USRobotics NETServer/8 - Manual (Page 115)

Packet Filters 8-1
Chapter 8
Packet Filters
This chapter covers setting up packet filters for the NETServer.
The following topics are included:
•
Filter overview
•
Creating new packet filters
•
Filter rule format
•
TCP/IP packet filtering
•
IPX packet filtering
•
Editing Packet filters
Packet Filters
Packet filters are primarily used in networks that cross organiza-
tional or corporate boundaries. They control inter-network data
transmission by permitting or denying the passage of specific
packets through network interfaces.
When data packets are received by a network interface such as a
modem, the packet filter analyzes their header information.
After evaluating the data packet against its set of rules, the filter
permits it to pass through or discards it. If an IP packet is
discarded, the NETServer sends an ICMP “Host Unreachable”
message back to the originator.