?
- 48 bits in length
- First 6 hex digits identify the manufacturer or vendor - Organizational Unique Identifier (OUI)
- Remaining 6 hex digits identify the interface serial number
145
Ethernet Frame
Encapsulated data defined by the network access layer
146
What are the parts of an ethernet frame?
Preamble, Start Frame Delimiter (SFD), Destination MAC, Source MAC, Type, Data and Pad, Frame Check Sequence (FCS)
147
Ethernet (IEEE 802.3)
Defines standards for physically connected Local Area Networks (LAN)
148
Spanning Tree Protocol (STP)
Prevents frame loops within a switched network
149
Physical Layer
Encodes a signal onto a medium to transmit the frame
150
What are some IEEE 802.3 media types?
Coaxial cable, twisted pair cable, UTP & STP, connectors & wiring schemes, fiber optic cable
151
What are the types of Twisted Pair Cabling?
Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP)
152
How many pairs of copper wire are in twisted pair cable?
4
153
Why are twisted pair cables twisted?
To reduce EMI
154
What is the standard ending for twisted pair cable?
RJ-45 connectors and ports
155
Straight Through Cables
Connects "unlike" devices
156
Crossover Cables
Connects "like" devices
157
What are the two modes of fiber?
Single mode fiber (SMF) and multi mode fiber (MMF)
158
Which is cheaper, single mode fiber or multi mode fiber?
Multimode fiber
159
Encapsulation
The process of adding headers (and sometimes trailers) around data
160
De-encapsulation
The process of inspecting and removing headers to process data inside
161
Institute of Electrical and Electronics Engineers (IEEE)
Non-profit professional association for the advancement of technology
162
What are the 802 categories?
Authentication, ethernet, wireless, WPAN, Bluetooth, WMAN
163
802.1x
Authentication mechanism for devices wishing to connect to LAN/WLAN, provides protection for other types such as remote access and VPN
164
What 802 category deals with authentication?
802.1x
165
802.3
Ethernet, defines standard for physically connected networks, most common implementation of linear bus topology
166
What 802 category deals with ethernet?
802.3
167
CSMA/CD
- Carrier: the network signal
- Sense: the ability to detect
- Multiple Access: all devices have equal access
- Collision: what happens if devices send at once
- Detection: how to handle collision
168
How does the CSMA/CD process work?
- Device waits until line is free but collisions still occur
- If a collision occurs randomly select a hold time then retransmits
169
What are the different ethernet address categories?
Unicast, broadcast, multicast
170
Switch Address Learning
- an ethernet switch learns the MAC address of devices attached to each of its port
- the source MAC address to a physical port mappings are stored in a MAC database (CAM table, MAC address table)
171
Forward/Filter Decision
- Switch receives a frame
- Consult the MAC database
- If found the frame is sent only to that port
- If not found the frame is flooded out all other ports
172
Collision Domain
Domain in which a frame sent by one NIC could result in a collision with a frame sent by another NIC
173
Broadcast Domain
Domain in which a broadcast frame sent by one NIC is received by all other NICs
174
What are the consideration when designing a LAN?
- Collison/broadcast domains
- Total devices per collision domain
- Issue of broadcasts
- Segment large LAN w/routers
175
802.11
Wireless, a set of MAC and physical specification for implementing Wireless Local Area Network (WLAN)
176
What 802 category deals with wireless?
802.11
177
IPv4 Addresses
Each source and destination address field contains a 32 bit address
178
Private IP Addresses
- Non-routable on public networks or internet
- 1 range per class
179
What is the private IP range for Class A networks?
10.0.0.0/8
180
What is the private IP range for Class B networks?
172.16-31.0.0/12
181
What is the private IP range for Class C networks?
192.168.0.0/16
182
What are the types of special purpose IPv4 addresses?
Loopback and APIPA
183
What is a loopback address?
- 127.0.0.1/8
- Represents this computer
- Logical not physical
184
What is the APIPA address?
- 169.254.0.0/16
- An automatically assigned private IP address
- Allows host communication (LAN only) when no DHCP server exists or cannot be reached
185
What organization assigns classful IP addresses?
The American Registry for Internet Numbers (ARIN)
186
What are the benefits of IPv6?
- Increase the amount of IP addresses available
- Better security (IPSEC)
- Network Address Translation (NAT) optional
- Simpler header format
- More efficient routing
- Easier administration
187
What makes up a IPv6 address?
128 bits represented as 8 groups of 4 hex digits
188
IPv6 Abbreviation
- Consecutive zeros replaced with :: only once
- Leading zeros within a group can be removed
189
What is the IPv6 loopback address?
::1
190
::
Unspecified IPv6 address used for addressing purposes within software
191
Types of IPv6 addresses?
- Classified by scopes (where they can communicate)
- Global unicast (globally routable)
- Unique local address (same as private address in IPv4)
- Link local (routable within a broadcast domain)
- Interfaces can have multiple IPv6 addresses assigned to them (1 global/1 local)
192
::FFFF/96
IPv4 embedded into IPv6
193
::/128
Unspecified (0.0.0.0 IPv4 equivalent)
194
::1/128
Loopback (127.0.0.1 IPv4 equivalent)
195
FE80::/10
Link local (169.254.0.0/16 IPv4 equivalent)
196
FC00::/8, FD00::/8
Unique local (10.0.0.0/8 IPv4 equivalent)
197
2000::/3
Global Unicast (public IP IPv4 equivalent)
198
FF00::8
Multicast (224.0.0.0/4 IPv4 equivalent)
199
IPv6 Anycast
Typically used to locate the nearest server offering a specific service (DNS, DHCP, HTTP)
