JN0-637 Exam Dumps - Security, Professional (JNCIP-SEC)

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Persistent NAT with target host allows external hosts to establish connections only when the internal device initiates a session first, ideal for specific interactive applications. Refer to Juniper Persistent NAT Documentation.

The scenario requires that external hosts be able to initiate a connection only if the internal device has already initiated a connection. The correct solution is Persistent NAT with target host, which ensures that a specific external host can initiate new connections back to the internal device, but only after the internal device has established a session first.

Persistent NAT with Target Host (Answer C): This allows the internal device to initiate a connection, and once established, the specified external host can also initiate new connections to the internal device on the same NAT mapping.

Example Configuration:

bash

set security nat source persistent-nat permit target-host-port

This solution is appropriate when controlled bidirectional communication is required based on an internal-initiated connection.

Comprehensive Detailed Step-by-Step Explanation with All Juniper Security References

Understanding NAT64:

NAT64 allows IPv6-only clients to communicate with IPv4 servers by translating IPv6 addresses to IPv4 addresses and vice versa.

It is essential in environments where IPv6 clients need access to IPv4 resources.

Flow-Based vs. Packet-Based Forwarding Modes:

Flow-Based Forwarding Mode:

The SRX device processes packets based on the session state.

Supports advanced services like NAT, IDP, and ALG.

Packet-Based Forwarding Mode:

The SRX device processes each packet individually without maintaining session state.

Limited support for advanced services.

Option A: An SRX Series device should be in flow-based forwarding mode for IPv4.

True.

NAT64 requires flow-based mode for IPv4 traffic to properly translate and maintain session states.

Option B: An SRX Series device should be in packet-based forwarding mode for IPv4.

False.

Packet-based mode does not support NAT features.

Option C: An SRX Series device should be in packet-based forwarding mode for IPv6.

False.

Similar to IPv4, NAT64 requires flow-based mode for IPv6 traffic.

Option D: An SRX Series device should be in flow-based forwarding mode for IPv6.

True.

Flow-based mode is necessary for NAT64 to handle IPv6 traffic correctly.

Key Points:

NAT64 Requires Flow-Based Mode:

Both IPv4 and IPv6 interfaces involved in NAT64 must be configured in flow-based mode.

This is because NAT64 relies on session information and stateful packet inspection.

Packet-Based Mode Limitations:

Does not support NAT, as it lacks session awareness.

Not suitable for NAT64 operations.

Juniper Security References:

Juniper Networks Documentation:

"NAT64 is supported only in flow-based processing mode."

Source: Configuring NAT64

Understanding Flow-Based and Packet-Based Modes:

"Flow-based mode is required for stateful services such as NAT."

Source: Flow-Based and Packet-Based Processing

Conclusion:

To implement NAT64 on an SRX Series device, both IPv4 and IPv6 traffic must be processed in flow-based forwarding mode.

Therefore, Options A and D are the correct statements.