Table 6-5 shows an abbreviated list of some well-known port numbers of the various
TCP applications.
http://www.iani.org/assignments/port-numbers provides a more comprehensive list of well-known port numbers.
To con?¬?gure numbered extended IPv4 ACLs on a Cisco router, create an extended IPv4 ACL and
activate that ACL on an interface. Use the access-list command to create an entry to express a
condition statement in a complex ?¬?lter. The full command follows:
aacccceessss--lliisstt access-list-number {ppeerrmmiitt | ddeennyy}
protocol source source-wildcard [ operator port]
destination destination-wildcard [ operator port]
[eessttaabblliisshheedd] [lloogg]
Table 6-5 Well-Known Port Numbers and IP Protocols
Well-Known Port Number (Decimal) IP Protocol
20 (TCP) FTP data
21 (TCP) FTP control
23 (TCP) Telnet
25 (TCP) Simple Mail Transfer Protocol (SMTP)
53 (TCP/UDP) Domain Name System (DNS)
69 (UDP) TFTP
80 (TCP) HTTP
Source
Address
Destination
Address
Protocol
Port
Number
Permit Deny
Frame
Header
(for Example,
HDLC)
Packet
(IP Header)
An Example from a TCP/IP Packet
Segment
(for Example,
TCP Header)
Data
Use ACL
Statements
100??“199 or
2000??“2699
to Test the
Packet
Con?¬?guring ACLs 229
Table 6-6 explains the syntax of the command.
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