Netopia 4541 User Reference Manual page 151

Parts of a filter
A filter consists of criteria based on packet attributes. A typical filter can match a packet on any one of the
following attributes:
The source IP address (where the packet was sent from)
The destination IP address (where the packet is going)
The type of higher-layer Internet protocol the packet is carrying, such as TCP or UDP
Port numbers
A filter can also match a packet's port number attributes, but only if the filter's protocol type is set to TCP or
UDP, since only those protocols use port numbers. The filter can be configured to match the following:
The source port number (the port on the sending host that originated the packet)
The destination port number (the port on the receiving host that the packet is destined for)
By matching on a port number, a filter can be applied to selected TCP or UDP services, such as Telnet, FTP, and
World Wide Web. The following tables show a few common services and their associated port numbers:
Internet service
FTP
Telnet
SMTP (mail)
Gopher
Internet service
Who Is
World Wide Web
SNMP
TFTP
TCP port Internet service
20/21 Finger
23 World Wide Web
25 News
70 rlogin
UDP port Internet service
43 AppleTalk Routing
Maintenance (at-rtmp)
80 AppleTalk Name Binding
(at-nbp)
161 AURP (AppleTalk)
69 who
Security 11-7
TCP port
79
80
144
513
UDP port
202
202
387
513