JN0-636 Exam Dumps : Security, Professional (JNCIP-SEC)

To troubleshoot the traffic problem using the match criteria, you need to use the show security match-policies CLI command. The other options are incorrect because:

• A. The show security policy-report CLI command displays the policy report, which is a summary of the policy usage statistics, such as the number of sessions, bytes, and packets that match each policy. It does not show the match criteria or the reason why the traffic is not hitting the policy1.
• B. The show security application-tracking counters CLI command displays the application tracking counters, which are the statistics of the application usage, such as the number of sessions, bytes, and packets that match each application. It does not show the match criteria or the reason why the traffic is not hitting the policy2.
• D. The request security policies check CLI command checks the validity and consistency of the security policies, such as the syntax, the references, and the conflicts. It does not show the match criteria or the reason why the traffic is not hitting the policy3.

Therefore, the correct answer is C. You need to use the show security match-policies CLI command to troubleshoot the traffic problem using the match criteria. The show security match-policies CLI command displays the policies that match the specified criteria, such as the source and destination addresses, the zones, the protocols, and the ports. It also shows the action and the hit count of each matching policy. You can use this command to verify if the traffic is matching the expected policy or not, and if not, what policy is blocking or rejecting the traffic4

Proxy ARP is a technique used by routers to answer ARP requests on one network segment on behalf of hosts on another network segment. This is useful in situations where a host on one network segment needs to communicate with a host on another network segment, but the two hosts are not directly connected. In this case, the router acts as a proxy, answering ARP requests on behalf of the other host. In the exhibit, the vSRX device is configured to use a pool of addresses that are in the same subnet as the external interface ge-0/0/0 for source NAT. This means that the vSRX device will translate the source IP address of the internal hosts to one of the addresses in the pool before sending the packets to the external network. However, the external hosts will not know how to reach the NATed addresses, since they are not directly connected to the vSRX device. They will send ARP requests for the NATed addresses, expecting to receive a MAC address from the vSRX device. If proxy ARP is not enabled on the vSRX device, it will not respond to these ARP requests, since it does not have the NATed addresses configured on its interface. The ARP requests will time out and the packets will be dropped by the external hosts or the service provider router. To solve this problem, proxy ARP must be enabled on the vSRX device for the NATed addresses. This will allow the vSRX device to respond to the ARP requests from the external hosts, providing its own MAC address as the destination. The external hosts will then send the packets to the vSRX device, which will reverse the NAT and forward the packets to the internal hosts. References:

• Configuring Proxy ARP (CLI Procedure)
• [SRX] When and how to configure Proxy ARP (https://supportportal.juniper.net/s/article/SRX-Dynamic-VPN-scenario-for-configuring-Proxy-ARP-on-SRX?language=en_US)

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