3Com REMOTE ACCESS SYSTEM 1500, Management Manual

Page: 221 / 300

Filter Types
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Filter Types
Filters can be classified by the following types:
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Data filters — based on protocol-specific packet information
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Advertisement filters — based on broadcast packet information
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Generic filters — based on packet structure
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Call filters — based on outgoing calls
Data Filters Data filters control network access based on protocol, source/destination
address, and source/destination port designation (for example,
Transmission Control Protocol [TCP]/User Datagram Protocol [UDP] port
designations) of the packet.
The RAS 1500 supports Internet Protocol (IP) and Internetwork Packet
Exchange (IPX)-related filters. This filter type controls network access
based on the protocol and source/destination address. IP filter rules allow
filtering on source address, destination address, protocol type, source
port, and destination port of the IP packet. IPX filter rules allow filtering
on source network, destination network, protocol type, source socket,
destination socket, source node, and destination node of the IPX packet.
Advertisement Filters Advertisement filters act on network protocol packets that contain
information such as Routing Information Protocol (RIP). Filtering these
packets is performed by the specific protocol process.
IP-RIP, IPX-RIP, and IPX-Service Advertising Protocol (SAP) are supported by
the RAS 1500. The IP-RIP filter type controls the content of IP RIP packets
that are sent out or received. The IP- and IPX-RIP filtering process filters
addresses from the RIP packet upon transmission (output filter) and does
not enter routes into the Routing Table upon receipt (input filter).
The IPX-SAP filter type controls the content of SAP packets that are
transmitted or received. The IPX-SAP filter rules allow filtering on service
type, server name, network address, node address, and the socket
number fields of the service entry. The forwarding process uses the filter
information to prevent service data from being included in the SAP
packet.