101 · Question #68

101 Question #68: Real Exam Question with Answer & Explanation

The correct answer is A: 4. The iRule extracts a 3-character substring from a fixed offset after '?' in the URI as the UIE persistence key; with the provided requests, exactly 4 unique key values are produced, creating a maximum of 4 persistence records.

Section 2: F5 Solutions and Technology

Question

The following iRule is being used within a persistence profile on a virtual server. Assuming the following HTTP requests are made within the same timeout window, what is the maximum number of persistence records that will be created iRule: rule Persist_Universal { when HTTP_REQUEST { persist uie [findstr [HTTP ::uri] "?" 8 3] } Requests:

Options

A4
B3
C10
DIt cannot be determined from the given data.
E5
F1
G0

Explanation

The iRule extracts a 3-character substring from a fixed offset after '?' in the URI as the UIE persistence key; with the provided requests, exactly 4 unique key values are produced, creating a maximum of 4 persistence records.

Common mistakes.

B. 3 records underestimates the result because the given request set contains 4 unique URI substrings that each map to a distinct persistence key.
C. 10 records is too high and would require 10 unique 3-character substrings across the provided requests, which exceeds what the data supports.
D. The maximum is determinable from the listed requests by extracting and counting unique 3-character substrings at the specified offset, so the answer is not indeterminate.
E. 5 records exceeds the number of unique key values extractable from the provided request URIs based on the iRule's extraction logic.
F. 1 record would only occur if all provided requests produced the same 3-character substring at the specified position, which contradicts the given data.
G. 0 records would require the iRule to never fire or always produce an empty key, but valid HTTP_REQUEST events with qualifying URIs will produce non-empty persistence keys.

Concept tested. UIE persistence record creation with iRule findstr extraction

Reference. https://clouddocs.f5.com/api/irules/persist.html

Topics

#iRules#universal persistence#HTTP_REQUEST#persistence records

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