Cheat Sheet (Ports, Troubleshooting, RAID, 802.11) Flashcards
Troubleshooting Step 1
Word: Identify
Identify the problem:
Question the user & identify user changes to computer & perform backups before making changes
Inquire regarding environmental/infrastructure changes
Review system & application logs
Troubleshooting Step 2
Word: Guess
Establish a theory of probable cause (question the obvious):
If necessary, conduct external/internal research based on symptoms
Troubleshooting Step 3
Word: Test
Test the theory to determine the cause:
Once the theory is confirmed, determine the next steps to resolve problem
If theory is not confirmed, re-establish new theory or escalate
Troubleshooting Step 4
Word: Plan/Implement
Establish a plan of action to resolve the problem & implement the solution
Troubleshooting Step 5
Word: Verify
Verify full system functionality and, if applicable, implement preventative measures
Troubleshooting Step 6
Word: Document
Document findings, actions, & outcomes
Port 21
FTP (File Transfer Protocol)
Standard network protocol for transfer of computer files from a server to a client on a network. (Unencrypted)
Port 22
SSH (Secure Shell)
Cryptographic network protocol for operating network services securely over an unsecured network.
Remote CLI, Remote login
Port 23
Telnet
Application protocol used on LAN or Internet to provide a bi-directional interactive text-oriented communication facility using a virtual terminal connection.
Port 25
SMTP (Simple Mail Transfer Protocol)
Industry standard protocol for email sending.
Sends/relays/forwards messages from a mail client to a receiving email server.
Port 53
DNS (Domain Name System)
Naming system for computers, services, or other resources connected to the Internet or a private network.
Port 80
HTTP (Hypertext Transfer Protocol)
Application layer protocol for distributed, collaborative, hypermedia info systems.
Port 110
POP3 (Post Office Protocol 3)
Email protocol that deals with managing & retrieving emails from the receiving server.
Download the email from a server to a single computer, then deletes email from server.
Port 143
IMAP (Internet Message Access Protocol)
Email protocol that deals with managing & retrieving emails from the receiving server.
Stores the message on a server & synchronizes the message across multiple devices.
Port 443
HTTPS (Hypertext Transfer Protocol Secure)
Extension of HTTP used for secure communication. incorporates SSL/TLS
Port 3389
RDP (Remote Desktop Protocol)
Proprietary protocol (Microsoft) that provides user with GUI to connect to another computer over a network connection.
Port 137-139
NetBIOS/NetBT
Networking protocol that allows legacy computer applications relying on the NetBIOS API to be used on modern TCP/IP networks.
Port 445
SMB/CIFS
SMB = Server Message Block
File sharing protocol (IBM) designed to allow computers to read/write files to a remote host over a LAN. Directories made in SMB are called “shares”
CIFS = Common Internet File System
A dialect of SMB (a particular implementation) made by Microsoft
Port 427
SLP (Service Location Protocol)
Service directory protocol that allows computers & other devices to find services in a LAN without prior configuration
Port 548
AFP (Apple File Protocol)
Dynamic file-exchange platform for secure transfer of files within & between organizations.
Port 67/68
DHCP (Dynamic Host Control Protocol)
Network management protocol used to automatically assign IP addresses to devices.
Port 389
LDAP (Lightweight Directory Access Protocol)
Open source industry standard application protocol for accessing/maintaining distributed directory information services over an IP network.
Port 161/162
SNMP (Simple Network Management Protocol)
Internet standard protocol for collecting/organizing info about managed devices on IP networks and for modifying that information to change device behavior.
RAID 0
AKA: Disk Striping
Does not provide redundancy.
Requires at least 2 drives.
One drive fails = all data lost
RAID 1
AKA: Disk Mirroring/Duplexing
Requires at least 2 drives.
Great for safety (more fault-tolerant)
Loss of storage space (duplicated data)
RAID 5
AKA: Disk Striping with Distributed Parity
Requires at least 3 drives.
Fastest way to provide data redundancy.
Uses one drive’s worth of space for parity
Out of favor today.
RAID 10 (1+0)
AKA: Nested Striped Mirrors
Requires at least 4 drives.
Can lose up to 2 drives.
Pair of RAID 1 arrays | Arrays look like single drives
Block stripe across the two mirrored pairs (RAID 0)
802.11a
5GHz 150ft Range 54Mbps 8 channels Less prone to interference than 802.11b & g
802.11b
2.4GHz 300ft Range 11Mbps 14 channels (11 for US) 3 non-overlapping channels
802.11g
2.4GHz 300ft Range 54Mbps 14 channels (11 US) Backwards compatibility: 802.11b Improved security 3 non-overlapping channels
802.11n
2.4 & 5GHz 300ft Range 100+Mbps MIMO (range/speed increase) Backwards compatibility: 802.11b & g Same as 802.11g but with 5GHz band
802.11ac
5GHz 300+ft Range 1Gbps MU-MIMO Backward compatibility: b, g, n
Ipconfig Commands
ipconfig ipconfig /all ipconfig /release ipconfig /renew ipconfig /flushdns
Private IP Addresses
Class A: 10.0.0.0 to 10.255.255.255
Class B: 172.16.0.0 to 172.31.255.255
Class C: 192.168.0.0 to 192.168.255.255
Cloud: On-Demand
Adding/reducing capacity based on demand
The application adjusts according to demands
Cloud: Measured Service
Charges based on traffic going in/out of a web app
Paying for the time that every one of the virtualized services is running
Cloud: Metered Service
Charges based on amount of processing resources used
Enables careful monetization of resources used
Cloud: Resource Pooling
Consolidating a system’s physical & time resources
Cloud: Rapid Elasticity
Being able to easily/quickly expand/contract necessary resources needed
Wireless Encryption
WEP: IV (Initialization Vector) WPA = PSK (Pre-Shared Key) WPA2 = AES (Advanced Encryption System) WPA/WPA2 = TKIP (Temporal Key Integrity Protocol) Highest Level = WPA2-PSK Guest Network = Disable/Open
