Avaya Configuring Traffic Filters and Protocol Prioritization Manuel d'utilisateur télécharger pdf (Page 174)

Configuring Traffic Filters and Protocol Prioritization

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Using a Drop-All Filter As a Firewall

If your filtering strategy involves forwarding most traffic and dropping only

specified packets, you need only configure filters with a drop action (Drop filters)

for the traffic you want the router to reject.

If your strategy involves blocking most traffic and accepting only specified

packets, begin by defining filters to accept specified packets (Accept filters). Then,

add a filter on the interface to drop all packets (a Drop-all filter).

A Drop-all filter describes the broadest range of packets you want to block from

an interface. To ensure that all unwanted traffic is dropped, configure the Drop-all

filter to contain:

• Criteria that appears in every packet of the protocol you want to filter

• The maximum value of the range

• The minimum value of the range

With a Drop-all filter, higher-precedence Accept filters create exceptions (or

“holes”) in the drop-all range. Since the highest-precedence filter in a given

address range determines the result of combined filtering within that range, the

router will process packets that match the Accept filters. However, the Drop-all

filter ensures that the router rejects all other traffic.

For example, to configure a circuit that only accepts IP traffic addressed for

destination address 192.32.28.55, apply a Drop-all filter and one Accept filter, as

follows:

See “Changing Inbound Traffic Filter Precedence” on page 6-18” (inbound traffic

filters) or “Changing Outbound Traffic Filter Precedence” on page 7-21 (outbound

traffic filters) for information about using the Configuration Manager to change

filter precedence after filters have been applied to an interface.

Filter Action Rule Number Start of Range End of Range

Accept 1 (highest precedence) 192.32.28.55 192.32.28.55

Drop 2 (lower precedence) 0.0.0.0.0 255.255.255.255

1 2 ... 169 170 171 172 173 174 175 176 177 178 179 ... 183 184

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Avaya Configuring Traffic Filters and Protocol Prioritization Manuel d'utilisateur Page 174