Netopia 4542 用户手册

FTP sessions. To allow WAN-originated FTP sessions to a LAN-based FTP ser ver with the IP address a.b.c.d 
(corresponding to a numbered IP address such as 163.176.8.243), inser t the following input filter ahead of the 
current input filter 1:

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Enabled: Yes

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For ward: Yes

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Source IP Address: 0.0.0.0

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Source IP Address Mask: 0.0.0.0

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Dest. IP Address: a.b.c.d

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Dest. IP Address Mask: 255.255.255.255

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Protocol Type: TCP

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Source Por t Comparison: No Compare

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Source Por t ID: 0

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Dest. Por t Comparison: Equal

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Dest. Por t ID: 21

Note: A similar filter could be used to permit Telnet or WWW access. Set the Dest. Por t ID to 23 for Telnet or to 
80 for WWW.

Note: Deleting a filter set does not delete the filters in that set. However, the filters in the deleted set are no 
longer in effect (unless they are par t of another set). The deleted set will no longer appear in the answer profile 
or any connection profiles to which it was added.

Filter rule: A filter set is comprised of individual filter rules.

Filter set: A grouping of individual filter rules.

Firewall: A component or set of components that restrict access between a protected network and the Internet, 
or between two networks.

Host: A workstation on the network.

Packet: Unit of communication on the Internet.

Packet filter: Packet filters allow or deny packets based on source or destination IP addresses, TCP or UDP 
por ts, or the TCP ACK bit.

Port: A number that defines a par ticular type of ser vice.