Networks V

Categories of Ports



You should become familiar with the various categories used to
organize IP ports. Port numbers can range from 0 to 65536. The way
these ports are used is regulated by the Internet Corporation for
Assigned Names and Numbers (ICANN). IP ports are lumped into three
different categories:





Well-known ports 

Reserved for specific services, well-known ports
are those numbered from 0 to 1023. Here are some examples:


• Ports 20 and 21: FTP

• Port 22: Secure Shell (SSH)

• Port 23: Telnet

• Port 25: SMTP

• Port 53: DNS

• Port 80: HTTP

• Port 110: POP3

• Port 119: NNTP (news)

• Port 123: NTP (time synchronization)

• Ports 137, 138, 139: NetBIOS

• Port 143: IMAP

• Port 161: SNMP

• Port 162: SNMP Traps

• Port 389: LDAP

• Port 443: HTTPS

• Port 465: SMTP using TLS/SSL (SMTPS)

• Port 514: Syslog remote logging

• Port 636: Secure LDAP

• Port 993: IMAP using TLS/SSL (IMAPS)

• Port 995: POP3 using TLS/SSL (POP3S)





Registered ports 

ICANN has reserved ports 1024 through 49151 for
special implementations. Organizations can create their own network
service and then apply for a registered port number to be assigned to
it.





Dynamic ports 

Dynamic ports are also called private ports. Ports
49152 through 65535 are designated as dynamic ports. They are
available for use by any network service. They are frequently used by
network services that need to establish a temporary connection. For
example, the service may negotiate a dynamic port with the client. It
will then use that port during the session. When the session is
complete, the port is closed.




To make all of this work, you need to assign each host on the network
an IP address.











LX0-104 Exam Objectives (R)