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Why do large files fails to upload to ICAP via F5 BIGIP ASM?
This behavior applies to deployments where F5 BIG-IP ASM is used in front of a MetaDefender ICAP server.
When uploading files through F5 BIG-IP ASM to a MetaDefender ICAP server, files larger than 30 MB fail to upload.
On the F5 BIG-IP ASM, the request is blocked with the violation:
“Request length exceeds defined buffer size”
As a result, the file upload does not reach the MetaDefender ICAP server for scanning.
F5 BIG-IP ASM enforces limits on HTTP request buffering.
The parameter long_request_buffer_size controls the maximum size of HTTP requests that ASM can buffer and inspect.
- Default value: 10 MB
- Maximum supported value: 30 MB
If an HTTP request exceeds the configured buffer size, ASM triggers the violation:
Request length exceeds defined buffer size
When this occurs, ASM blocks the request before it is forwarded to the backend server. Consequently, files larger than the configured limit (for example, 35 MB) are not sent to the MetaDefender ICAP server.
To allow larger uploads, adjust the long_request_buffer_size setting in F5 BIG-IP ASM according to F5’s official guidance.
Refer to the F5 documentation:
If Further Assistance is required, please proceed to log a support case or chatting with our support engineer.
