F5-CTS-LTM BIG-IP Local Traffic Manager Practice Question
Exhibit
ltm persistence source-addr /Common/my_src_persist {
timeout 300
match-across-services enabled
}
ltm virtual /Common/vs_http {
pool /Common/web_pool
persist { /Common/my_src_persist { default yes } }
}Refer to the exhibit. An administrator notices that users connecting to both port 80 and port 443 are being persisted to the same backend server. Why is this occurring?
⚠ Common exam trap
Candidates often confuse source persistence with destination port settings, assuming that traffic arriving on different ports must always be persisted to different pool members regardless of global profile settings.
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 'match-across-services' setting is enabled in the persistence profile.
The persistence profile /Common/my_src_persist has 'match-across-services' enabled. This feature instructs the BIG-IP to ignore the destination port when calculating the persistence record. Consequently, when a client hits the virtual server on port 80, the persistence record is created based on the source IP. When the same client subsequently hits a virtual server on port 443, the BIG-IP identifies the existing persistence entry and directs the traffic to the same pool member.
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 persistence timeout is too high, causing records to overlap across services.
Why it's wrong here
The timeout value of 300 seconds simply determines how long the persistence record remains in the table. It does not dictate whether the record is scoped to a specific service or port; that behavior is governed by the 'match-across-services' setting within the persistence profile configuration.
- ✗
The persistence profile is applied to the virtual server without a mask.
Why it's wrong here
The mask setting in a source-address persistence profile controls the granularity of the IP matching, such as applying persistence to a subnet rather than a single host. It does not control whether persistence is restricted to a specific destination service or port; that is controlled by 'match-across-services'.
- ✓
The 'match-across-services' setting is enabled in the persistence profile.
Why this is correct
Enabling 'match-across-services' forces the BIG-IP to maintain persistence records that are independent of the destination port. This means that once a client is mapped to a server via one virtual server, subsequent requests from that source IP to any virtual server will be sent to the same member.
- ✗
The virtual server is using a shared pool, forcing persistence across services.
Why it's wrong here
Sharing a pool across virtual servers does not automatically force persistence across those services unless the persistence profile itself is configured to ignore the service port. Without 'match-across-services' enabled, the BIG-IP would typically treat the combination of source IP and destination port as the unique persistence key.
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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 F5 exam blueprint
This F5-CTS-LTM practice question is part of Courseiva's free F5 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the F5-CTS-LTM exam.