Mar 27, 2026 - For details about updated CVE-2025-53521 (BIG-IP APM vulnerability), refer to K000156741.

Understanding HTTP/2 Activation Modes on BIG-IP

Introduction Activation modes specifies how the BIG-IP system negotiates HTTP/2 protocol: TMSH equivalent: In this article I go slightly deeper to explain how BIG-IP negotiates HTTP/2 conn...
Published Jun 11, 2020
Version 1.0
application delivery
big-ip
http2
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CF-Gallia-MS-NOC
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Apr 24, 2023

Hello Rodrigo_Albuque 

Thanks for your article.

So is there any case that the server doesn't respond the extension ALPN in the Server Hello while we still choose ALPN as Activation Mode?

Because we are actually using ALPN mode in our http/2 profile associated with the VS. However, sometime in the Server Hello packet, we see no extension ALPN and then result the client would use http/1.1 and it causes our issue (error message "ERR_HTTP2_PROTOCOL_ERROR" in customer's browser)

With another connection including ALPN extension in Hello Server packet, client will use http/2 and then everything is ok.

Hope to see your advice.

Thank you in advance.