Common Ports Flashcards
SSH - Secure Shell
- Encrypted communication link - tcp/22
* Looks and acts the same as Telnet
DNS - Domain Name System
- Converts names to IP addresses - udp/53
- www.professormesser.com = 162.159.246.164
- These are very critical resources
- Usually multiple DNS servers are in production
SMTP - Simple Mail Transfer Protocol
- SMTP - Simple Mail Transfer Protocol
- Server to server email transfer - tcp/25
• Also used to send mail from a device to a mail server
• Commonly configured on mobile devices
and email clients
- Other protocols are used for clients to receive email
- IMAP, POP3
SFTP - Secure FTP
• Uses the SSH File Transfer Protocol - tcp/22
• Provides file system functionality
• Resuming interrupted transfers, directory listings,
remote file removal
File Transfer Protocols
- FTP – File Transfer Protocol
- tcp/20 (active mode data), tcp/21 (control)
- Transfers files between systems
- Authenticates with a username and password
- Full-featured functionality (list, add, delete, etc.)
- TFTP – Trivial File Transfer Protocol
- udp/69
- Very simple file transfer application
- Read files and write files
- No authentication - Not used on production systems
Telnet
- Telnet – Telecommunication Network - tcp/23
- Login to devices remotely
- Console access
- In-the-clear communication
- Not the best choice for production systems
DHCP - Dynamic Host Configuration Protocol
• Automated configuration of IP address,
subnet mask and other options
• udp/67, udp/68 - Requires a DHCP server
- Dynamic / pooled
- IP addresses are assigned in real-time from a pool
- Each system is given a lease
- Must renew at set intervals
- Reserved
- Addresses are assigned by MAC address
- Quickly manage addresses from one location
SNMP - Simple Network Management Protocol
- Gather statistics from network devices
- udp/161
- v1 – The original
- Structured tables, in-the-clear
- v2 – A good step ahead
- Data type enhancements, bulk transfers
- Still in-the-clear
- v3 – The new standard
- Message integrity, authentication, encryption
RDP - Remote Desktop Protocol
• Share a desktop from a remote location over
tcp/3389
• Remote Desktop Services on many Windows versions
• Can connect to an entire desktop or just an
application
• Clients for Windows, MacOS, Linux, iPhone, and
others
NTP - Network Time Protocol
- Switches, routers, firewalls, servers, workstations
- Every device has its own clock - udp/123
- Synchronizing the clocks becomes critical
- Log files, authentication information, outage details
- Automatic updates
- No flashing 12:00 lights
• Flexible - You control how clocks are updated
- Very accurate
- Accuracy is better than 1 millisecond
SIP - Session Initiation Protocol
- Voice over IP (VoIP) signaling
- tcp/5060 and tcp/5061
- Setup and manage VoIP sessions
- Call, ring, hang up
• Extend voice communication
• Video conferencing, instant messaging, file transfer,
etc
SMB - Server Message Block
- Protocol used by Microsoft Windows
- File sharing, printer sharing
- Also called CIFS (Common Internet File System)
• Direct over tcp/445 (NetBIOS-less)
• Direct SMB communication over TCP
without the NetBIOS transport
POP/IMAP
- Receive emails from an email server
- Authenticate and transfer
- POP3 - Post office Protocol version 3 - tcp/110
- Basic mail transfer functionality
• IMAP4 - Internet Message Access Protocol v4
tcp/143
• Manage email inbox from multiple clients
LDAP/LDAPS
• LDAP (Lightweight Directory Access Protocol) -
tcp/389
• Store and retrieve information in a network directory
- LDAPS (LDAP Secure) - tcp/636
- A non-standard implementation of LDAP over SSL
H.323
- Voice over IP (VoIP) signaling - tcp/1720
- ITU Telecommunication H.32x protocol series
- Setup and manage VoIP sessions
- Call, ring, hang up
- One of the earliest VoIP standards
- Still in use today
