Network+ Flashcards
Number of subnets
2^zeros borrowed from classful (from the left).
Number of hosts per subnet
2^(host bits) - 2. Host bits are zeros from the right side.
802.11a
“a” for the beginning. It uses 5 GHz frequency, which has shorter range (in my head that equates to weaker) than 2.4 GHz. Just remember 5 GHz and 5 for 54 Mbps.
802.11b
B for better range. It uses 2.4 GHz frequency, which has longer range but lower speed. Just remember 2.4 GHz and 2.4 has 2 numbers, and so does 11 Mbps.
802.11g
G, better than “b”, which rhymes with g. It uses the same 2.4 GHz as “b” and it has 54 Mbps. Since you’re upgrading from b, whose flaw was its throughput, remember that “a” was 54 Mbps too, and that will help you remember that “g” is also 54 Mbps.
802.11n
It uses both frequencies (2.4 GHz and 5 GHz). The way I remember this is (a n g) (as in “n” = “and”). 802.11n has much higher speed (600 Mbps). Just remember N as negative, which could also be said as 2 subtract 8 (the 8 from 802.11 and the 2) to get 6. (6 reminds you of the throughput of 600 Mbps). It also introduces MIMO, which is easy to remember because M comes before N.
802.11ac
The way I remember this, I remember 802.11a frequency is 5 GHz, then you can remember AC is also 5 GHz (a being what ties them together). However, AC uses MU MIMO. Just remember AC is the first 802.11 standard with multiple letters (AC), which will then remind you of multi (i.e. MU(user) MIMO). The 8 in 802 will remind you that there are 8 channels (the multi should trigger your memory for the 8). Each channel will support a throughput of 867 (notice the 8), which comes out to roughly a total of 7 GB.
802.11ax
Last but not least, probably the easiest one to remember, 802.11ax. I basically just remember that this is the most recent one, so it’s going to bring them all together. If you need help remembering, an “X” looks like two arrows pointing towards each other (i.e. bringing them together), which reminds you that 802.11ax can do both frequencies. You’re also using multi-MIMO. I usually just remember X as 10, because your max throughput with all channels is 10 GB (9.6).
IP Classes
IP addresses belonging to class A ranges from 0.0.0.0 – 127.255.255.255.
IP addresses belonging to class B ranges from 128.0.0.0 – 191.255.255.255.
IP addresses belonging to class C range from 192.0.0.0 – 223.255.255.255.
Class D does not possess any subnet mask. IP addresses belonging to class D range from 224.0.0.0 – 239.255.255.255.
IP addresses belonging to class E are reserved for experimental and research purposes. IP addresses of class E range from 240.0.0.0 – 255.255.255.255. This class doesn’t have any subnet mask. The higher-order bits of the first octet of class E are always set to 1111.
Special range IP addresses
169.254.0.0 – 169.254.0.16 : Link-local addresses.
127.0.0.0 – 127.255.255.255 : Loop-back addresses.
0.0.0.0 – 0.0.0.8: used to communicate within the current network.
Private IP Class
The range for Class A IP addresses is 10.0.0.0 to 10.255.255.255. This class is used for large networks and is commonly used in large organizations and enterprises.
The range for Class B IP addresses is 172.16.0.0 to 172.31.255.255. This class is used for medium networks and is often used in schools, universities, and businesses.
The range for Class C IP addresses is 192.168.0.0 to 192.168.255.255. This class is used for smaller networks and is commonly used in small office or home networks (SOHO networks).
ping
Testing reachability using ICMP.
ipconfig/ifconfig/ip
Determine computer/s network configuration (TCP/IP).
ipconfig: Windows
ifconfig: Linux
ip: Linux
The ip command has more features and a broader scope than ifconfig. For example, ip can add or remove IP addresses, configure routes, and manage ARP tables. Ifconfig is limited to basic configuration tasks.
nslookup/dig
Look up information from DNS servers.
nslookup: quick one-line DNS resolution results.
dig: more thorough DNS results with better formatting and readability
traceroute/tracert
Determine the route a packet takes to a destination.
arp
View MAC addresses based on IP addresses.
netstat
Shows details about active network connections, including the protocol, IP addresses, port numbers, and connection state, primarily used for troubleshooting network issues on a single machine.
nmap
Actively scans a network to identify live hosts, detect open ports, and gather information about services running on those ports, used for network mapping and security auditing.
route
A utility that allows users to view and manipulate the IP routing table on their computer.
telnet
A great utility for checking a port or application.
tcpdump
Linux. Windows has its own version called windump. Capture packets from the command line.
Range of well-known TCP/UDP ports
Below 1024.
Windowing
A mechanism used by protocols like TCP (Transmission Control Protocol) to manage the flow of data between two devices by dividing data into smaller segments called “windows,” allowing the sender to transmit a certain amount of data before needing an acknowledgment from the receiver, preventing network congestion and ensuring reliable data delivery.
Fast Ethernet Mbps
100
F-connector is often used for
Cable TV/Cable modem
EUI-64 in IPv6 permits automatic generation of
host portions of addresses
Basis for the PAT configuration
IP address on the physical outside interface
Multi-tenancy
Using a single physical server for multiple clients.
Firewall: Stateful vs Stateless
Stateful: Stateful firewalls maintain a state table that records information about ongoing network connections.
Stateless: A type of firewall that filters network traffic based on individual packets without storing information about the state or context of connections.
Split horizon and Poison reverse
Distance vector routing protocols preventing routing loops.
Split horizon: a network protocol technique that prevents routing loops by stopping routers from advertising routes back to the interface they were learned from.
Poison reverse: prevents routing loops by informing neighboring routers that a route is unreachable by setting its metric to infinity,
