6V0-21.25 practice question 10 of 10

Which statements are true for DFW and Rule processing order based on the information shown in the image? (Select all that apply)…

Which statements are true for DFW and Rule processing order based on the information shown in the image? (Select all that apply) [root@vesxi-nsxt-10:~] vsipioctl getconfig -f nic-2292571-ethO-vmware-sfw.2 ruleset mains { # generation number: 0 # realization time : 2020-05-21T13:01:48 # FILTER rules rule 1596 at 1 inout protocol tcp from addrset e70a9a79-c346-48c4-8b9d- 402e97e38a7c to addrset be665396-14d9-4ee4-98b9- 9c21ebfl27a port 464 accept; rule 1596 at 2 inout protocol udp from addrset e70a9a79-c346-48c4-8b9d- 402e97e38a7c to addrset be665396-14d9-4ee4-98b9- 9c21ebfl27a port 464 accept; rule 1595 at 3 inout protocol udp from addrset e70a9a79-c346-48c4-8b9d- 402e97e38a7c to addrset 9edl2e5f-36f4-42a9-a79b- 87efc243alef port 53 accept; rule 1594 at 4 inout protocol udp from addrset e70a9a79-c346-48c4-8b9d- 402e97e38a7c to addrset 59e6aa90-e360-4341-9fb3- b312772b79fb port 123 accept; rule 2 at 5 inout protocol any from any to any accept; }

Answer options

A: Rule 1595 will be processed before rule 1596

B: Rule 1594 will be processed after 1595 and 1596 Correct answer

C: Rule 1596 will be the first one to be processed Correct answer

D: Rule 2 will only be processed if the conditions for the above rules are not met Correct answer

Correct Answer:

B. Rule 1594 will be processed after 1595 and 1596; C. Rule 1596 will be the first one to be processed; D. Rule 2 will only be processed if the conditions for the above rules are not met

Explanation

The vsipioctl getconfig command displays the firewall ruleset as applied on the ESXi host's data plane. The processing order is determined by the position number indicated by at X in the output, not the rule ID.
- Rule 1596 is at position 1, making it the first rule to be evaluated.
- Rule 1594 is at position 4, which is processed after rules at positions 1, 2 (1596), and 3 (1595).
- The Distributed Firewall (DFW) operates on a first-match basis. A packet is evaluated sequentially against the rules. If it does not match any of the rules from positions 1 through 4, it will then be evaluated against Rule 2 at position 5.

Why Incorrect

A. Rule 1595 is at position 3, while Rule 1596 is at positions 1 and 2. Rules with lower position numbers are always processed first.

References

1. VMware NSX Data Center Administration Guide: In the "Distributed Firewall" section, it is stated that "Rules in a policy section are enforced from top to bottom. The first rule in the top-most section that matches the traffic parameters is enforced." This confirms the sequential, first-match processing logic.

2. VMware NSX Data Center Troubleshooting Guide: The section "Troubleshoot Distributed Firewall using the vsipioctl Command" explains how to use vsipioctl to inspect the realized firewall rules on a host. The output format, including rule at , directly shows the data plane processing order, where dictates the sequence.

3. VMware Knowledge Base Article 83836, "Troubleshooting Distributed Firewall (DFW) on NSX-T": This document details the use of vsipioctl getrules and vsipioctl getconfig. It confirms that the output reflects the exact order of rule evaluation in the data path, with the position number being the definitive factor for processing sequence.

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