What is the default action for firewall filters?

The correct answer is C. discard. The default action for firewall filters in Junos OS is to implicitly discard a packet if it does not match any configured term or if a matched term lacks an explicit action.

Routing Policy and Firewall Filters

Question

Options

Aaccept
Breject
Cdiscard
Dlog

How the community answered

(31 responses)

A
6% (2)
B
3% (1)
C
87% (27)
D
3% (1)

Why each option

The default action for firewall filters in Junos OS is to implicitly discard a packet if it does not match any configured term or if a matched term lacks an explicit action.

Aaccept

`accept` is an explicit action to allow a packet to pass, not the default action.

Breject

`reject` is an explicit action that drops the packet and sends an ICMP unreachable message back to the sender, which is not the silent default.

CdiscardCorrect

When a packet does not match any term in a firewall filter, or if a term is matched but no `then` action is explicitly specified, the Junos OS firewall filter implicitly performs a `discard` action. This means the packet is silently dropped without sending any notification.

Dlog

`log` is an action to record information about the matched packet in a system log file, which is not a terminating action or the default.

Concept tested: Junos firewall filter default action

Source: https://www.juniper.net/documentation/us/en/software/junos/routing-policy/topics/topic-map/firewall-filter-config-terms-overview.html

Topics

#firewall filters#default action#discard#implicit deny

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