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Routing & Switching · Intermediate

Firewall Filter

A Junos stateless packet filter, like an ACL, whose terms match packets (from) and apply actions such as accept, discard, count or policer.

Definition

Firewall filters are applied to logical interfaces in the input or output direction per family (inet, inet6, ethernet-switching). A term without a from clause matches all packets. There is an implicit discard at the end of each filter. Filters on lo0 protect the Routing Engine.

Example

set firewall family inet filter PROTECT-RE term SSH from protocol tcp destination-port ssh ; then accept

Exam tip

Junos discard drops silently; reject sends ICMP unreachable.

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