Question

Difficulty: MediumManaging Networking Resources

An operations team manages a Virtual Private Cloud (VPC) network in Google Cloud. An existing ingress firewall rule named `deny-all-app-ingress` with priority `1000` denies all incoming TCP traffic on port `8080` across all instances in the VPC. The team needs to grant temporary access on TCP port `8080` specifically for management traffic originating from the IP range `10.10.0.0/24`. The administrator creates a new ingress firewall rule named `allow-mgmt-ingress` targeted at the same instances. Which priority configuration must be assigned to `allow-mgmt-ingress` to ensure management traffic is allowed without deleting or modifying `deny-all-app-ingress`?

  1. A priority number less than 1000 (such as 500)Answer
  2. B
    A priority number greater than 1000 (such as 1500)
  3. C
    A priority number equal to 1000
  4. D
    Priority 65535

Answer

Assign a priority number less than 1000 (such as 500) to the new rule so that it is evaluated prior to the existing priority 1000 deny rule.
In Google Cloud VPC networks, firewall rules are evaluated based on priority numbers ranging from 0 to 65535. Lower numerical values have higher evaluation precedence. Assigning a priority number less than 1000 (such as 500) guarantees that incoming traffic from 10.10.0.0/24 on port 8080 will match the allow rule first and be permitted before reaching the deny rule set at priority 1000.

Step-by-Step Solution

1
Understand GCP firewall evaluation order
Firewall rule priorities range from 0 to 65535, where 0 has the highest precedence and lower numerical values evaluate before higher ones.
Traffic matching is determined by the first rule evaluated that matches the packet criteria.
2
Compare priority numbers relative to the existing deny rule
The existing rule `deny-all-app-ingress` has priority 1000. To override it for matching source traffic (`10.10.0.0/24`), the new allow rule must have a priority strictly less than 1000 (e.g., 500).
A rule with priority 500 will be matched and applied first, allowing the management traffic before the rule with priority 1000 can deny it.

Key Concept

VPC Firewall Rule Precedence and Priority Evaluation
Estimated Time:1m 30s
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