156-215.81.20 Security Policy and NAT Practice Question
Exhibit
fw ctl get int fw_nat_ignore_dest_if_any fw_nat_ignore_dest_if_any = 0
Refer to the exhibit. An administrator notices that traffic intended for a NAT rule is being dropped because the destination interface is being incorrectly evaluated. Given the current kernel parameter setting, what does this indicate regarding NAT policy processing?
⚠ Common exam trap
Candidates often overlook kernel parameters and assume NAT rules are global. They fail to realize that 'fw_nat_ignore_dest_if_any' dictates whether the destination interface is a mandatory match for NAT.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The gateway must match the destination interface for NAT rules.
The parameter 'fw_nat_ignore_dest_if_any' set to 0 means the security gateway considers the destination interface when matching NAT rules. If the gateway receives traffic on an interface not specified in the NAT rule, it will not perform the translation. Setting this to 1 would ignore the destination interface, which is often used in complex VPN or multi-homed environments to simplify NAT rule matching across interfaces.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The gateway ignores the destination interface during NAT lookup.
Why it's wrong here
The current value of 0 explicitly instructs the kernel to respect the destination interface definition. If the value were 1, the gateway would ignore the interface, allowing NAT rules to match regardless of where the traffic arrived, provided the source and destination IP addresses match the rule.
- ✓
The gateway must match the destination interface for NAT rules.
Why this is correct
With the parameter set to 0, the NAT policy engine includes the destination interface as a mandatory criteria for matching. If the traffic does not arrive on the interface expected by the policy, the translation rule is bypassed, leading to potential connectivity drops or un-translated traffic flow.
- ✗
The NAT policy is corrupted and needs re-installation.
Why it's wrong here
Kernel parameters are standard configuration items and do not indicate policy corruption. The behavior observed is a direct result of the existing system settings, which define how the gateway interprets and matches traffic against the established NAT rules for various interface-specific traffic flows.
- ✗
NAT rules are processed before interface verification.
Why it's wrong here
NAT rules are part of the security policy evaluation process. When the destination interface is relevant to the policy match, the kernel enforces this check. This parameter specifically alters the evaluation logic, and 0 ensures that the interface remains a strict requirement for successful rule matching.
Visual reference
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Check Point exam blueprint
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