This article is to further show on how this behaviour looks like from the Proxy policy trace and HTTP debug.
Client is sending the request in HTTP/2 but the server does not support HTTP/2.
Proxy running version 7.3 that supports HTTP/2.
The Proxy policy trace will show the following information on the version requested by the client and supported by the server.
The HTTP Debug below indicates that the server only support HTTP/1.x.
0892.296 HTTP Explicit HTTP INFO HTTP SW 1029DA4EA40 for 1029DA45A40 Notifying client-side connection that upstream is HTTP/1.1 (to restrict concurrent streams), hostname=www.example.com, session=102EB2F2020
"HTTP SW 1029DA4EA40 for 1029DA45A40" means it's HTTP/1.x, where it would be "H2 SW 1029DA4EA40 for 1029DA45A40" if it was HTTP/2.
A policy or rule below need to be applied to disable HTTP/2 for the affected server:
client.connection.ssl_server_name.substring=www.example.com http2.client.accept(no) http2.server.request(no)