The answer is that both routes must have the same administrative distance and the same priority (metric). ECMP, or Equal Cost Multi-Path routing on FortiGate, requires these two conditions because the firewall calculates route cost by combining administrative distance and priority; only when both values are identical are the paths considered equal-cost, enabling load balancing across multiple links. On the Fortinet NSE 4 Network Security Professional exam, this concept tests your understanding of how FortiGate selects routes—a common trap is assuming that only the metric matters, but administrative distance must also match for ECMP to activate. A helpful memory tip is to think of "AD and Priority" as the two keys that unlock ECMP: if either key is different, the door stays closed, and one route will dominate.
NSE4 System and Network Administration Practice Question
This NSE4 practice question tests your understanding of system and network administration. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An admin is configuring ECMP (Equal Cost Multi-Path) on a FortiGate with two ISPs. Which TWO conditions must be met for ECMP to load balance traffic across both links? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The routes must have the same priority
ECMP requires that multiple routes to the same destination have equal cost. On FortiGate, the cost is determined by administrative distance (AD) and priority (which is the route metric). Both routes must have the same AD and the same priority to be considered equal-cost and eligible for load balancing. If either value differs, one route will be preferred over the other, and ECMP will not activate.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 routes must be configured with the same metric
Why it's wrong here
Metric is for dynamic routing; static routes use distance.
✓
The routes must have the same priority
Why this is correct
Equal priority ensures both routes are considered.
Related concept
Read the scenario before looking for a memorised answer.
✗
The FortiGate must be in transparent mode
Why it's wrong here
ECMP works in both NAT/Route and transparent modes.
✓
The routes must have the same administrative distance
Why this is correct
Equal distances make routes equally preferred.
Related concept
Read the scenario before looking for a memorised answer.
✗
The routes must point to different next-hop IP addresses
Why it's wrong here
They can point to different next-hops; that is typical for ECMP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse 'metric' (which is the priority value on FortiGate) with 'administrative distance', or assume ECMP requires different next-hop IPs, when in fact the key condition is equal cost (same AD and same priority).
Detailed technical explanation
How to think about this question
FortiGate uses a two-tier cost system: administrative distance (AD) for route source preference (e.g., OSPF AD=110, static AD=10) and priority (metric) for routes from the same source. ECMP is enabled when both AD and priority are identical. By default, FortiGate supports up to 255 ECMP paths per destination. In real-world scenarios, if one ISP link has a higher bandwidth, you can adjust the priority (metric) to make them unequal and disable ECMP, forcing traffic to the preferred link.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
System and Network Administration — This question tests System and Network Administration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The routes must have the same priority — ECMP requires that multiple routes to the same destination have equal cost. On FortiGate, the cost is determined by administrative distance (AD) and priority (which is the route metric). Both routes must have the same AD and the same priority to be considered equal-cost and eligible for load balancing. If either value differs, one route will be preferred over the other, and ECMP will not activate.
What should I do if I get this NSE4 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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