Fortinet NSE7_NST-7.2 Practice Test - Questions Answers, Page 4

Session Creation: The output shows an expected session, likely due to a pinhole, which is a dynamically created rule to allow specific traffic through the firewall.

Routing Decision:

The original direction of traffic comes from the IP address 10.171.121.38.

The next-hop IP address for this traffic is 10.0.1.10 as indicated by the routing decision in the output.

Pinhole Session: Pinhole sessions are typically created for protocols that require additional sessions (e.g., FTP, SIP) to function properly. This ensures the necessary traffic can pass through the firewall.

Debugging Commands: The diagnose sys session list command is used to list session information, which helps in understanding traffic flow and troubleshooting connectivity issues.

Fortinet Network Security Support Engineer Study Guide for FortiOS 7.2 (ebin.pub).

General IPsec VPN configuration from Fortinet documentation (Fortinet Docs).

Soft Reset of BGP:

Performing a soft reset of BGP is a common method to resolve issues where prefixes are not being received. It forces both BGP peers to resend their complete routing tables to each other.

This can be done using the command: execute router clear bgp soft in and execute router clear bgp soft out.

Network Import Check:

The network-import-check command controls whether the FortiGate should verify that the prefix exists in the routing table before advertising it.

Disabling this check can resolve issues where valid prefixes are not advertised due to stringent verification.

The command to disable this is: config router bgp set network-import-check disable end.

BGP Configuration Verification:

Ensure that the BGP configuration on FGT-B is correctly set to advertise the network 172.16.54.0/24.

Verify that the network statement is correctly configured and matches the intended prefix.

Fortinet Community: Technical Note on Configuring BGP (Welcome to the Fortinet Community!).

Fortinet Documentation: Configuring BGP on FortiGate (Fortinet Document Library).

Diagnose NPU NP6 Port-list Disable Command:

The diagnose npu np6 port-list disable command disables specific ports on the NP6 processor. This can help in cases where you need to analyze traffic and the hardware offloading is interfering.

Command: diagnose npu np6 port-list disable 5 17 (as shown in Option A).

Diagnose NPU NP6 Fastpath Disable Command:

Disabling the fastpath feature on NP6 can also allow for better visibility into the traffic as it bypasses hardware acceleration, which might obscure traffic details.

Command: diagnose npu np6 fastpath disable 0 (as shown in Option C).

Fortinet Documentation on Troubleshooting BGP and NPU Settings (Fortinet Docs).

Fortinet Community Technical Notes on NPU and Traffic Analysis (Welcome to the Fortinet Community!).

Conserve Mode Overview: Conserve mode is a state that FortiGate enters to protect itself from running out of memory. It is triggered when the memory usage reaches certain thresholds.

Thresholds: The default settings for conserve mode thresholds are:

Red Threshold: 88% memory usage.

Extreme Threshold: 95% memory usage.

Green Threshold: 82% memory usage.

Impact on Sessions: When in conserve mode:

New sessions requiring flow-based content inspection are blocked.

New sessions requiring proxy-based content inspection are also blocked to free up memory resources.

Current Memory State in Exhibit: The exhibit shows:

Total RAM: 3040 MB.

Memory used: 2706 MB (89% of total RAM).

Memory usage exceeds the red threshold (88%), thus triggering conserve mode.

Given that the memory usage is above the red threshold and conserve mode is active, the FortiGate will block new sessions requiring both flow-based and proxy-based content inspection to conserve memory.

Fortinet Community: Explanation of Conserve Mode and Its Impact (Welcome to the Fortinet Community!) (Welcome to the Fortinet Community!).

Fortinet Documentation: Conserve Mode Settings and Management (Fortinet Docs).

Analyzing Debug Output:

The debug output shows multiple proposals with encryption algorithms like AES CBC and hashing algorithms like SHA256.

The negotiation failure (no SA proposal chosen) suggests that there is a mismatch in the encryption or hashing algorithms between the local and remote gateways.

Configuration Change:

To resolve the phase 1 negotiation error, the local gateway needs to include a compatible proposal.

Adding AES256-SHA256 to the phase 1 proposal configuration ensures that both gateways have a matching set of encryption and hashing algorithms.

Fortinet Documentation: Configuring IPsec Tunnels (Fortinet Docs) (Welcome to the Fortinet Community!).

Fortinet Community: Troubleshooting IKE Negotiation Failures (Welcome to the Fortinet Community!) (Welcome to the Fortinet Community!).

Statistics and Configuration Information:

Application-layer test commands can display detailed statistics and configuration information about specific features or processes. For example, commands like diagnose vpn ipsec tunnel list provide detailed statistics about VPN tunnels.

Real-time Debugs:

These commands also facilitate real-time debugging of applications and processes. For instance, using diagnose debug application followed by the specific application, such as fssod, provides real-time debug information which is crucial for troubleshooting.

Fortinet Community: Useful FSSO Commands and Troubleshooting (Welcome to the Fortinet Community!) (Welcome to the Fortinet Community!).

Fortinet Documentation: Application-layer Test Commands (Fortinet GURU).

IKE_SA_INIT Exchange:

The IKE_SA_INIT exchange is the first step in the IKEv2 negotiation process. It is responsible for setting up the initial security association (SA) and performing Diffie-Hellman key exchange.

During this exchange, the responder may employ various measures to protect against Denial of Service (DoS) attacks, such as rate limiting and the use of puzzles to increase the computational cost for an attacker.

DoS Protection Mechanisms:

One key method involves limiting the number of half-open SAs from any single IP address or subnet.

The IKE_SA_INIT exchange can also incorporate the use of stateless cookies, which help to verify the initiator's legitimacy without requiring extensive resource allocation by the responder until the initiator is verified.

RFC 5996: Internet Key Exchange Protocol Version 2 (IKEv2) (RFC Editor).

RFC 8019: Protecting Internet Key Exchange Protocol Version 2 (IKEv2) Implementations from Distributed Denial-of-Service Attacks (IETF Datatracker).

Capturing ESP Traffic:

ESP (Encapsulating Security Payload) traffic is associated with IPsec and is identified by the protocol number 50. To capture ESP traffic, you need to filter packets based on this protocol.

In this specific case, you also need to filter for the host associated with the VPN tunnel, which is 10.200.3.2 as indicated in the exhibit.

Sniffer Command:

The correct command to capture ESP traffic for the VPN named DialUp_0 is:

diagnose sniffer packet any 'esp and host 10.200.3.2'

This command ensures that only ESP packets to and from the specified host are captured, providing a focused and relevant data set for troubleshooting.

Fortinet Documentation: Verifying IPsec VPN Tunnels (Fortinet Docs) (Welcome to the Fortinet Community!).

Fortinet Community: Troubleshooting IPsec VPN Tunnels (Welcome to the Fortinet Community!) (Fortinet Docs).

Routing Table Analysis:

The first command output (get router info routing-table database) shows two default routes:

One via port1 with a distance of 10.

One via port2 with a distance of 20.

The second command output (get router info routing-table all) only shows the route via port1.

Administrative Distance:

The administrative distance (AD) is a measure used by routers to select the best path when there are multiple routes to the same destination. The lower the distance, the more preferred the route.

In this scenario, the route via port1 has a lower distance (10) compared to the route via port2 (20), making it the preferred route.

Route Selection:

Since the route via port1 has a lower distance, it is the only one installed in the active routing table, which is why it appears in the second command output, and the port2 route does not.

Fortinet Community: Routing behavior depending on distance and priority (Welcome to the Fortinet Community!) (Welcome to the Fortinet Community!).

Fortinet GURU: Route priority and administrative distance explanations (Fortinet GURU).