JNCIA Changed JN0-105 Questions

The Packet Forwarding Engine (PFE) in Junos OS performs several key functions, including implementing firewall filters (A) and forwarding transit traffic (C). The PFE applies firewall filter rules to incoming and outgoing traffic and is responsible for the high-speed forwarding of packets based on the information in the forwarding table.

At the operational mode prompt on a Junos device, you can use various commands to view the device's status and request system operations. The show interface ge-0/0/0 command is used to display information about a specific interface, while the request system shutdown command is used to properly shut down the device. The set command is used in configuration mode, not operational mode, and the run command is used to execute operational mode commands from configuration mode.

Firewall filters in Junos OS are stateless, meaning they process each packet individually without regard to the state of a connection or sequence of packets. These filters can match various packet attributes, including those at Layer 4, such as TCP and UDP port numbers. This allows for granular control over traffic based on the type of service or application. Unlike stateless filters, stateful firewalls keep track of the state of active connections and make decisions based on the context of the traffic flow, which is not a capability of Junos firewall filters. Additionally, Junos firewall filters primarily operate up to Layer 4 and do not natively inspect Layer 7 parameters, which involve application-level data.

In Juniper firewall filter configurations, "discard" and "accept" are two valid terminating actions for a term within a filter. The "discard" action drops the packet, preventing it from reaching its intended destination, while the "accept" action allows the packet to pass through the filter, proceeding to its next hop or destination. "Count" is a non-terminating action that increments a counter every time a packet matches the term but does not inherently determine the packet's fate. "Next term" directs the evaluation to proceed to the next term in the filter for further processing, also a non-terminating action.