F5-CTS-LTM BIG-IP Local Traffic Manager Practice Question
Exhibit
ltm persistence source-addr /Common/my_source_persist {
timeout 180
mask 255.255.255.0
}Refer to the exhibit. What is the effect of the 'mask' setting in this source address persistence profile?
⚠ Common exam trap
Many examinees think the persistence mask applies to individual host routing rather than grouping entire subnets for session stickiness.
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
✓
It groups clients from the same class C network for persistence.
The mask setting in a source address persistence profile allows the BIG-IP to group clients by subnet rather than individual IP address. By setting the mask to 255.255.255.0, the LTM treats all clients originating from the same /24 network as a single entity for persistence purposes. This is particularly useful in environments where many users share a gateway or proxy, preventing persistence table exhaustion.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It hides the individual client's IP from the backend server.
Why it's wrong here
This is a persistence configuration, not a security or privacy feature. The mask only determines how the LTM groups clients for the persistence table; it does not perform any address translation or header modification that would hide the client's actual IP address from the web server.
- ✓
It groups clients from the same class C network for persistence.
Why this is correct
The 255.255.255.0 mask applies to the source IP, meaning only the first three octets of the client's IP are used to create the persistence record. Consequently, all users within that subnet will be directed to the same pool member, effectively sharing the same session persistence state.
- ✗
It limits the number of connections allowed from each subnet.
Why it's wrong here
Persistence profiles do not regulate connection limits. To limit connections, you must use connection rate limiting features or profiles. The mask is strictly for grouping clients based on their IP prefix for the purpose of maintaining server consistency, not for enforcing traffic volume or connection caps.
- ✗
It causes the LTM to ignore the source IP entirely.
Why it's wrong here
The LTM is not ignoring the source IP; it is using it as part of the persistence key. If it were ignoring the source IP, it would not be a source address persistence profile. The mask explicitly dictates how the LTM processes the IP to determine the grouping logic.
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 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.