Enterasys Networks CSX7000 Manual do Utilizador descarregar pdf (Página 302)

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USER’S GUIDE

302 CyberSWITCH

Sample packet passing through a filter

ILTER COMPOSITION

The IP filtering mechanism is composed of three fundamental building blocks:

• Packet Types

The criteria for describing an IP datagram’s contents: IP Source and Destination Addresses,

Protocol (TCP, UDP, etc.), Protocol-specific fields (TCP port, etc.). For example, Packet Types

can be set up to specify such things as: “all packets arriving from IP Subnetwork X”, “Telnet

packets destined for host Y”, or “All RIP packets”. Packet Types are independently defined and

may be referenced by multiple filters.

• Conditions

A Packet Type combined with an Action to take when a datagram matches that type. The

Actions are DISCARD or FORWARD.

• Filter

An ordered list of Conditions. When an IP datagram passes through a filter, a sequential pass

is made through the individual conditions. The first complete match of a Packet Type dictates

the action which is applied to the datagram. When the action is DISCARD, the datagram is

dropped. The filter also contains a configurable Final Condition which specifies the action to

take if no match is found.

YPES OF FILTERS

Forwarding Filters

A Forwarding Filter is a filter which forwards or discards specific packets according to whether

these packets fulfill a list of defined conditions.Forwarding Filters may be applied to packets in one

of the following ways:

• Globally: independent of the packet’s input or output path.

•through the Input Network Interface: applies the filter only to packets arriving on a specific

IP Packet

Discard

Type 1

Forward

Type 4

Discard

Type 3

FILTER

Discard

All Other Types

Conditions

Final

Condition

Packet Types:

Type 1: www,www,www

Type 2: xxx,xxx,xxx

Type 3: yyy,yyy

Type 4: zzz,zzz

Action:

Discard/Forward

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