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Security 13-7
Port number comparisons
A filter can also use a comparison option to evaluate a packet’s source or destination port number. The
comparison options are:
No Compare: No comparison of the port number specified in the filter with the packet’s port number.
Not Equal To: For the filter to match, the packet’s port number cannot equal the port number specified in the
filter.
Less Than: For the filter to match, the packet’s port number must be less than the port number specified in the
filter.
Less Than or Equal: For the filter to match, the packet’s port number must be less than or equal to the port
number specified in the filter.
Equal: For the filter to match, the packet’s port number must equal the port number specified in the filter.
Greater Than: For the filter to match, the packet’s port number must be greater than the port number specified
in the filter.
Greater Than or Equal: For the filter to match, the packet’s port number must be greater than or equal to the
port number specified in the filter.
Internet service TCP port Internet service TCP port
FTP 20/21 Finger 79
Telnet 23 World Wide Web 80
SMTP (mail) 25 News 144
Gopher 70 rlogin 513
Internet service UDP port Internet service UDP port
Who Is 43 AppleTalk Routing
Maintenance (at-rtmp)
202
World Wide Web 80 AppleTalk Name Binding
(at-nbp)
202
SNMP 161 AURP (AppleTalk) 387
TFTP 69 who 513