3Com REMOTE ACCESS SYSTEM 1500, Management Manual

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218 C
HAPTER
14: H
ANDLING
P
ACKET
F
ILTERS
Filtering Overview
Packet filters are used primarily in networks that cross organizational or
corporate boundaries. They control inter-network data transmission by
accepting or rejecting the passage of specific packets through network
interfaces based on packet header information.
When data packets are received by a network interface such as a modem,
a packet filter analyzes packet header data against its set of rules. Based
on rules that you define, the filter permits the packet to pass through or
discards it.
Filtering Capabilities The RAS 1500 supports the following filtering capabilities:
■
Input/output filtering — Packet filters can be used to control inbound
or outbound data packets.
■
Source/destination address filtering — A packet filter can accept or
deny access to a host or user based on the address of the source
and/or destination.
■
Protocol filtering — Inbound or outbound network traffic can be
evaluated based on the protocol.
■
Source/destination port filtering — A packet filter can control what
services local or remote users can access.
■
Call filtering can control whether a packet can initiate an outgoing
call.
■
Controls the content of IP Routing Information Protocol (RIP) packets
sent or received on specific ports.
■
Remote Authentication Dial-In User Service (RADIUS) and
filtering. See Chapter 12, “Using Security and Accounting” for more
information.